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Geologic provinces of the world (USGS)
     Shield      Platform      Orogen      Basin      Large igneous province      Extended crust Oceanic crust:      0–20 Ma      20–65 Ma      >65 Ma
Geology (from the Greek γῆ, , "earth" and λόγος, logos, "speech") is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure, physical properties, dynamics, and history of Earth materials, and the processes by which they are formed, moved, and changed. The field is a major academic discipline, and is also important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards, some engineering fields, and understanding past climates and environments.

Contents

History and etymology

History

A mosquito and a fly in this Baltic amber necklace are between 40 and 60 million years old
The work Peri Lithon (On Stones) by the ancient Greek scholar Theophrastus (372–287 BC), a student of ancient Greek philosopher Aristotle, remained authoritative for a millennium. Peri Lithon was translated into Latin and some other foreign languages. Its interpretation of fossils was the most dominant theory in classical Antiquity and the early Middle Ages, until it was replaced by Avicenna's theory of petrifying fluids (succus lapidificatus) in the late Middle Ages.[1][2] In the Roman period, Pliny the Elder produced a very extensive discussion of many more minerals and metals then widely used for practical ends. He is among the first to correctly identify the origin of amber as a fossilized resin from pine trees by the observation of insects trapped within some pieces. He also laid the basis of crystallography by recognising the octahedral habit of diamond.
Some modern scholars, such as Fielding H. Garrison, are of the opinion that modern geology began in the medieval Islamic world.[3] Abu al-Rayhan al-Biruni (973–1048 AD) was one of the earliest Muslim geologists, whose works included the earliest writings on the geology of India, hypothesizing that the Indian subcontinent was once a sea.[4] Ibn Sina (Avicenna, 981–1037), in particular, made significant contributions to geology and the natural sciences (which he called Attabieyat) along with other natural philosophers such as Ikhwan AI-Safa and many others. He wrote an encyclopaedic work entitled “Kitab al-Shifa” (the Book of Cure, Healing or Remedy from ignorance), in which Part 2, Section 5, contains his essay on Mineralogy and Meteorology, in six chapters: Formation of mountains, The advantages of mountains in the formation of clouds; Sources of water; Origin of earthquakes; Formation of minerals; The diversity of earth’s terrain. These principles were later known in the Renaissance of Europe as the law of superposition of strata, the concept of catastrophism, and the doctrine of uniformitarianism. These concepts were also embodied in the Theory of the Earth by James Hutton in the Eighteenth century C.E. Academics such as Toulmin and Goodfield (1965), commented on Avicenna's contribution: "Around A.D. 1000, Avicenna was already suggesting a hypothesis about the origin of mountain ranges, which in the Christian world, would still have been considered quite radical eight hundred years later".[5] Avicenna's scientific methodology of field observation was also original in the Earth sciences, and remains an essential part of modern geological investigations.[2]
In China, the polymath Shen Kua (1031–1095) formulated a hypothesis for the process of land formation: based on his observation of fossil animal shells in a geological stratum in a mountain hundreds of miles from the ocean, he inferred that the land was formed by erosion of the mountains and by deposition of silt.
William Smith's geologic map of England, Wales, and southern Scotland. Completed in 1815, it was the first national-scale geologic map, and by far the most accurate of its time.[6]
Georg Agricola (1494–1555), a physician, wrote the first systematic treatise about mining and smelting works, De re metallica libri XII, with an appendix Buch von den Lebewesen unter Tage (Book of the Creatures Beneath the Earth). He covered subjects like wind energy, hydrodynamic power, melting cookers, transport of ores, extraction of soda, sulfur and alum, and administrative issues. The book was published in 1556.
Nicolas Steno (1638–1686) is credited with the law of superposition, the principle of original horizontality, and the principle of lateral continuity: three defining principles of stratigraphy. By the 1700s Jean-Étienne Guettard and Nicolas Desmarest hiked central France and recorded their observations on geological maps; Guettard recorded the first observation of the volcanic origins of this part of France.
William Smith (1769–1839) drew some of the first geological maps and began the process of ordering rock strata (layers) by examining the fossils contained in them.[6]
James Hutton is often viewed as the first modern geologist.[7] In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained his theory that the Earth must be much older than had previously been supposed in order to allow enough time for mountains to be eroded and for sediments to form new rocks at the bottom of the sea, which in turn were raised up to become dry land. Hutton published a two-volume version of his ideas in 1795 (Vol. 1, Vol. 2).
The geologist, 19th century painting by Carl Spitzweg
Followers of Hutton were known as Plutonists because they believed that some rocks were formed by vulcanism which is the deposition of lava from volcanoes, as opposed to the Neptunists, who believed that all rocks had settled out of a large ocean whose level gradually dropped over time.
In 1811 Georges Cuvier and Alexandre Brongniart published their explanation of the antiquity of the Earth, inspired by Cuvier's discovery of fossil elephant bones in Paris. To prove this, they formulated the principle of stratigraphic succession of the layers of the earth. They were independently anticipated by William Smith's stratigraphic studies on England and Scotland.
Sir Charles Lyell first published his famous book, Principles of Geology[8], in 1830. Lyell continued to publish new revisions until he died in 1875. The book, which influenced the thought of Charles Darwin, successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earth's history and are still occurring today. In contrast, catastrophism is the theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time.
Plate tectonics – seafloor spreading and continental drift illustrated on relief globe of the Field Museum
Much of 19th-century geology revolved around the question of the Earth's exact age. Estimates varied from a few 100,000 to billions of years.[9] The most significant advance in 20th century geology has been the development of the theory of plate tectonics in the 1960s. Plate tectonic theory arose out of two separate geological observations: seafloor spreading and continental drift. The theory revolutionized the Earth sciences.
The theory of continental drift was proposed by Frank Bursley Taylor in 1908, expanded by Alfred Wegener in 1912 and by Arthur Holmes, but wasn't broadly accepted until the late 1960s when the theory of plate tectonics was developed.

Etymology

The word "geology" was first used by Jean-André Deluc in the year 1778 and introduced as a fixed term by Horace-Bénédict de Saussure in the year 1779. The science was not included in Encyclopædia Britannica's third edition completed in 1797, but had a lengthy entry in the fourth edition completed by 1809.[10] An older meaning of the word was first used by Richard de Bury to distinguish between earthly and theological jurisprudence.

Geologic time

Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earth's history.
The geologic time scale encompasses the history of the Earth.[11] It is bracketed at the young end by the dates of the earliest solar system material at 4.567 Ga[12] (gigaannum: billion years ago) and the age of the Earth at 4.54 Ga[13][14], at the beginning of the informally-recognized Hadean eon. At the young end of the scale, it is bracketed by the present day in the Holocene epoch.

Important milestones

Brief time scale

The second and third timelines are each subsections of their preceding timeline as indicated by asterisks. The Holocene (the latest epoch) is too small to be shown clearly on this timeline.
Millions of Years

Relative and Absolute Dating

Geological events can be given a precise date at a point in time, or they can be related to other events that came before and after them. Geologists use a variety of methods to give both relative and absolute dates to geological events. They then use these dates to find the rates at which processes occur.

Relative dating

Cross-cutting relations can be used to determine the relative ages of rock strata and other geological structures. Explanations: A - folded rock strata cut by a thrust fault; B - large intrusion (cutting through A); C - erosional angular unconformity (cutting off A & B) on which rock strata were deposited; D - volcanic dyke (cutting through A, B & C); E - even younger rock strata (overlying C & D); F - normal fault (cutting through A, B, C & E).
Methods for relative dating were developed when geology first emerged as a formal science. Geologists still use the following principles today as a means to provide information about geologic history and the timing of geologic events.
The principle of intrusive relationships concerns crosscutting intrusions. In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock. There are a number of different types of intrusions, including stocks, laccoliths, batholiths, sills and dikes.
The principle of cross-cutting relationships pertains to the formation of faults and the age of the sequences through which they cut. Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault. Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault.[15]
The principle of inclusions and components states that, with sedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them. For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in the matrix. As a result, xenoliths are older than the rock which contains them.
The principle of uniformitarianism states that the geologic processes observed in operation that modify the Earth's crust at present have worked in much the same way over geologic time.[16] A fundamental principle of geology advanced by the 18th century Scottish physician and geologist James Hutton, is that "the present is the key to the past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now."[citation needed]
The principle of original horizontality states that the deposition of sediments occurs as essentially horizontal beds. Observation of modern marine and non-marine sediments in a wide variety of environments supports this generalization (although cross-bedding is inclined, the overall orientation of cross-bedded units is horizontal).[15]
The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of vertical time line, a partial or complete record of the time elapsed from deposition of the lowest layer to deposition of the highest bed.[15]
The principle of faunal succession is based on the appearance of fossils in sedimentary rocks. As organisms exist at the same time period throughout the world, their presence or (sometimes) absence may be used to provide a relative age of the formations in which they are found. Based on principles laid out by William Smith almost a hundred years before the publication of Charles Darwin's theory of evolution, the principles of succession were developed independently of evolutionary thought. The principle becomes quite complex, however, given the uncertainties of fossilization, the localization of fossil types due to lateral changes in habitat (facies change in sedimentary strata), and that not all fossils may be found globally at the same time.[17]

Absolute dating

Geologists can also give precise absolute dates to geologic events. These dates are useful on their own, and can also be used in conjunction with relative dating methods or to calibrate relative dating methods.[18]
A large advance in geology in the advent of the 20th century was the ability to give precise absolute dates to geologic events through radioactive isotopes and other methods. The advent of isotopic dating changed the understanding of geologic time. Before, geologists could only use fossils to date sections of rock relative to one another. With isotopic dates, absolute dating became possible, and these absolute dates could be applied fossil sequences in which there was datable material, converting the old relative ages into new absolute ages.
For many geologic applications, isotope ratios are measured in minerals that give the amount of time that has passed since a rock passed through its particular closure temperature, the point at which different radiometric isotopes stop diffusing into and out of the crystal lattice.[19][20] These are used in geochronologic and thermochronologic studies. Common methods include uranium-lead dating, potassium-argon dating and argon-argon dating, and uranium-thorium dating. These methods are used for a variety of applications. Dating of lavas and ash layers can help to date stratigraphy and calibrate relative dating techniques. These methods can also be used to determine ages of pluton emplacement. Thermochemical techniques can be used to determine temperature proiles within the crust, the uplift of mountain ranges, and paleotopography.
Fractionation of the lanthanide series elements is used to compute ages since rocks were removed from the mantle.
Other methods are used for more recent events. Optically stimulated luminescence and cosmogenic radionucleide dating are used to date surfaces and/or erosion rates. Dendrochronology can also be used for the dating of landscapes. Radiocarbon dating is used for young organic material.

Geologic Materials

The majority of geological data come from research on solid Earth materials. These typically fall into one of two categories: rock and unconsolidated material.

Rock

This schematic diagram of the rock cycle shows the relationship between magma and sedimentary, metamorphic, and igneous rock
There are three major types of rock: igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between these three types of rock, and magma. When a rock crystallizes from melt (magma and/or lava), it is an igneous rock. This rock can be weathered and eroded, and then redeposited and lithified into a sedimentary rock, or be turned into a metamorphic rock due to heat and pressure that change the mineral content of the rock and give it a characteristic fabric. The sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure, and the metamorphic rock can be weathered, eroded, deposited, and lithified, becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism. All three types of rocks may be re-melted; when this happens, a new magma is formed, from which an igneous rock may once again crystallize.
The majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth.

Unconsolidated material

Geologists also study unlithified material, which typically comes from more recent deposits. Because of this, the study of such material is often known as Quaternary geology, after the recent Quaternary Period. This includes the study of sediment and soils, and is important to some (or many) studies in geomorphology, sedimentology, and paleoclimatology.

Whole-Earth structure

Oceanic-continental convergence resulting in subduction and volcanic arcs illustrates one effect of plate tectonics.

Plate tectonics

On this diagram, subducting slabs are in blue, and continental margins and a few plate boundaries are in red. The blue blob in the cutaway section is the seismically-imaged Farallon Plate, which is subducting beneath North America. The remnants of this plate on the Surface of the Earth are the Juan de Fuca Plate and Explorer plate in the Northwestern USA / Southwestern Canada, and the Cocos Plate on the west coast of Mexico.
In the 1960s, a series of discoveries, the most important of which was seafloor spreading[21][22], showed that the Earth's lithosphere, which includes the crust and rigid uppermost portion of the upper mantle, is separated into a number of tectonic plates that move across the plastically-deforming, solid, upper mantle, which is called the asthenosphere. There is an intimate coupling between the movement of the plates on the surface and the convection of the mantle: oceanic plate motions and mantle convection currents always move in the same direction, because the oceanic lithosphere is the rigid upper thermal boundary layer of the convecting mantle. This coupling between rigid plates moving on the surface of the Earth and the convecting mantle is called plate tectonics.
The development of plate tectonics provided a physical basis for many observations of the solid Earth. Long linear regions of geologic features could be explained as plate boundaries.[23] Mid-ocean ridges, high regions on the seafloor where hydrothermal vents and volcanoes exist, were explained as divergent boundaries, where two plates move apart. Arcs of volcanoes and earthquakes were explained as convergent boundaries, where one plate subducts under another. Transform boundaries, such as the San Andreas fault system, resulted in widespread powerful earthquakes. Plate tectonics also provided a mechanism for Alfred Wegener's theory of continental drift[24], in which the continents move across the surface of the Earth over geologic time. They also provided a driving force for crustal deformation, and a new setting for the observations of structural geology. The power of the theory of plate tectonics lies in its ability to combine all of these observations into a single theory of how the lithosphere moves over the convecting mantle.

Earth structure

Earth layered structure. (1) inner core; (2) outer core; (3) lower mantle; (4) upper mantle; (5) lithosphere; (6) crust
Earth layered structure. Typical wave paths from earthquakes like these gave early seismologists insights into the layered structure of the Earth
Advances in seismology, computer modeling, and mineralogy and crystallography at high temperatures and pressures give insights into the internal composition and structure of the Earth.
Seismologists can use the arrival times of seismic waves in reverse to image the interior of the Earth. Early advances in this field showed the existence of a liquid outer core (where shear waves were not able to propagate) and a dense solid inner core. These advances led to the development of a layered model of the Earth, with a crust and lithosphere on top, the mantle below (separated within itself by seismic discontinuities at 410 and 660 kilometers), and the outer core and inner core below that. More recently, seismologists have been able to create detailed images of wave speeds inside the earth in the same way a doctor images a body in a CT scan. These images have led to a much more detailed view of the interior of the Earth, and have replaced the simplified layered model with a much more dynamic model.
Mineralogists have been able to use the pressure and temperature data from the seismic and modelling studies alongside knowledge of the elemental composition of the Earth at depth to reproduce these conditions in experimental settings and measure changes in crystal structure. These studies explain the chemical changes associated with the major seismic discontinuities in the mantle, and show the crystallographic structures expected in the inner core of the Earth.

Geological evolution of an area

An originally horizontal sequence of sedimentary rocks (in shades of tan) are affected by igneous activity. Deep below the surface are a magma chamber and large associated igneous bodies. The magma chamber feeds the volcano, and sends off shoots of magma that will later crystallize into dikes and sills. Magma also advances upwards to form intrusive igneous bodies. The diagram illustrates both a cinder cone volcano, which releases ash, and a composite volcano, which releases both lava and ash.
An illustration of the three types of faults. Strike-slip faults occur when rock units slide past one another, normal faults occur when rocks are undergoing horizontal extension, and thrust faults occur when rocks are undergoing horizontal shortening.
The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations.
Rock units are first emplaced either by deposition onto the surface or intrusion into the overlying rock. Deposition can occur when sediments settle onto the surface of the Earth and later lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows blanket the surface. Igneous intrusions such as batholiths, laccoliths, dikes, and sills, push upwards into the overlying rock, and crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed. Deformation typically occurs as a result of horizontal shortening, horizontal extension, or side-to-side (strike-slip) motion. These structural regimes broadly relate to convergent boundaries, divergent boundaries, and transform boundaries, respectively, between tectonic plates.
When rock units are placed under horizontal compression, they shorten and become thicker. Because rock units, other than muds, do not significantly change in volume, this is accomplished in two primary ways: through faulting and folding. In the shallow crust, where brittle deformation can occur, thrust faults form, which cause deeper rock to move on top of shallower rock. Because deeper rock is often older, as noted by the principle of superposition, this can result in older rocks moving on top of younger ones. Movement along faults can result in folding, either because the faults are not planar, or because the rock layers are dragged along, forming drag folds, as slip occurs are along the fault. Deeper in the Earth, rocks behave plastically, and fold instead of faulting. These folds can either be those where the material in the center of the fold buckles upwards, creating "antiforms", or where it buckles downwards, creating "synforms". If the tops of the rock units within the folds remain pointing upwards, they are called anticlines and synclines, respectively. If some of the units in the fold are facing downward, the structure is called an overturned anticline or syncline, and if all of the rock units are overturned or the correct up-direction is unknown, they are simply called by the most general terms, antiforms and synforms.
A diagram of folds, indicating an anticline and a syncline.
Even higher pressures and temperatures during horizontal shortening can cause both folding and metamorphism of the rocks. This metamorphism causes changes in the mineral composition of the rocks; creates a foliation, or planar surface, that is related to mineral growth under stress; and can remove signs of the original textures of the rocks, such as bedding in sedimentary rocks, flow features of lavas, and crystal patterns in crystalline rocks.
Extension causes the rock units as a whole to become longer and thinner. This is primarily accomplished through normal faulting and through the ductile stretching and thinning. Normal faults drop rock units that are higher below those that are lower. This typically results in younger units being placed below older units. Stretching of units can result in their thinning; in fact, there is a location within the Maria Fold and Thrust Belt in which the entire sedimentary sequence of the Grand Canyon can be seen over a length of less than a meter. Rocks at the depth to be ductilely stretched are often also metamorphosed. These stretched rocks can also pinch into lenses, known as boudins, after the French word for "sausage", because of their visual similarity.
Where rock units slide past one another, strike-slip faults develop in shallow regions, and become shear zones at deeper depths where the rocks deform ductilely.
Geologic cross-section of Kittatinny Mountain. This cross-section shows metamorphic rocks, overlain by younger sediments deposited after the metamorphic event. These rock units were later folded and faulted during the uplift of the mountain.
The addition of new rock units, both depositionally and intrusively, often occurs during deformation. Faulting and other deformational processes result in the creation of topographic gradients, causing material on the rock unit that is increasing in elevation to be eroded by hillslopes and channels. These sediments are deposited on the rock unit that is going down. Continual motion along the fault maintains the topographic gradient in spite of the movement of sediment, and continues to create accommodation space for the material to deposit. Deformational events are often also associated with volcanism and igneous activity. Volcanic ashes and lavas accumulate on the surface, and igneous intrusions enter from below. Dikes, long, planar igneous intrusions, enter along cracks, and therefore often form in large numbers in areas that are being actively deformed. This can result in the emplacement of dike swarms, such as those that are observable across the Canadian shield, or rings of dikes around the lava tube of a volcano.
All of these processes do not necessarily occur in a single environment, and do not necessarily occur in a single order. The Hawaiian Islands, for example, consist almost entirely of layered basaltic lava flows. The sedimentary sequences of the mid-continental United States and the Grand Canyon in the southwestern United States contain almost-undeformed stacks of sedimentary rocks that have remained in place since Cambrian time. Other areas are much more geologically complex. In the southwestern United States, sedimentary, volcanic, and intrusive rocks have been metamorphosed, faulted, foliated, and folded. Even older rocks, such as the Acasta gneiss of the Slave craton in northwestern Canada, the oldest known rock in the world have been metamorphosed to the point where their origin is undiscernable without laboratory analysis. In addition, these processes can occur in stages. In many places, the Grand Canyon in the southwestern United States being a very visible example, the lower rock units were metamorphosed and deformed, and then deformation ended and the upper, undeformed units were deposited. Although any amount of rock emplacement and rock deformation can occur, and they can occur any number of times, these concepts provide a guide to understanding the geological history of an area.

Methods of geology

Geologists use a number of field, laboratory, and numerical modeling methods to decipher Earth history and understand the processes that occur on and in the Earth. In typical geological investigations, geologists use primary information related to petrology (the study of rocks), stratigraphy (the study of sedimentary layers), and structural geology (the study of positions of rock units and their deformation). In many cases, geologists also study modern soils, rivers, landscapes, and glaciers; investigate past and current life and biogeochemical pathways, and use geophysical methods to investigate the subsurface.

Field methods

A typical USGS field mapping camp in the 1950's
Today, handheld computers with GPS and geographic information systems software are often used in geological field work (digital geologic mapping).
Geological field work varies depending on the task at hand. Typical fieldwork could consist of:

Laboratory methods

A petrographic microscope, which is a optical microscope fitted with cross-polarizing lenses, a conoscopic lens, and compensators (plates of anisotropic materials; gypsum plates and quartz wedges are common), for crystallographic analysis.

Petrology

In addition to the field identification of rocks, petrologists identify rock samples in the laboratory. Two of the primary methods for identifying rocks in the laboratory are through optical microscopy and by using an electron microprobe. In an optical mineralogy analysis, thin sections of rock samples are analyzed through a petrographic microscope, where the minerals can be identified through their different properties in plane-polarized and cross-polarized light, including their birefringence, pleochroism, twinning, and interference properties with a conoscopic lens.[31] In the electron microprobe, individual locations are analyzed for their exact chemical compositions and variation in composition within individual crystals.[32] Stable[33] and radioactive isotope[34] studies provide insight into the geochemical evolution of rock units.
Petrologists use fluid inclusion data[35] and perform high temperature and pressure physical experiments[36] to understand the temperatures and pressures at which different mineral phases appear, and how they change through igneous[37] and metamorphic processes. This research can be extrapolated to the field to understand metamorphic processes and the conditions of crystallization of igneous rocks.[38] This work can also help to explain processes that occur within the Earth, such as subduction and magma chamber evolution.

Structural geology

A diagram of an orogenic wedge. The wedge grows through faulting in the interior and along the main basal fault, called the décollement. It builds its shape into a critical taper, in which the angles within the wedge remain the same as failures inside the material balance failures along the décollement. It is analogous to a bulldozer pushing a pile of dirt, where the bulldozer is the overriding plate.
Structural geologists use microscopic analysis of oriented thin sections of geologic samples to observe the fabric within the rocks which gives information about strain within the crystal structure of the rocks. They also plot and combine measurements of geological structures in order to better understand the orientations of faults and folds in order to reconstruct the history of rock deformation in the area. In addition, they perform analog and numerical experiments of rock deformation in large and small settings.
The analysis of structures is often accomplished by plotting the orientations various features onto stereonets. A stereonet is a stereographic projection of a sphere onto a plane, in which planes are projected as lines and lines are projected as points. These can be used to find the locations of fold axes, relationships between several faults, and relationships between other geologic structures.
Among the most well-known experiments in structural geology are those involving orogenic wedges, which are zones in which mountains are built along convergent tectonic plate boundaries.[39] In the analog versions of these experiments, horizontal layers of sand are pulled along a lower surface into a back stop, which results in realistic-looking patterns of faulting and the growth of a critically-tapered (all angles remain the same) orogenic wedge.[40] Numerical models work in the same way as these analog models, though they are often more sophisticated and can include patterns of erosion and uplift in the mountain belt.[41] This helps to show the relationship between erosion and the shape of the mountain range. These studies can also give useful information about pathways for metamorphism through pressure, temperature, space, and time.[42]

Stratigraphy

Exploration geologists examining a freshly recovered drill core. Chile, 1994
In the laboratory, stratigraphers analyze samples of stratigraphic sections that can be returned from the field, such as those from drill cores.[43] Stratigraphers also analyze data from geophysical surveys that show the locations of stratigraphic units in the subsurface.[44] Geophysical data and well logs can be combined to produce a better view of the subsurface, and stratigraphers often use computer programs to do this in three dimensions.[45] Stratigraphers can then use these data to reconstruct ancient processes occurring on the surface of the Earth,[46] interpret past environments, and locate areas for water, coal, and hydrocarbon extraction.
In the laboratory, biostratigraphers analyze rock samples from outcrop and drill cores for the fossils found in them.[43] These fossils help scientists to date the core and to understand the depositional environment in which the rock units formed. Geochronologists precisely date rocks within the stratigraphic section in order to provide better absolute bounds on the timing and rates of deposition.[47] Magnetic stratigraphers look for signs of magnetic reversals in igneous rock units within the drill cores.[43] Other scientists perform stable isotope studies on the rocks to gain information about past climate.[43]

Planetary geology

Surface of Mars as photographed by the Viking 2 lander December 9, 1977.
With the advent of space exploration in the twentieth century, geologists have begun to look at other planetary bodies in the same way as the Earth. This led to the establishment of the field of planetary geology, sometimes known as Astrogeology, in which geologic principles are applied to other bodies of the solar system.
Although the Greek-language-origin prefix geo refers to Earth, "geology" is often used in conjunction with the names of other planetary bodies when describing their composition and internal processes: examples are "the geology of Mars" and "Lunar geology". Specialised terms such as selenology (studies of the Moon), areology (of Mars), etc., are also in use.
Although planetary geologists are interested in all aspects of the planets, a significant focus is in the search for past or present life on other worlds. This has led to many missions whose purpose (or one of their purposes) is to examine planetary bodies for evidence of life. One of these is the Phoenix lander, which analyzed Martian polar soil for water and chemical and mineralogical constituents related to biological processes.

Applied geology

Economic geology

Economic geologists help locate and manage the Earth's natural resources, such as petroleum and coal, as well as mineral resources, which include metals such as iron, copper, and uranium.

Mining geology

Mining geology consists of the extractions of mineral resources from the Earth. Some resources of economic interests include gemstones, metals, and many minerals such as asbestos, perlite, mica, phosphates, zeolites, clay, pumice, quartz, and silica, as well as elements such as sulfur, chlorine, and helium.

Petroleum geology

Petroleum geologists study locations of the subsurface of the Earth which can contain extractable hydrocarbons, especially petroleum and natural gas. Because many of these reservoirs are found in sedimentary basins[48], they study the formation of these basins, as well as their sedimentary and tectonic evolution and the present-day positions of the rock units.

Engineering geology

Engineering geology is the application of the geologic principles to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are properly addressed.
In the field of civil engineering, geological principles and analyses are used in order to ascertain the mechanical principles of the material on which structures are built. This allows tunnels to be built without collapsing, bridges and skyscrapers to be built with sturdy foundations, and buildings to be built that will not settle in clay and mud.[49]

Hydrology and environmental issues

Geology and geologic principles can be applied to various environmental problems, such as stream restoration, the restoration of brownfields, and the understanding of the interactions between natural habitat and the geologic environment. Groundwater hydrology, or hydrogeology, is used to locate groundwater,[50] which can often provide a ready supply of uncontaminated water and is especially important in arid regions,[51] and to monitor the spread of contaminants in groundwater wells.[50][52]
Geologists also obtain data through stratigraphy, boreholes, core samples, and ice cores. Ice cores[53] and sediment cores[54] are used to for paleoclimate reconstructions, which tell geologists about past and present temperature, precipitation, and sea level across the globe. These data are our primary source of information on global climate change outside of instrumental data.[55]

Natural hazards

Geologists and geophysicists study natural hazards in order to enact safe building codes and warning systems that are used to prevent loss of property and life.[56] Examples of important natural hazards that are pertinent to geology (as opposed those that are mainly or only pertinent to meteorology) are:

Fields or related disciplines

Regional geology

By mountain range

By nations

By planet

See also

Notes

  1. ^ Rudwick, M. J. S. (1985). The Meaning of Fossils: Episodes in the History of Palaeontology. University of Chicago Press. p. 24. ISBN 0226731030. 
  2. ^ a b Munim M. Al-Rawi and Salim Al-Hassani (November 2002). "The Contribution of Ibn Sina (Avicenna) to the development of Earth sciences". FSTC. http://www.muslimheritage.com/uploads/ibnsina.pdf. Retrieved 2008-07-01. 
  3. ^ Fielding H. Garrison wrote in the History of Medicine:
    "The Saracens themselves were the originators not only of algebra, chemistry, and geology, but of many of the so-called improvements or refinements of civilization, such as street lamps, window-panes, fireworks, stringed instruments, cultivated fruits, perfumes, spices, etc."
  4. ^ Abdus Salam (1984), "Islam and Science". In C. H. Lai (1987), Ideals and Realities: Selected Essays of Abdus Salam, 2nd ed., World Scientific, Singapore, pp. 179–213.
  5. ^ Toulmin, S. and Goodfield, J. (1965), ’The Ancestry of science: The Discovery of Time’, Hutchinson & Co., London, p. 64 (see also The Contribution of Ibn Sina to the development of Earth sciences)
  6. ^ a b Simon Winchester ; (2002). The map that changed the world: William Smith and the birth of modern geology. New York, NY: Perennial. ISBN 0060931809. 
  7. ^ James Hutton: The Founder of Modern Geology, American Museum of Natural History
  8. ^ Charles Lyell. (1991). Principles of geology. Chicago: University of Chicago Press. ISBN 9780226497976. 
  9. ^ England, Philip (2007). "John Perry's neglected critique of Kelvin's age for the Earth: A missed opportunity in geodynamics". GSA Today 17: 4. doi:10.1130/GSAT01701A.1. 
  10. ^ Winchester, Simon (2001). The Map that Changed the World. HarperCollins Publishers. pp. 25.  ISBN 0-06-093180-9
  11. ^ International Commission on Stratigraphy
  12. ^ a b Amelin, Y; Krot, An; Hutcheon, Id; Ulyanov, Aa (Sep 2002). "Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions.". Science (New York, N.Y.) 297 (5587): 1678–83. doi:10.1126/science.1073950. ISSN 0036-8075. PMID 12215641. 
  13. ^ a b Patterson, C., 1956. “Age of Meteorites and the Earth.” Geochimica et Cosmochimica Acta 10: p. 230-237.
  14. ^ a b G. Brent Dalrymple (1994). The age of the earth. Stanford, Calif.: Stanford Univ. Press. ISBN 0804723311. 
  15. ^ a b c Olsen, Paul E. (2001). "Steno's Principles of Stratigraphy". Dinosaurs and the History of Life. Columbia University. http://rainbow.ldeo.columbia.edu/courses/v1001/steno.html. Retrieved 2009-03-14. 
  16. ^ Reijer Hooykaas, Natural Law and Divine Miracle: The Principle of Uniformity in Geology, Biology, and Theology, Leiden: EJ Brill, 1963.
  17. ^ As recounted in Simon Winchester, The Map that Changed the World (New York: HarperCollins, 2001), pp. 59-91.
  18. ^ Tucker, R. D.; Bradley, D. C.; Ver Straeten, C. A.; Harris, A. G.; Ebert, J. R.; McCutcheon, S. R. (1998). "New U–Pb zircon ages and the duration and division of Devonian time". Earth and Planetary Science Letters 158: 175. doi:10.1016/S0012-821X(98)00050-8.  edit
  19. ^ Hugh R. Rollinson (1996). Using geochemical data evaluation, presentation, interpretation. Harlow: Longman. ISBN 9780582067011. 
  20. ^ Gunter Faure. (1998). Principles and applications of geochemistry : a comprehensive textbook for geology students. Upper Saddle River, NJ: Prentice-Hall. ISBN 9780023364501. 
  21. ^ H. H. Hess, "History Of Ocean Basins" (November 1, 1962). IN: Petrologic studies: a volume in honor of A. F. Buddington. A. E. J. Engel, Harold L. James, and B. F. Leonard, editors. [New York?]: Geological Society of America, 1962. pp. 599–620.
  22. ^ Kious, Jacquelyne; Tilling, Robert I. (February 1996). "Developing the Theory". This Dynamic Earth: The Story of Plate Tectonics. Kiger, Martha, Russel, Jane (Online ed.). Reston, Virginia, USA: United States Geological Survey. ISBN 0-16-048220-8. http://pubs.usgs.gov/gip/dynamic/understanding.html. Retrieved 13 March 2009. 
  23. ^ Kious, Jacquelyne; Tilling, Robert I. (February 1996). "Understanding Plate Motions". This Dynamic Earth: The Story of Plate Tectonics. Kiger, Martha, Russel, Jane (Online ed.). Reston, Virginia, USA: United States Geological Survey. ISBN 0-16-048220-8. http://pubs.usgs.gov/gip/dynamic/understanding.html. Retrieved 13 March 2009. 
  24. ^ Origin of continents and oceans. S.l.: Dover Pub. 1999. ISBN 0486617084. 
  25. ^ Robert R. Compton. (1985). Geology in the field. New York: Wiley. ISBN 0471829021. 
  26. ^ "USGS Topographic Maps". United States Geological Survey. http://topomaps.usgs.gov/. Retrieved 2009-04-11. 
  27. ^ H. Robert Burger, Anne F. Sheehan, Craig H. Jones. (2006). Introduction to applied geophysics : exploring the shallow subsurface. New York: W.W. Norton. ISBN 0393926370. 
  28. ^ ed. by Wolfgang E. Krumbein (1978). Environmental biogeochemistry and geomicrobiology. Ann Arbor, Mich.: Ann Arbor Science Publ.. ISBN 0250402181. 
  29. ^ Ian McDougall, T. Mark Harrison. (1999). Geochronology and thermochronology by the ♯°Ar/©Ar method. New York: Oxford University Press. ISBN 0195109201. 
  30. ^ Bryn Hubbard, Neil Glasser. (2005). Field techniques in glaciology and glacial geomorphology. Chichester, England: J. Wiley. ISBN 0470844264. 
  31. ^ William D. Nesse. (1991). Introduction to optical mineralogy. New York: Oxford University Press. ISBN 0195060245. 
  32. ^ Morton, ANDREW C. (1985). "A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea". Sedimentology 32: 553. doi:10.1111/j.1365-3091.1985.tb00470.x. 
  33. ^ Zheng, Y (2003). "Stable isotope geochemistry of ultrahigh pressure metamorphic rocks from the Dabie–Sulu orogen in China: implications for geodynamics and fluid regime". Earth-Science Reviews 62: 105. doi:10.1016/S0012-8252(02)00133-2. 
  34. ^ Condomines, M (1995). "Magma dynamics at Mt Etna: Constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas". Earth and Planetary Science Letters 132: 25. doi:10.1016/0012-821X(95)00052-E. 
  35. ^ T.J. Shepherd, A.H. Rankin, D.H.M. Alderton. (1985). A practical guide to fluid inclusion studies. Glasgow: Blackie. ISBN 0412006014. 
  36. ^ Sack, Richard O. (1987). "Experimental petrology of alkalic lavas: constraints on cotectics of multiple saturation in natural basic liquids". Contributions to Mineralogy and Petrology 96: 1. doi:10.1007/BF00375521. 
  37. ^ Alexander R. McBirney. (2007). Igneous petrology. Boston: Jones and Bartlett Publishers. ISBN 9780763734480. 
  38. ^ Frank S. Spear (1995). Metamorphic phase equilibria and pressure-temperature-time paths. Washington, DC: Mineralogical Soc. of America. ISBN 9780939950348. 
  39. ^ Dahlen, F A (1990). "Critical Taper Model of Fold-And-Thrust Belts and Accretionary Wedges". Annual Review of Earth and Planetary Sciences 18: 55. doi:10.1146/annurev.ea.18.050190.000415. 
  40. ^ Gutscher, M (1998). "Material transfer in accretionary wedges from analysis of a systematic series of analog experiments". Journal of Structural Geology 20: 407. doi:10.1016/S0191-8141(97)00096-5. 
  41. ^ Koons, P O (1995). "Modeling the Topographic Evolution of Collisional Belts". Annual Review of Earth and Planetary Sciences 23: 375. doi:10.1146/annurev.ea.23.050195.002111. 
  42. ^ Dahlen, F. A., Suppe, J. & Davis, D. J. geophys. Res. 89, 10087−10101 (1983).
  43. ^ a b c d Hodell, David A. (1994). "Magnetostratigraphic, Biostratigraphic, and Stable Isotope Stratigraphy of an Upper Miocene Drill Core from the Salé Briqueterie (Northwestern Morocco): A High-Resolution Chronology for the Messinian Stage". Paleoceanography 9: 835. doi:10.1029/94PA01838. 
  44. ^ edited by A.W. Bally. (1987). Atlas of seismic stratigraphy. Tulsa, Okla., U.S.A.: American Association of Petroleum Geologists. ISBN 0891810331. 
  45. ^ Fernández, O. (2004). "Three-dimensional reconstruction of geological surfaces: An example of growth strata and turbidite systems from the Ainsa basin (Pyrenees, Spain)". AAPG Bulletin 88: 1049. doi:10.1306/02260403062. 
  46. ^ Poulsen, Chris J. (1998). "Three-dimensional stratigraphic evolution of the Miocene Baltimore Canyon region: Implications for eustatic interpretations and the systems tract model". Geological Society of America Bulletin 110: 1105. doi:10.1130/0016-7606(1998)110<1105:TDSEOT>2.3.CO;2. 
  47. ^ Toscano, M (1999). "Submerged Late Pleistocene reefs on the tectonically-stable S.E. Florida margin: high-precision geochronology, stratigraphy, resolution of Substage 5a sea-level elevation, and orbital forcing.". Quaternary Science Reviews 18: 753. doi:10.1016/S0277-3791(98)00077-8. 
  48. ^ Richard C. Selley. (1998). Elements of petroleum geology. San Diego: Academic Press. ISBN 0-12-636370-6. 
  49. ^ Braja M. Das. (2006). Principles of geotechnical engineering. England: THOMSON LEARNING (KY). ISBN 0534551440. 
  50. ^ a b Hamilton, Pixie A. (1995). "Effects of Agriculture on Ground-Water Quality in Five Regions of the United States". Ground Water 33: 217. doi:10.1111/j.1745-6584.1995.tb00276.x. 
  51. ^ Seckler, David (1999). "Water Scarcity in the Twenty-first Century". International Journal of Water Resources Development 15: 29. doi:10.1080/07900629948916. 
  52. ^ Welch, Alan H. (1988). "Arsenic in Ground Water of the Western United States". Ground Water 26: 333. doi:10.1111/j.1745-6584.1988.tb00397.x. 
  53. ^ Barnola, J. M. (1987). "Vostok ice core provides 160,000-year record of atmospheric CO2". Nature 329: 408. doi:10.1038/329408a0. 
  54. ^ Colman, S.M. (1990). "Holocene paleoclimatic evidence and sedimentation rates from a core in southwestern Lake Michigan". Journal of Paleolimnology 4. doi:10.1007/BF00239699. 
  55. ^ Jones, P. D. (2004). "Climate over past millennia". Reviews of Geophysics 42: RG2002. doi:10.1029/2003RG000143. 
  56. ^ USGS Natural Hazards Gateway

External links

At Wikiversity you can learn more and teach others about Geology at:

Study guide

Up to date as of January 14, 2010
(Redirected to School:Geology article)

From Wikiversity

Welcome to the Geology School!
Jordens inre.svg
A school is a large organizational structure which can contain various departments and divisions. The departments and divisions should be listed in the departments and divisions section. The school should not contain any learning resources. The school can contain projects for developing learning resources.

Divisions and departments

Divisions and Departments of the School exist on pages in "topic" namespace. Start the name of departments with the "Topic:" prefix; departments reside in the Topic: namespace. .Departments and divisions link to learning materials and learning projects.^ The geology department has replaced traditional lectures with project-oriented lectures/labs so that students learn geology in authentic problem-oriented settings.
  • Dickinson College - Geology 16 January 2010 4:31 UTC www.dickinson.edu [Source type: Academic]

Divisions can link subdivisions or to departments. .For more information on schools, divisions and departments look at the Naming Conventions.^ Can I add new entries to the Geographic Names Information System for manmade and administrative features, such as churches, cemeteries, schools, shopping centers, etc.?
  • Welcome to the USGS - U.S. Geological Survey 16 January 2010 4:31 UTC www.usgs.gov [Source type: General]

^ Nate wrote 1 day ago : Every Friday throughout the school year, the Kent State University Department of Geology welcomes gu … more → .
  • Geology — Blogs, Pictures, and more on WordPress 16 January 2010 4:31 UTC en.wordpress.com [Source type: General]

^ For more information on the geology of Ambergris Caye and Belize, click here for a study by Dr. Sal Mazzullo, Department of Geology, Wichita State University.
  • Geology of Belize, Geologic History of Ambergris Caye, Belize 16 January 2010 4:31 UTC ambergriscaye.com [Source type: FILTERED WITH BAYES]

Fields and related disciplines

An illustrated depiction of a syncline and anticline commonly studied in Structural geology and Geomorphology.

Learning projects

Active participants

.The histories of Wikiversity pages indicate who the active participants are.^ I hope my regular visitors will actively participate in the NY Geology Resource Page.
  • New York Geology Resource Forum-Earth Science information, links, and more. 16 January 2010 4:31 UTC newyork.geology-forum.com [Source type: General]

.If you are an active participant in this school, you can list your name here (this can help small schools grow and the participants communicate better; for large schools it is not needed).^ After having gone to a small school where you know everyone and everyone knows you it was quite a change to be at a school where I did not even know all the geology professors let alone students.
  • Alumni (Bowdoin, Geology) 16 January 2010 4:31 UTC www.bowdoin.edu [Source type: FILTERED WITH BAYES]

^ There are a number of resources online and in the department to help you study for the GRE, pick a graduate program, get letters of recommendation, and strengthen your résumé.
  • Blogs | Geology and Astronomy 16 January 2010 4:31 UTC geology.wcupa.edu [Source type: FILTERED WITH BAYES]

^ Moshier are active in their church in Geneva IL, currently helping in the youth (middle school) ministry.
  • Wheaton College (Wheaton, IL) - Geology Faculty 16 January 2010 4:31 UTC www.wheaton.edu [Source type: Academic]

Please remember: if you have an account here people can write you a message also in the future, because IP addresses change !
  • .chantelle
  • Ravi Arya
  • Chrissy
  • Rahul Sharma
  • James89
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  • User:Goodguy007

School news

  • 26 August 2006 - School founded!

External links for learning


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

GEOLOGY (from Gr. .rye, the earth, and X6yos, science), the science which investigates the physical history of the earth.^ X6yos, science), the science which investigates the physical history of the earth.

^ Stratigraphical geology thus gathers up the sum of all that is made known by the other departments of the science, and makes it subservient to the interpretation of the geological history of the earth.

^ This section embraces the evidence supplied by astronomy and physics regarding the form and motions of the earth, the composition of the planets and sun, and the probable history of the solar system .

.Its object is to trace the structural progress of our planet from the earliest beginnings of its separate existence, through its various stages of growth, down to the present condition of things.^ Its object is to trace the structural progress of our planet from the earliest beginnings of its separate existence, through its various stages of growth, down to the present condition of things.

^ Here a brief outline will be given of the gradual growth of geological conceptions from the days of the Greeks and Romans down to modern times, tracing the separate progress of the more important branches of inquiry and noting some of the stages which in each case have led up to the present condition of the science.

^ Up to the present time no definite light has been thrown by physics on the origin and earliest condition of our globe.

.It seeks to determine the manner in which the evolution of the earth's great surface features has been effected.^ It seeks to determine the manner in which the evolution of the earth's great surface features has been effected.

^ Its efficacy in this respect arises partly from its composition, and the chemical reactions which it effects upon the surface of the land, partly from its great variations in temperature and moisture, and partly from its movements.

^ The great plains of the earth's surface are due to this deposit of gravel, sand and loam.

.It unravels the complicated processes by which each continent has been built up.^ It unravels the complicated processes by which each continent has been built up.

^ From geotectonic geology it understands the various processes whereby these materials were put together so as to build up the complicated crust of the earth.

.It follows, even into detail, the varied sculpture of mountain and valley, crag and ravine.^ It follows, even into detail, the varied sculpture of mountain and valley, crag and ravine .

.Nor does it confine itself merely to changes in the inorganic world.^ Nor does it confine itself merely to changes in the inorganic world.

.Geology shows that the present races of plants and animals are the descendants of other and very different races which once peopled the earth.^ Geology shows that the present races of plants and animals are the descendants of other and very different races which once peopled the earth.

^ Photographs and explanations of geology, fossils, soils, plants, and other aspects of the Garland, Texas forest.

^ Part Iv.-Dynamical Geology This section of the science includes the investigation of those processes of change which are at present in progress upon the earth, whereby modifications are made on the structure and composition of the crust, on the relations between the interior and the surface, as shown by volcanoes, earthquakes and other terrestrial disturbances, on the distribution of oceans and continents, on the outlines of the land, on the form and depth of the sea-bottom, on climate, and on the races of plants and animals by which the earth is tenanted.

.It teaches that there has been a progressive development of the inhabitants, as well as one of the globe on which they have dwelt; that each successive period in the earth's history, since the introduction of living things, has been marked by characteristic types of the animal and vegetable kingdoms; and that, however imperfectly the remains of these organisms have been preserved or may be deciphered, materials exist for a history of life upon the planet.^ It teaches that there has been a progressive development of the inhabitants, as well as one of the globe on which they have dwelt; that each successive period in the earth's history, since the introduction of living things, has been marked by characteristic types of the animal and vegetable kingdoms; and that, however imperfectly the remains of these organisms have been preserved or may be deciphered, materials exist for a history of life upon the planet.

^ They have characteristics of both types.
  • VIRTUAL FIELD TRIP 16 January 2010 4:31 UTC www.palomar.edu [Source type: FILTERED WITH BAYES]

^ The worst thing about history is that we have to live with it.
  • Geology 16 January 2010 4:31 UTC rosssea.info [Source type: FILTERED WITH BAYES]

.The geographical distribution of existing faunas and floras is often made clear and intelligible by geological evidence; and in the same way light is thrown upon some of the remoter phases in the history of man himself.^ The geographical distribution of existing faunas and floras is often made clear and intelligible by geological evidence; and in the same way light is thrown upon some of the remoter phases in the history of man himself.

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

^ The roots of ancient volcanoes have thus been laid bare by geological revolutions; and some of the subterranean phases of volcanic action are thereby revealed which are wholly concealed in an active volcano.

.A subject so comprehensive as this must require a wide and varied basis of evidence.^ A subject so comprehensive as this must require a wide and varied basis of evidence.

^ In all speculations of this nature, however, it is necessary to reason from as wide a basis of observation as possible, seeing that so much of the evidence is negative.

.It is one of the characteristics of geology to gather evidence from sources which at first sight seem far removed from its scope, and to seek aid from almost every other leading branch of science.^ It is one of the characteristics of geology to gather evidence from sources which at first sight seem far removed from its scope, and to seek aid from almost every other leading branch of science.

^ If this branch of inquiry, therefore, is to continue worthy of its name as the science of the earth, it must take cognizance of these recent contributions from other sciences.

^ It was in France that this subject first took definite shape as an important branch of science.

.Thus, in dealing with the earliest conditions of the planet, the geologist must fully avail himself of the labours of the astronomer.^ Thus, in dealing with the earliest conditions of the planet, the geologist must fully avail himself of the labours of the astronomer.

^ Its object is to trace the structural progress of our planet from the earliest beginnings of its separate existence, through its various stages of growth, down to the present condition of things.

.Whatever is ascertainable by telescope, spectroscope or chemical analysis, regarding the constitution of other heavenly bodies, has a geological bearing.^ Whatever is ascertainable by telescope , spectroscope or chemical analysis, regarding the constitution of other heavenly bodies, has a geological bearing.

^ Many speculations have been made regarding the chemical composition of the atmosphere during former geological periods.

^ From many chemical analyses, which have been made of these materials, the general chemical constitution ot, at least, the accessible portion of the crust has been satisfactorily ascertained.

.The experiments of the physicist, undertaken to determine conditions of matter and of energy, may sometimes be taken as the starting-points of geological investigation.^ The experiments of the physicist, undertaken to determine conditions of matter and of energy, may sometimes be taken as the starting-points of geological investigation.

^ The early experiments of Sir James Hall, already noticed, formed the starting-point for numerous subsequent researches, which have elucidated many points in the origin and history of rocks.

^ It is manifest , however, that, whatever may have been the original composition of the oceans, they have for a vast section of geological time been constantly receiving mineral matter in solution from the land.

.The work of the chemical laboratory forms the foundation of a vast and increasing mass of geological inquiry.^ The work of the chemical laboratory forms the foundation of a vast and increasing mass of geological inquiry.

^ Introduction to physical and chemical principles of fluid flow and mass transport through geologic media, with emphasis on quantitative characterization of groundwater systems.
  • Rutgers University Earth & Planetary Sciences 16 January 2010 4:31 UTC geology.rutgers.edu [Source type: Academic]

^ Physical- chemical, ore-forming processes and their relation to geologic environment.
  • Rutgers University Earth & Planetary Sciences 16 January 2010 4:31 UTC geology.rutgers.edu [Source type: Academic]

.To the botanist, the zoologist, even to the unscientific, if observant, traveller by land or sea, the geologist turns for information and assistance.^ To the botanist, the zoologist, even to the unscientific, if observant, traveller by land or sea, the geologist turns for information and assistance.

.But while thus culling freely from the dominions of other sciences, geology claims as its peculiar territory the rocky framework of the globe.^ But while thus culling freely from the dominions of other sciences, geology claims as its peculiar territory the rocky framework of the globe.

^ Another branch of physiographical geology which could only come into existence after most of the other departments of the science had made large progress, deals with the evolution of the framework of each country and of the several continents and oceans of the globe.

^ Stratigraphical geology thus gathers up the sum of all that is made known by the other departments of the science, and makes it subservient to the interpretation of the geological history of the earth.

.In the materials composing that framework, their composition and arrangement, the processes of their formation, the changes which they have undergone, and the terrestrial revolutions to which they bear witness, lie the main data of geological history.^ In the materials composing that framework, their composition and arrangement, the processes of their formation, the changes which they have undergone, and the terrestrial revolutions to which they bear witness , lie the main data of geological history.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

^ Where the ice has formed round boulders in shallow water, or at the bottom (" anchor -ice "), it may lift these up when the frost gives way, and may transport them for some distance.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.He finds that they have in large measure arranged themselves in chronological sequence, - the oldest lying at the bottom and the newest at the top.^ He finds that they have in large measure arranged themselves in chronological sequence, - the oldest lying at the bottom and the newest at the top.

^ Besides the limestones, the visible parts of the terrestrial crust are, in large measure, composed of sedimentary rocks which were originally laid down on the sea-bottom.

^ It works out the chronological succession of the great formations of the earth's crust, and endeavours to trace the sequence of events of which they contain the record.

.Relics of an ancient sea-floor are overlain by traces of a vanished land-surface; these are in turn covered by the deposits of a former lake, above which once more appear proofs of the return of the sea.^ Relics of an ancient sea-floor are overlain by traces of a vanished land-surface; these are in turn covered by the deposits of a former lake, above which once more appear proofs of the return of the sea.

^ From the time that any portion of the sea-floor appears above sea-level, it undergoes erosion by the various epigene agents.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

.Among these rocky records lie the lavas and ashes of long-extinct volcanoes.^ Among these rocky records lie the lavas and ashes of long-extinct volcanoes.

^ But the full significance of these extinct types of life could not be understood so long as the doctrine of the immutability of species, so strenuously upheld by Cuvier, maintained its sway among naturalists.

.The ripple lift upon the shore, the cracks formed by the sun's heat upon the muddy bottom of a dried-up pool, the very imprint of the drops of a passing rainshower, have all been accurately preserved, and yield their evidence as to geographical conditions often widely different from those which exist where such markings are now found.^ The ripple lift upon the shore, the cracks formed by the sun's heat upon the muddy bottom of a dried-up pool , the very imprint of the drops of a passing rainshower, have all been accurately preserved, and yield their evidence as to geographical conditions often widely different from those which exist where such markings are now found.

^ This branch of the subject, starting from the evidence supplied by the organic forms which are found preserved in the crust of the earth, includes such questions as the relations between extinct and living types, the laws which appear to have governed the distribution of life in time and in space, the relative importance of different genera of animals in geological inquiry, the nature and use of the evidence from organic remains regarding former conditions of physical geography.

^ Like other observers who had preceded him, he recognized in the various rocks composing the dry land evidence of former geographical conditions very different from those which now prevail.

.But it is mainly by the remains of plants and animals imbedded in the rocks that the geologist is guided in unravelling the chronological succession of geological changes.^ But it is mainly by the remains of plants and animals imbedded in the rocks that the geologist is guided in unravelling the chronological succession of geological changes.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

^ The most important geological function performed by animals is the formation of new deposits out of their remains.

.He has found that a certain order of appearance characterizes these organic remains, that each great group of rocks is marked by its own special types of life, and that these types can be recognized, and the rocks in which they occur can be correlated even in distant countries, and where no other means of comparison would be possible.^ These alternations are to be regarded as following each other in a certain order and periodicity.

^ He has found that a certain order of appearance characterizes these organic remains, that each great group of rocks is marked by its own special types of life, and that these types can be recognized, and the rocks in which they occur can be correlated even in distant countries, and where no other means of comparison would be possible.

^ After patient examination of the rocks, it has been ascertained that every well-marked " formation," or group of strata, is characterized by its own species or genera, or by a general assemblage, or facies, of organic forms.

.At one moment he has to deal with the bones of some large mammal scattered through a deposit of superficial gravel,at another time with the minute foraminifers and ostracods of an upraised sea-bottom.^ At one moment he has to deal with the bones of some large mammal scattered through a deposit of superficial gravel,at another time with the minute foraminifers and ostracods of an upraised sea-bottom.

^ They have been deposited one over another in successive strata from a remote period in the development of the globe down to the present time.

^ These gravel deposits and the bedrock dolomite have been at times incised and then filled with debris only to have the water cut a new channel in a slightly different position as time goes by.
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.Corals and crinoids crowded and crushed into a massive limestone where they lived and died, ferns and terrestrial plants matted together into a bed of coal where they originally grew, the scattered shells of a submarine sand-bank, the snails and lizards which lived and died within a hollow-tree, the insects which have been imprisoned within the exuding resin of old forests, the footprints of birds and quadrupeds, the trails of worms left upon former shores - these, and innumerable other pieces of evidence, enable the geologist to realize in some measure what the faunas and floras of successive periods have been, and what geographical changes the site of every land has undergone.^ Corals and crinoids crowded and crushed into a massive limestone where they lived and died, ferns and terrestrial plants matted together into a bed of coal where they originally grew, the scattered shells of a submarine sand - bank , the snails and lizards which lived and died within a hollow- tree , the insects which have been imprisoned within the exuding resin of old forests, the footprints of birds and quadrupeds, the trails of worms left upon former shores - these, and innumerable other pieces of evidence, enable the geologist to realize in some measure what the faunas and floras of successive periods have been, and what geographical changes the site of every land has undergone.

^ By heedlessly uncovering sand-dunes, and thereby setting in motion a process of destruction which may convert hundreds of acres of fertile land into waste sand, or by prudently planting the dunes with sand-loving vegetation and thus arresting their landward progress.

^ From the evidence thus supplied, it can be shown that the materials ejected from modern submarine volcanic vents closely resemble those accumulated by subaerial volcanoes; that the dust, ashes and stones become intermingled or interstratified with coral -mud, or other non-volcanic deposit of the sea-bottom, that vesicular lavas may be intercalated among them as on land, and that between the successive sheets of volcanic origin, layers of limestone may be laid down which are composed chiefly, or wholly, of the remains of calcareous marine organisms.

.It is evident that to deal successfully with these varied materials, a considerable acquaintance with different branches of science is needful.^ It is evident that to deal successfully with these varied materials, a considerable acquaintance with different branches of science is needful.

^ If this branch of inquiry, therefore, is to continue worthy of its name as the science of the earth, it must take cognizance of these recent contributions from other sciences.

^ He recognized that the various formations differ from each other in their enclosed organic remains, and that from these differences the existence of former sea-bottoms and land surfaces can be determined.

.Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

^ The geological processes of the present time are partly at work underground and partly on the surface of the earth.

^ This branch of the subject, starting from the evidence supplied by the organic forms which are found preserved in the crust of the earth, includes such questions as the relations between extinct and living types, the laws which appear to have governed the distribution of life in time and in space, the relative importance of different genera of animals in geological inquiry, the nature and use of the evidence from organic remains regarding former conditions of physical geography.

.It has often been insisted that the present is the key to the past; and in a wide sense this assertion is eminently true.^ It has often been insisted that the present is the key to the past; and in a wide sense this assertion is eminently true.

^ A knowledge of this branch of the subject is thus the essential groundwork of a true and fruitful acquaintance with the principles of geology, seeing that it necessitates a study of the present order of nature, and thus provides a key for the interpretation of the past.

.Only in proportion as we understand the present, where everything is open on all sides to the fullest investigation, can we expect to decipher the past, where so much is obscure, imperfectly preserved or not preserved at all.^ Only in proportion as we understand the present, where everything is open on all sides to the fullest investigation, can we expect to decipher the past, where so much is obscure, imperfectly preserved or not preserved at all.

^ But only a small proportion of the total marine fauna may be expected to appear in such deposits.

^ Apart from the fact that, even under the most favourable conditions, only a small proportion of the total flora and fauna of any period would be preserved in the fossil state, enormous gaps occur where no record has survived at all.

.A study of the existing economy of nature ought thus to be the foundation of the geologist's training.^ A study of the existing economy of nature ought thus to be the foundation of the geologist's training.

^ Such an inquiry necessitates a careful examination of the existing geological economy of nature, and forms a fitting introduction to an inquiry into the geological changes of former periods.

^ Geognosy thus lays a foundation of knowledge regarding the nature of the materials constituting the mass of the globe, and prepares the way for an investigation of the processes by which these materials are produced and altered.

.While, however, the present condition of things is thus employed, we must obviously be on our guard against the danger of unconsciously assuming that the phase of nature's operations which we now witness has been the same in all past time, that geological changes have always or generally taken place in former ages in the manner and on the scale which we behold to-day, and that at the present time all the great geological processes, which have produced changes in the past eras of the earth's history, are still existent and active.^ This is true to-day, and has, as far as known, been true in all past geological time.

^ The geological processes of the present time are partly at work underground and partly on the surface of the earth.

^ While, however, the present condition of things is thus employed, we must obviously be on our guard against the danger of unconsciously assuming that the phase of nature's operations which we now witness has been the same in all past time, that geological changes have always or generally taken place in former ages in the manner and on the scale which we behold to-day, and that at the present time all the great geological processes, which have produced changes in the past eras of the earth's history, are still existent and active.

.As a working hypothesis we may suppose that the nature of geological processes has remained constant from the beginning; but we cannot postulate that the action of these processes has never varied in energy.^ As a working hypothesis we may suppose that the nature of geological processes has remained constant from the beginning; but we cannot postulate that the action of these processes has never varied in energy.

^ The superficial processes of geology, being much less striking than those of subterranean energy, naturally attracted less attention in antiquity.

^ This subject may be referred to here for the striking evidence which it supplies of the importance of movements of tile earth's crust among geological processes.

.The few centuries wherein man has been observing nature obviously form much too brief an interval by which to measure the intensity of geological action in all past time.^ The few centuries wherein man has been observing nature obviously form much too brief an interval by which to measure the intensity of geological action in all past time.

^ This is true to-day, and has, as far as known, been true in all past geological time.

^ Modern instances are known where, under certain circumstances, submerged trees may last for some centuries, but even the most durable must decay in what, after all, is a brief space of geological time.

.For aught we can tell the present is an era of quietude and slow change, compared with some of the eras which have preceded it.^ For aught we can tell the present is an era of quietude and slow change, compared with some of the eras which have preceded it.

^ We shall always find that the changes we see in action have resulted from some that preceded, and give place to others which follow them.

.Nor perhaps can we be quite sure that, when we have explored every geological process now in progress, we have exhausted all the causes of change which, even in comparatively recent times, have been at work.^ Nor perhaps can we be quite sure that, when we have explored every geological process now in progress, we have exhausted all the causes of change which, even in comparatively recent times, have been at work.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

^ As this gaseous envelope encircles the whole globe it is the most universally present and active of all the agents of geological change.

.In dealing with the geological record, as the accessible solid part of the globe is called, we cannot too vividly realize that at ] the best it forms but an imperfect chronicle.^ In dealing with the geological record, as the accessible solid part of the globe is called, we cannot too vividly realize that at ] the best it forms but an imperfect chronicle.

^ The geological record is at the best but an imperfect chronicle of the geological history of the earth.

^ From all these facts it is clear that the geological record, as it now exists, is at the best but an imperfect chronicle of geological history.

.Geological history cannot be compiled from a full and continuous series of documents.^ Geological history cannot be compiled from a full and continuous series of documents.

^ If, then, geological history is to be compiled from direct evidence furnished by the rocks of the earth, it cannot begin at the beginning of things, but must be content to date its first chapter from the earliest period of which any record has been preserved among the rocks.

.From the very nature of its origin the record is necessarily fragmentary, and it has been further mutilated and obscured by the revolutions of successive ages.^ From the very nature of its origin the record is necessarily fragmentary, and it has been further mutilated and obscured by the revolutions of successive ages.

.And even where the chronicle of events is continuous, it is of very unequal value in different places.^ And even where the chronicle of events is continuous, it is of very unequal value in different places.

.In one case, for example, it may present us with an unbroken succession of deposits many thousands of feet in thickness, from which, however, only a few meagre facts as to geological history can be gleaned.^ In one case, for example, it may present us with an unbroken succession of deposits many thousands of feet in thickness, from which, however, only a few meagre facts as to geological history can be gleaned.

^ The interval between the deposit of two successive laminae of shale may have been as long as, or even longer than, that required for the formation of one of the laminae.

^ Such a chain may be the result of one colossal disturbance; but those of high geological antiquity usually furnish proofs of successive uplifts with more or less intervening denudation.

.In another instance it brings before us, within the compass of a few yards, the evidence of a most varied and complicated series of changes in physical geography, as well as an abundant and interesting suite of organic remains.^ In another instance it brings before us, within the compass of a few yards, the evidence of a most varied and complicated series of changes in physical geography , as well as an abundant and interesting suite of organic remains.

^ This is further evidenced by the larger scale folding on the south wall of the canyon a few hundred yards east up the road.
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^ The stratified portion of the earth's crust, or what has been called the " geological record," can be subdivided into natural groups, or series of strata, characterized by distinctive organic remains and recognizable by these remains, in spite of great changes in lithological character from place to place.

.These and other characteristics of the geological record become more apparent and intelligible as we proceed in the study of the science.^ These and other characteristics of the geological record become more apparent and intelligible as we proceed in the study of the science.

^ The observational records of the action of the sea, of springs, rivers and glaciers are becoming gradually fuller and more trustworthy.

^ If this branch of inquiry, therefore, is to continue worthy of its name as the science of the earth, it must take cognizance of these recent contributions from other sciences.

Table of contents

Classification

.For systematic treatment the subject may be conveniently arranged in the following parts: i.^ For systematic treatment the subject may be conveniently arranged in the following parts: i.

^ But in the systematic treatment of this subject we encounter a difficulty of another kind.

^ The opinions entertained in antiquity on these subjects may be conveniently grouped under two heads: (I) Geological processes now in operation, and (2) geological changes in the past.

.The Historical Development of Geological Science.^ The Historical Development of Geological Science.

^ The following pages thus deal mainly with the general principles and historical development of the science: Part I. - Historical Development Geological Ideas among the Greeks and Romans.

- .Here
a brief outline will be given of the gradual growth of geological conceptions from the days of the Greeks and Romans down to modern times, tracing the separate progress of the more important branches of inquiry and noting some of the stages which in each case have led up to the present condition of the science.^ Historic, up to the present time.

^ As this subject is discussed in a separate article it will be sufficient here to take note of its more important geological bearings .

^ Here a brief outline will be given of the gradual growth of geological conceptions from the days of the Greeks and Romans down to modern times, tracing the separate progress of the more important branches of inquiry and noting some of the stages which in each case have led up to the present condition of the science.

2. The Cosznical Aspects of Geology

.This section embraces the evidence supplied by astronomy and physics regarding the form and motions of the earth, the composition of the planets and sun, and the probable history of the solar system.^ This section embraces the evidence supplied by astronomy and physics regarding the form and motions of the earth, the composition of the planets and sun, and the probable history of the solar system .

^ Terrestrial planet: A planet similar in size and composition to the Earth; especially Mars, Earth, Venus, and Mercury.
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^ They can be tested by an appeal to the crust of the earth, in which the geological history of our planet has been so fully recorded.

.The subjects dealt with under this head are chiefly treated in separate articles.^ The subjects dealt with under this head are chiefly treated in separate articles.

^ The details of this subject will be found in separate articles descriptive of each of the technical terms applied to the several kinds of superinduced structures.

^ In considering this department of geological inquiry it will be convenient to treat it under the following heads: (I) Slow depression and upheaval; (2) Earthquakes; (3) Mountain-making; (4) Metamorphism of rocks.

3. Geognosy

.An inquiry into the materials of the earth's substance.^ An inquiry into the materials of the earth's substance.

^ It embraces an inquiry into the manner in which the various materials composing this crust have been arranged.

.This division, which deals with the parts of the earth, its envelopes of air and water, its solid crust and th e probable condition of its interior, especially treats of the more important minerals of the crust, and the chief rocks of which that crust is built up.^ This division, which deals with the parts of the earth, its envelopes of air and water, its solid crust and th e probable condition of its interior, especially treats of the more important minerals of the crust, and the chief rocks of which that crust is built up.

^ The Investigation Of The Nature And Composition Of The Materials Of Which The Earth Consists This division of the science is devoted to a description of the parts of the earth - of the atmosphere and ocean that surround the planet, and more especially of the solid materials that underlie these envelopes and extend downwards to an unknown distance into the interior.

^ As Darwin first cogently showed, the history of life has been very imperfectly registered in the stratified parts of the earth's crust.

.Geognosy thus lays a foundation of knowledge regarding the nature of the materials constituting the mass of the globe, and prepares the way for an investigation of the processes by which these materials are produced and altered.^ Geognosy thus lays a foundation of knowledge regarding the nature of the materials constituting the mass of the globe, and prepares the way for an investigation of the processes by which these materials are produced and altered.

^ A study of the existing economy of nature ought thus to be the foundation of the geologist's training.

^ Every spring, brook and river removes various salts from the rocks over which it moves, and these substances, thus dissolved, eventually find their way into the sea.

.4. Dynamical Geology studies the nature and working of the various geological processes whereby the rocks of the earth's crust are formed and metamorphosed, and by which changes are effected upon the distribution of sea and land, and upon the forms of terrestrial surfaces.^ The geological processes of the present time are partly at work underground and partly on the surface of the earth.

^ Dynamical Geology studies the nature and working of the various geological processes whereby the rocks of the earth's crust are formed and metamorphosed, and by which changes are effected upon the distribution of sea and land, and upon the forms of terrestrial surfaces.

^ Rain effects two kinds of changes upon the surface of the land.

.Such an inquiry necessitates a careful examination of the existing geological economy of nature, and forms a fitting introduction to an inquiry into the geological changes of former periods.^ Such an inquiry necessitates a careful examination of the existing geological economy of nature, and forms a fitting introduction to an inquiry into the geological changes of former periods.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Many speculations have been made regarding the chemical composition of the atmosphere during former geological periods.

.5. Geotectonic or Structural Geology has for its object the architecture of the earth's crust.^ Geotectonic or Structural Geology has for its object the architecture of the earth's crust.

^ It is the one great object of the geotectonic division of geology to study the structures which have been developed in consequence of earth-movements, and to discover from this investigation the nature of the processes whereby the rocks of the crust have been brought into the condition and the positions in which we now find them.

^ Part V.-Geotectonic Or Structural Geology From a study of the nature and composition of minerals and rocks, and an investigation of the different agencies by which they are formed and modified, the geologist proceeds to inquire how these materials have been put together so as to build up the visible part of the earth's crust.

.It embraces an inquiry into the manner in which the various materials composing this crust have been arranged.^ An inquiry into the materials of the earth's substance.

^ It embraces an inquiry into the manner in which the various materials composing this crust have been arranged.

^ From geotectonic geology it understands the various processes whereby these materials were put together so as to build up the complicated crust of the earth.

.It shows that some have been formed in beds or strata of sediment on the floor of the sea, that others have been built up by the slow aggregation of organic forms, that others have been poured out in a molten condition or in showers of loose dust from subterranean sources.^ It shows that some have been formed in beds or strata of sediment on the floor of the sea, that others have been built up by the slow aggregation of organic forms, that others have been poured out in a molten condition or in showers of loose dust from subterranean sources.

^ Some of its sediment is consequently dropped, and by slow accumulation forms a delta .

^ Their materials have been laid down in laminae, layers and strata, or beds, pointing generally to the intermittent deposition of the sediments of which they consist.

.It further reveals that, though originally laid down in almost horizontal beds, the rocks have subsequently been crumpled, contorted and dislocated, that they have been incessantly worn down, and have often been depressed and buried beneath later accumulations.^ It further reveals that, though originally laid down in almost horizontal beds, the rocks have subsequently been crumpled, contorted and dislocated, that they have been incessantly worn down, and have often been depressed and buried beneath later accumulations.

^ The early experiments of Sir James Hall, already noticed, formed the starting-point for numerous subsequent researches, which have elucidated many points in the origin and history of rocks.

^ Their materials have been laid down in laminae, layers and strata, or beds, pointing generally to the intermittent deposition of the sediments of which they consist.

6. Palaeontological Geology

.This branch of the subject, starting from the evidence supplied by the organic forms which are found preserved in the crust of the earth, includes such questions as the relations between extinct and living types, the laws which appear to have governed the distribution of life in time and in space, the relative importance of different genera of animals in geological inquiry, the nature and use of the evidence from organic remains regarding former conditions of physical geography.^ This branch of the subject, starting from the evidence supplied by the organic forms which are found preserved in the crust of the earth, includes such questions as the relations between extinct and living types, the laws which appear to have governed the distribution of life in time and in space, the relative importance of different genera of animals in geological inquiry, the nature and use of the evidence from organic remains regarding former conditions of physical geography.

^ This subject may be referred to here for the striking evidence which it supplies of the importance of movements of tile earth's crust among geological processes.

^ There are two main purposes to which fossils may be put in geological research: (I) to throw light upon former conditions of physical geography, such as the presence of land, rivers, lakes and seas, in places where they do not now exist, changes of climate, and the former distribution of plants and animals; and (2) to furnish a guide in geological chronology whereby rocks may be classified according to relative date, and the facts of geological history may be arranged and interpreted as a connected record of the earth's progress.

.Some of these problems belong also to zoology and botany, and are more fully discussed in the articles Palaeontology and Palaeobotany.^ Some of these problems belong also to zoology and botany , and are more fully discussed in the articles Palaeontology and Palaeobotany .

^ As this subject is discussed in a separate article it will be sufficient here to take note of its more important geological bearings .

^ The rise of the modern Huttonian school, however, led to a more careful examination of these problems.

7. Stratigraphical Geology

.This section might be called geological history.^ This section might be called geological history.

^ Geologists appear to have reluctantly brought themselves to believe that perhaps, after all, ioo millions of years might suffice for the evolution of geological history.

.It works out the chronological succession of the great formations of the earth's crust, and endeavours to trace the sequence of events of which they contain the record.^ It works out the chronological succession of the great formations of the earth's crust, and endeavours to trace the sequence of events of which they contain the record.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.More particularly, it determines the order of succession of the various plants and animals which in past time have peopled the earth, and thus ascertains what has been the grand march of life upon this planet.^ More particularly, it determines the order of succession of the various plants and animals which in past time have peopled the earth, and thus ascertains what has been the grand march of life upon this planet.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ Geology shows that the present races of plants and animals are the descendants of other and very different races which once peopled the earth.

.8. Physiographical Geology, proceeding from the basis of fact laid down by stratigraphical geology regarding former geographical changes, embraces an inquiry into the origin and history of the features of the earth's surface - continental ridges and ocean basins, plains, valleys and mountains.^ Physiographical Geology, proceeding from the basis of fact laid down by stratigraphical geology regarding former geographical changes, embraces an inquiry into the origin and history of the features of the earth's surface - continental ridges and ocean basins, plains, valleys and mountains.

^ An inquiry into the materials of the earth's substance.

^ Stratigraphical Geology 6 The Cosmogonists and Theories of the Earth 7 Gradual Shaping of Geology into a Distinct Branch of Science 8 Development of Opinion regarding Igneous Rocks 9 Growth of Opinion regarding Earthquakes 10 History of the Evolution of Stratigraphical Geology 11 Rise and Progress of Palaeontological Geology 12 Rise of Physiographical Geology 13 2.

.It explains the causes on which local differences of scenery depend, and shows under what very different circumstances, and at what widely separated intervals, the hills and mountains, even of a single country, have been produced.^ The distinction between hill and mountain depends on the locality.
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^ It explains the causes on which local differences of scenery depend, and shows under what very different circumstances, and at what widely separated intervals, the hills and mountains, even of a single country, have been produced.

^ Geology shows that the present races of plants and animals are the descendants of other and very different races which once peopled the earth.

.Most of the detail embraced in these several sections is relegated to separate articles, to which references are here inserted.^ Most of the detail embraced in these several sections is relegated to separate articles, to which references are here inserted.

^ The details of this subject will be found in separate articles descriptive of each of the technical terms applied to the several kinds of superinduced structures.

^ These and many other early publications are referred to in the Survey Bulletin 71 which is fairly readily available still and so will not be repeated here.
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.The following pages thus deal mainly with the general principles and historical development of the science: Part I. - Historical Development Geological Ideas among the Greeks and Romans.^ The following pages thus deal mainly with the general principles and historical development of the science: Part I. - Historical Development Geological Ideas among the Greeks and Romans.

^ In dealing with the geological record, as the accessible solid part of the globe is called, we cannot too vividly realize that at ] the best it forms but an imperfect chronicle.

^ More recently the principle has been extended to the Palaeozoic formations, though as yet less fully than to the younger parts of the geological record.

- .Many
geological phenomena present themselves in so striking a form that they could hardly fail to impress the imagination of the earliest and rudest races of mankind.^ Many geological phenomena present themselves in so striking a form that they could hardly fail to impress the imagination of the earliest and rudest races of mankind.

^ Geologists were for many years in the habit of believing that no limit could be assigned to the antiquity of the planet, and that they were at liberty to make unlimited drafts on the ages of the past.

^ So, too, the vast beds of coal found all over the world, in geological formations of many different ages, represent so much carbonic acid once present in the air.

.Such incidents as earthquakes and volcanic eruptions, destructive storms on land and sea, disastrous floods and landslips suddenly strewing valleys with ruin, must have awakened the terror of those who witnessed them.^ Such incidents as earthquakes and volcanic eruptions, destructive storms on land and sea, disastrous floods and landslips suddenly strewing valleys with ruin, must have awakened the terror of those who witnessed them.

^ But those who realized most vividly the momentous results achieved by ages of subaerial denudation perceived that, as Hutton showed, even without the aid of underground agency, the mere flow of water in streams across a mass of land must in course of time carve out just such a system of valleys as may anywhere be seen.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.Prominent features of landscape, such as mountain-chains with their snows, clouds and thunderstorms, dark river-chasms that seem purposely cleft open in order to give passage to the torrents that rush through them, crags with their impressive array of pinnacles and recesses must have appealed of old, as they still do, to the awe and wonder of those who for the first time behold them.^ Prominent features of landscape, such as mountain-chains with their snows, clouds and thunderstorms, dark river-chasms that seem purposely cleft open in order to give passage to the torrents that rush through them, crags with their impressive array of pinnacles and recesses must have appealed of old, as they still do, to the awe and wonder of those who for the first time behold them.

^ There is a natural tendency to see in a stupendous piece of scenery, such as a deep ravine, a range of hills, a line of precipice or a chain of mountains, evidence only of subterranean convulsion; and before the subject was taken up as a matter of strict scientific induction , an appeal to former cataclysms was considered a sufficient solution of the problems presented by such features of landscape.

^ That the main features of the land, such as the great mountain-chains, had been produced by gigantic placation of the terrestrial crust was now generally admitted, and also that minor fractures and folds had probably initiated many of the valleys.

.Again, banks of sea-shells in far inland districts would, in course of time, arrest the attention of the more intelligent and reflective observers, and raise in their minds some kind of surmise as to how such shells could ever have come there.^ Again, banks of sea-shells in far inland districts would, in course of time, arrest the attention of the more intelligent and reflective observers, and raise in their minds some kind of surmise as to how such shells could ever have come there.

^ He shows how sensibly the alluvial deposits carried down to the sea increase the breadth of the land, and cites some parts of the shores of the Black Sea, where, in sixty years, the rivers had brought down such a quantity of material that the vessels then in use required to be of much smaller draught than previously, the water shallowing so much that the marshy ground would, in course of time, become dry land.

^ A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia .

.These and other conspicuous geological problems found their earliest solution in legends and myths, wherein the more striking terrestrial features and the elemental forces of nature were represented to be the manifestation of the power of unseen supernatural beings.^ These and other conspicuous geological problems found their earliest solution in legends and myths, wherein the more striking terrestrial features and the elemental forces of nature were represented to be the manifestation of the power of unseen supernatural beings.

^ It was natural, therefore, that the early philosophers of Greece should have noted some of these geological features, and should have sought for other explanations of them than those to be found in the popular myths.

^ No more striking illustration of this feature can be found than that supplied by the Alps, nor one where the geotectonic structures have been so fully studied in detail.

.The basin of the Mediterranean Sea was especially well adapted, from its physical conditions, to be the birth-place of such fables.^ The basin of the Mediterranean Sea was especially well adapted, from its physical conditions, to be the birth-place of such fables.

^ The amount of decay depends partly on conditions of climate, especially the range of temperature, the abundance of moisture, height above the sea and exposure to prevalent winds.

^ Shell-banks are formed abundantly in such comparatively shallow and enclosed basins as that of the North Sea, and on a much more extensive scale on the floor of the West Indian seas.

.It is a region frequently shaken by earthquakes, and contains two distinct centres of volcanic activity, one in the Aegean Sea and one in Italy.^ It is a region frequently shaken by earthquakes, and contains two distinct centres of volcanic activity, one in the Aegean Sea and one in Italy .

^ That it has been left in a state of instability is indicated by the frequent earthquakes of the Alpine region, which doubtless arise from the sudden snapping of rocks under intense strain.

.It is bounded on the north by a long succession of lofty snow-capped mountain-ranges, whence copious rivers, often swollen by heavy rains or melted snows, carry the drainage into the sea.^ It is bounded on the north by a long succession of lofty snow -capped mountain-ranges, whence copious rivers, often swollen by heavy rains or melted snows, carry the drainage into the sea.

^ The access is long, often rough, sometimes washed out by flash floods and the best route in from the north is often blocked by winter snow.
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^ Every spring, brook and river removes various salts from the rocks over which it moves, and these substances, thus dissolved, eventually find their way into the sea.

.On the south it boasts the Nile, once so full of mystery; likewise wide tracts of arid desert with their dreaded dust storms.^ On the south it boasts the Nile , once so full of mystery ; likewise wide tracts of arid desert with their dreaded dust storms.

.The Mediterranean itself, though an inland sea, is subject to gales, which, on exposed coasts, raise breakers quite large enough to give a vivid impression of the power of ocean waves.^ The Mediterranean itself, though an inland sea, is subject to gales, which, on exposed coasts, raise breakers quite large enough to give a vivid impression of the power of ocean waves.

^ Though a long range of such cliffs resembles a coast that has been worn by the sea, it may be entirely due to mere atmospheric waste.

^ The melting of the ice would still further raise the sea-level by the addition of so large a volume of water to the ocean.

.The countries that surround this great sheet of water display in many places widelyspread deposits full of sea shells, like those that still live in the neighbouring bays and gulfs.^ The countries that surround this great sheet of water display in many places widelyspread deposits full of sea shells, like those that still live in the neighbouring bays and gulfs.

^ A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia .

^ More especially noteworthy was a monograph by him which appeared in 1765 bearing the title " On the accidents that have befallen Fossil Shells compared with those which are found to happen to shells now living in the Sea."

.Such a region was not only well fitted to supply subjects for mythology, but also to furnish, on every side, materials which, in their interest and suggestiveness, would appeal to the reason of observant men.^ Such a region was not only well fitted to supply subjects for mythology , but also to furnish, on every side, materials which, in their interest and suggestiveness, would appeal to the reason of observant men.

^ What they do insist on is that the present rate of change is the only one which we can watch and measure, and which will thus supply a statistical basis for any computations on the subject.

^ He had accumulated such conclusive proof of the correctness of his deductions, and had so fully expounded the clearness of the evidence in their favour furnished by the region of Auvergne, that, when any one came to consult him on the subject, he contented himself with giving the advice to " go and see."

.It was natural, therefore, that the early philosophers of Greece should have noted some of these geological features, and should have sought for other explanations of them than those to be found in the popular myths.^ It was natural, therefore, that the early philosophers of Greece should have noted some of these geological features, and should have sought for other explanations of them than those to be found in the popular myths.

^ These and other conspicuous geological problems found their earliest solution in legends and myths, wherein the more striking terrestrial features and the elemental forces of nature were represented to be the manifestation of the power of unseen supernatural beings.

^ No more striking illustration of this feature can be found than that supplied by the Alps, nor one where the geotectonic structures have been so fully studied in detail.

.The opinions entertained in antiquity on these subjects may be conveniently grouped under two heads: (I) Geological processes now in operation, and (2) geological changes in the past.^ The opinions entertained in antiquity on these subjects may be conveniently grouped under two heads: (I) Geological processes now in operation, and (2) geological changes in the past.

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

I. Contemporary Processes. - .The geological processes of the present time are partly at work underground and partly on the surface of the earth.^ The geological processes of the present time are partly at work underground and partly on the surface of the earth.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

.The former, from their frequently disastrous character, received much attention from Greek and Earth" Roman authors.^ The former, from their frequently disastrous character, received much attention from Greek and Earth" Roman authors.

^ The latter receives most attention, as it undoubtedly is the more important; but the former ought not to be omitted in any survey of the general waste of the earth's surface.

.Aristotle, in his Meteorics, cites the speculations of several of his predecessors which he rejects in favour of his own opinion to the effect that earthquakes are due to the generation of wind within the earth, under the influence of the warmth of the sun and the internal heat.^ Aristotle , in his Meteorics, cites the speculations of several of his predecessors which he rejects in favour of his own opinion to the effect that earthquakes are due to the generation of wind within the earth, under the influence of the warmth of the sun and the internal heat.

^ They were styled " formed " or " figured " stones, " lapides sui generis," and were asserted to be due to some inorganic imitative process within the earth or to the influence of the stars.

^ His argument rested on three kinds of evidence: (1) the internal heat and rate of cooling of the earth; (2) the tidal retardation of the earth's rotation; and (3)the origin and age of the sun's heat.

.Wind, being the lightest and most rapidly moving body, is the cause of motion in other bodies, and fire, united with wind, becomes flame, which is endowed with great rapidity of motion.^ Wind, being the lightest and most rapidly moving body, is the cause of motion in other bodies, and fire, united with wind, becomes flame , which is endowed with great rapidity of motion.

^ As to the origin of volcanic outbursts he supposed that the subterranean wind in struggling for an outlet, and whirling through the chasms and passages, meets with great store of sulphur and other combustible substances, which by mere friction are set on fire.

^ The rate of this increase varies, being influenced, among other causes, by the varying conductivity of the rocks.

.Aristotle looked upon earthquakes and volcanic eruptions as closely connected with each other, the discharge of hot materials to the surface being the result of a severe earthquake, when finally the wind rushes out with violence, and sometimes buries the surrounding country under sparks and cinders, as had happened at Lipari.^ Aristotle looked upon earthquakes and volcanic eruptions as closely connected with each other, the discharge of hot materials to the surface being the result of a severe earthquake , when finally the wind rushes out with violence, and sometimes buries the surrounding country under sparks and cinders, as had happened at Lipari.

^ If the surrounding area is composed of material that weather chemically by solution, then the playa is covered with halite (rock salt) and other evaporates.
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^ As the result of these journeys he accumulated materials enough to enable him to produce a geological map of the country, on which the distribution and succession of the rocks were for the first time delineated.

.These crude conceptions of the nature of volcanic action, and the cause of earthquakes, continued to prevail for many centuries.^ These crude conceptions of the nature of volcanic action, and the cause of earthquakes, continued to prevail for many centuries.

^ We have seen how crude were the conceptions of the ancients regarding the causes of volcanic action, and that they connected volcanoes and earthquakes as results of the commotion of wind imprisoned within subterranean caverns and passages.

^ Hence to obtain as complete a conception as possible of the nature and history of volcanic action, regard must be had, not merely to modern volcanoes, but to the records of ancient eruptions which have been preserved within the crust.

.They are repeated by Lucretius, who, however, following Anaximenes, includes as one of the causes of earthquakes the fall of mountainous masses of rock undermined by time, and the consequent propagation of gigantic tremors far and wide through the earth.^ They are repeated by Lucretius , who, however, following Anaximenes , includes as one of the causes of earthquakes the fall of mountainous masses of rock undermined by time, and the consequent propagation of gigantic tremors far and wide through the earth.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.Strabo, having travelled through the volcanic districts of Italy, was able to recognize that Vesuvius had once been an active volcano, although no eruption had taken place from it within human memory.^ Strabo , having travelled through the volcanic districts of Italy, was able to recognize that Vesuvius had once been an active volcano , although no eruption had taken place from it within human memory.

^ Maar volcano: A volcanic crater without a cone, believed to have been formed by an explosive eruption of trapped gases.
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^ Many active volcanoes situated on islands have begun their eruptions below sea-level.

.He continued to hold the belief that volcanic energy arose from the movement of subterranean wind.^ He continued to hold the belief that volcanic energy arose from the movement of subterranean wind.

^ Elastic rebound theory: A theory of fault movement and earthquake generation that holds that faults remain locked while strain energy accumulates in the country rock, and then suddenly slip and release this energy.
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.He believed that the district around the Strait of Messina, which had formerly suffered from destructive earthquakes, was seldom visited by them after the volcanic vents of that region had been opened, so as to provide an escape for the subterranean fire, wind, water and burning masses.^ He believed that the district around the Strait of Messina , which had formerly suffered from destructive earthquakes, was seldom visited by them after the volcanic vents of that region had been opened, so as to provide an escape for the subterranean fire, wind, water and burning masses.

^ Volcanic dome: A rounded accumulation around a volcanic vent of congealed lava too viscous to flow away quickly; hence usually rhyolite lava.
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^ It is supposed that the wholesale destruction of the woodlands formerly existing in countries bordering the Mediterranean has been in part the cause of the present desiccation of these districts.

.He cites in his Geography a number of examples of widespread as well as local sinkings of land, and alludes also to the uprise of the sea-bottom.^ He cites in his Geography a number of examples of widespread as well as local sinkings of land, and alludes also to the uprise of the sea-bottom.

^ On the west side of Japan the land is believed to be sinking below the sea, for fields are replaced by beaches of sand or shingle, while the depth of the sea off shore has perceptibly increased.

^ He recognized that the various formations differ from each other in their enclosed organic remains, and that from these differences the existence of former sea-bottoms and land surfaces can be determined.

.He likewise regards some islands as having been thrown up by volcanic agency, and others as torn from the mainland by such convulsions as earthquakes.^ He likewise regards some islands as having been thrown up by volcanic agency, and others as torn from the mainland by such convulsions as earthquakes.

^ It affirms the interchange of land and sea, the erosion of valleys by descending rivers, the washing down of mountains into the sea, the disappearance of the rivers and the submergence of land by earthquake movements, the separation of some islands from, and the union of others with, the mainland, the uprise of hills by volcanic action, the rise and extinction of burning mountains.

^ He thought that all mountains, except such as were thrown up by volcanic agency or local accidents, have been cut out of plains, the original surfaces of which are indicated by the crests and summits of these elevations.

.The most detailed account of earthquake phenomena which has come down to us from antiquity is that of Seneca in his Quaestiones Naturales. This philosopher had been much interested in the accounts given him by survivors and witnesses of the earthquake which convulsed the district of Naples in February A.D. 63. He distinguished several distinct movements of the ground: 1st, the up and down motion (succussio); 2nd, the oscillatory motion (inclinatio); and probably a third, that of trembling or vibration.^ This philosopher had been much interested in the accounts given him by survivors and witnesses of the earthquake which convulsed the district of Naples in February A.D. 63.

^ He distinguished several distinct movements of the ground: 1st, the up and down motion ( succussio); 2nd, the oscillatory motion ( inclinatio); and probably a third, that of trembling or vibration.

^ The most detailed account of earthquake phenomena which has come down to us from antiquity is that of Seneca in his Quaestiones Naturales.

.While admitting that some earthquakes may arise from the collapse of the walls of subterranean cavities, he adhered to the old idea, held by the most numerous and important previous writers, that these commotions are caused mainly by the movements of wind imprisoned within the earth.^ While admitting that some earthquakes may arise from the collapse of the walls of subterranean cavities, he adhered to the old idea, held by the most numerous and important previous writers, that these commotions are caused mainly by the movements of wind imprisoned within the earth.

^ Earthquake: The violent oscillatory motion of the ground caused by the passage of seismic waves radiating from a fault along which sudden movement has taken place.
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^ We have seen how crude were the conceptions of the ancients regarding the causes of volcanic action, and that they connected volcanoes and earthquakes as results of the commotion of wind imprisoned within subterranean caverns and passages.

.As to the origin of volcanic outbursts he supposed that the subterranean wind in struggling for an outlet, and whirling through the chasms and passages, meets with great store of sulphur and other combustible substances, which by mere friction are set on fire.^ As to the origin of volcanic outbursts he supposed that the subterranean wind in struggling for an outlet, and whirling through the chasms and passages, meets with great store of sulphur and other combustible substances, which by mere friction are set on fire.

^ Not only did the philosopher refrain from availing himself of the high internal temperature of the globe as the source of volcanic energy, he even did not make use of it as the cause of the ignition of his supposed internal fuel, but speculated on the kindling of the subterranean fires by the spirits or gases setting fire to the exhalations, or by the fall of masses of rock and the sparks produced by their friction or percussion.

^ Wind, being the lightest and most rapidly moving body, is the cause of motion in other bodies, and fire, united with wind, becomes flame , which is endowed with great rapidity of motion.

.The elder Pliny reiterates the commonly accepted opinion as to the efficacy of wind underground.^ The elder Pliny reiterates the commonly accepted opinion as to the efficacy of wind underground.

.In discussing the phenomena of earthquakes he remarks that towns with many culverts and houses with cellars suffer less than others, and that at Naples those houses are most shaken which stand on hard ground.^ In discussing the phenomena of earthquakes he remarks that towns with many culverts and houses with cellars suffer less than others, and that at Naples those houses are most shaken which stand on hard ground.

^ The superficial processes of geology, being much less striking than those of subterranean energy, naturally attracted less attention in antiquity.

^ One could thus deduce that water filled this valley less frequently than others.
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.It thus appears that with regard to subterranean geological operations, no advance was made during the time of the Greeks and Romans as to the theoretical explanation of these phenomena; but a considerable body of facts was collected, especially as to the effects of earthquakes and the occurrence of volcanic eruptions.^ It thus appears that with regard to subterranean geological operations, no advance was made during the time of the Greeks and Romans as to the theoretical explanation of these phenomena; but a considerable body of facts was collected, especially as to the effects of earthquakes and the occurrence of volcanic eruptions.

^ From this brief sketch it will be seen that while the ancients had accumulated a good deal of information regarding the occurrence of geological changes, their interpretations of the phenomena were to a considerable extent mere fanciful speculation .

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.The superficial processes of geology, being much less striking than those of subterranean energy, naturally attracted less attention in antiquity.^ The superficial processes of geology, being much less striking than those of subterranean energy, naturally attracted less attention in antiquity.

^ He insists that the time " was more than 20 and less than 40 millions of years and probably much nearer 20 than 40."

^ But we cannot assume it to be much less, and it may possibly have been much more, than the ioo millions of years which Lord Kelvin was at one time willing to concede.'

.The operations of rivers, however, which so Action . intimately affect a human population, were watched with revers more or less care.^ The operations of rivers, however, which so Action .

^ The observational records of the action of the sea, of springs, rivers and glaciers are becoming gradually fuller and more trustworthy.

^ The proportion of suspended mineral matter has been ascertained with more or less precision for a number of rivers.

Herodotus, struck by the amount of alluvial silt brought down annually by the Nile and spread over the flat inundated land, inferred that " Egypt is the gift of the river." Aristotle, in discussing some of the features of rivers, displays considerable acquaintance with the various drainage-systems on the north side of the Mediterranean basin. .He refers to the mountains as condensers of the atmospheric moisture, and shows that the largest rivers rise among the loftiest high grounds.^ He refers to the mountains as condensers of the atmospheric moisture, and shows that the largest rivers rise among the loftiest high grounds.

^ But ranges of hills almost mountainous in their bulk may be formed by the gradual erosion of valleys out of a mass of original high ground, such as a high plateau or tableland.

^ As the wind rises over the mountains, it lifts off the ground and looses its saltating ability and the sand is dropped and dunes form.
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.He shows how sensibly the alluvial deposits carried down to the sea increase the breadth of the land, and cites some parts of the shores of the Black Sea, where, in sixty years, the rivers had brought down such a quantity of material that the vessels then in use required to be of much smaller draught than previously, the water shallowing so much that the marshy ground would, in course of time, become dry land.^ He shows how sensibly the alluvial deposits carried down to the sea increase the breadth of the land, and cites some parts of the shores of the Black Sea, where, in sixty years, the rivers had brought down such a quantity of material that the vessels then in use required to be of much smaller draught than previously, the water shallowing so much that the marshy ground would, in course of time, become dry land.

^ Hence various river-formed or " alluvial " deposits are laid down.

^ It is evident that as deposition and denudation are simultaneous processes, the ascertainment of the rate at which solid material is removed from the surface of the land supplies some necessary information for estimating the rate at which new sedimentary formations are being accumulated on the floor of the sea, and for a computation of the length of time that would be required at the present rate of change for the deposition of all the stratified rocks that enter into the composition of the crust of our globe.

.Strabo supplies further interesting information as to the work of rivers in making their alluvial plains and in pushing their deltas seaward.^ Strabo supplies further interesting information as to the work of rivers in making their alluvial plains and in pushing their deltas seaward.

^ By embanking rivers he confines them to narrow channels, sometimes increasing their scour, and enabling them to carry their sediment further seaward, sometimes causing them to deposit it over the plains and raise their level.

^ But neither of these works is of great scientific importance, though containing much interesting information.

.He remarks that these deltas are prevented from advancing farther outward by the ebb and flow of the tides.^ He remarks that these deltas are prevented from advancing farther outward by the ebb and flow of the tides.

2. Past Processes. - .The abundant well-preserved marine shells exposed among the upraised Tertiary and post-Tertiary deposits in the countries bordering the Mediterranean are not infrequently alluded to in Greek and Latin literature.^ The abundant well-preserved marine shells exposed among the upraised Tertiary and post-Tertiary deposits in the countries bordering the Mediterranean are not infrequently alluded to in Greek and Latin literature.

^ In dealing with the mollusca he considered not merely the living but also the extinct forms, especially the abundant, varied and well-preserved genera and species furnished by the Tertiary deposits of the Paris basin, of which he published descriptions and plates that proved of essential service in the stratigraphical work of Cuvier and Alexandre Brongniart (1770-1847).

^ It is supposed that the wholesale destruction of the woodlands formerly existing in countries bordering the Mediterranean has been in part the cause of the present desiccation of these districts.

.renees. Xenophanes of Colophon (614 B.C.) noticed the occurrence of shells and other marine productions inland among the mountains, and inferred from them that the land had risen out of the sea.^ Xenophanes of Colophon (614 B.C.) noticed the occurrence of shells and other marine productions inland among the mountains, and inferred from them that the land had risen out of the sea.

^ Girolamo Fracastorio (1483-1553) claimed that the shells could never have been left by the Flood, which was a mere temporary inundation, but that they proved the mountains, in which they occur, to have been successively uplifted out of the sea.

^ The chlorides and other salts in the sea may likewise partly represent materials carried down out of the atmosphere in the primitive condensation of the aqueous vapour, though they have been continually increased ever since by contributions from the drainage of the land.

.A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia.^ A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia .

.Herodotus, Eratosthenes, Strato and Strabo noted the vast quantities of fossil shells in different parts of Egypt, together with beds of salt, as evidence that the sea had once spread over the country.^ Herodotus, Eratosthenes, Strato and Strabo noted the vast quantities of fossil shells in different parts of Egypt, together with beds of salt , as evidence that the sea had once spread over the country.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

^ After the revival of learning the ancient problem presented by fossil shells imbedded in the rocks of the interior of many countries received renewed attention.

.But by far the most philosophical opinions on the past mutations of the earth's surface are those expressed by Aristotle in the treatise already cited.^ But by far the most philosophical opinions on the past mutations of the earth's surface are those expressed by Aristotle in the treatise already cited.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ It may be said that the absence of such proof ought not to invalidate the assertion until a far wider area of the earth's surface has been geologically studied.

.Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

^ What we now recognize to be memorials of these former injections and propulsions were all confounded with the rocks of unquestionably aqueous origin.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.These alternations are to be regarded as following each other in a certain order and periodicity.^ These alternations are to be regarded as following each other in a certain order and periodicity.

^ They follow each other in the same general order, but not always with equal definiteness.

.But they are apt to escape our notice because they require successive periods of time, which, compared with our brief existence, are of enormous duration, and because they are brought about so imperceptibly that we fail to detect them in progress.^ But they are apt to escape our notice because they require successive periods of time, which, compared with our brief existence, are of enormous duration, and because they are brought about so imperceptibly that we fail to detect them in progress.

^ They have been deposited one over another in successive strata from a remote period in the development of the globe down to the present time.

^ The study of the progress of denudation at the present time has led to the conclusion that even if the rate of waste were not more rapid than it is to-day, it would yet suffice in a comparatively brief geological period to reduce the dry land to below the sea-level.

.In a celebrated passage in his Metamorphoses, Ovid puts into the mouth of the philosopher Pythagoras an account of what was probably regarded as the Pythagorean view of the subject in the Augustan age.^ In a celebrated passage in his Metamorphoses, Ovid puts into the mouth of the philosopher Pythagoras an account of what was probably regarded as the Pythagorean view of the subject in the Augustan age.

^ He approached the subject from an opposite and less philosophical point of view than that of Lamarck, coming to it with certain preconceived notions, which affected all his subsequent writings.

^ As at present constituted, the atmosphere is regarded as a 1 The subject of the age of the earth has also been discussed by Professor J. Joly and Professor W. J. Sollas.

.It affirms the interchange of land and sea, the erosion of valleys by descending rivers, the washing down of mountains into the sea, the disappearance of the rivers and the submergence of land by earthquake movements, the separation of some islands from, and the union of others with, the mainland, the uprise of hills by volcanic action, the rise and extinction of burning mountains.^ It affirms the interchange of land and sea, the erosion of valleys by descending rivers, the washing down of mountains into the sea, the disappearance of the rivers and the submergence of land by earthquake movements, the separation of some islands from, and the union of others with, the mainland, the uprise of hills by volcanic action, the rise and extinction of burning mountains.

^ He likewise regards some islands as having been thrown up by volcanic agency, and others as torn from the mainland by such convulsions as earthquakes.

^ Much help was derived from the admirable illustrations of land-sculpture and river-erosion supplied from the Western Territories and States of the American Union.

.There was a time before Etna began to glow, and the time is coming when the mountain will cease to burn.^ There was a time before Etna began to glow, and the time is coming when the mountain will cease to burn.

^ The mountain might burn for a long time until at last its store of fuel in the shape of sulphur or bitumen would be exhausted.

.From this brief sketch it will be seen that while the ancients had accumulated a good deal of information regarding the occurrence of geological changes, their interpretations of the phenomena were to a considerable extent mere fanciful speculation.^ From this brief sketch it will be seen that while the ancients had accumulated a good deal of information regarding the occurrence of geological changes, their interpretations of the phenomena were to a considerable extent mere fanciful speculation .

^ It thus appears that with regard to subterranean geological operations, no advance was made during the time of the Greeks and Romans as to the theoretical explanation of these phenomena; but a considerable body of facts was collected, especially as to the effects of earthquakes and the occurrence of volcanic eruptions.

^ Many speculations have been made regarding the chemical composition of the atmosphere during former geological periods.

.They had acquired only a most imperfect conception of the nature and operation of the geological processes; and though many writers realized that the surface of the earth has not always been, and will not always remain, as it is now, they had no glimpse of the vast succession of changes of that surface which have been revealed by geology.^ They had acquired only a most imperfect conception of the nature and operation of the geological processes; and though many writers realized that the surface of the earth has not always been, and will not always remain, as it is now, they had no glimpse of the vast succession of changes of that surface which have been revealed by geology.

^ The examples of this process brought to light in Colorado, Wyoming , Nevada and the other western regions by Newberry, King, Hayden, Powell and other explorers, are among the most striking monuments of geological operations in the world.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

.They built hypotheses on the slenderest basis of fact, and did not realize the necessity of testing or verifying them.^ They built hypotheses on the slenderest basis of fact, and did not realize the necessity of testing or verifying them.

.Progress of Geological Conceptions in the Middle Ages.^ Progress of Geological Conceptions in the Middle Ages .

^ A distinguishing feature of the Huttonian philosophy is to be seen in the breadth of its conceptions regarding the geological operations continually in progress on the surface of the globe.

- .During the centuries that succeeded the fall of the Western empire little progress was made in natural science.^ During the centuries that succeeded the fall of the Western empire little progress was made in natural science.

^ The condition of the science in the middle of the 19th century was well shown by J. L. A. Roth, who in 1861 collected about 1000 trustworthy analyses which up to that time had been made.

^ Another conspicuous feature in the progress of stratigraphy during the second half of the 19th century was displayed by the rise and rapid development of what is known as Glacial geology.

.The schoolmen in the monasteries and other seminaries were content to take their science from the literature of Greece and Rome.^ The schoolmen in the monasteries and other seminaries were content to take their science from the literature of Greece and Rome .

^ In the hands of H. Vogelsang, F. Zirkel, H. Rosenbusch, and a host of other workers in all civilized countries, the literature of this department of the science has grown to a remarkable extent.

^ If this branch of inquiry, therefore, is to continue worthy of its name as the science of the earth, it must take cognizance of these recent contributions from other sciences.

The Arabs, however, not only collected and translated that literature, but in some departments made original observations themselves. .To one of the most illustrious of their number, Avicenna, the translator of Aristotle, a treatise has been ascribed, in which singularly modern ideas are expressed regarding mountains, some of which are there stated to have been produced by an uplifting of the ground, while others have been left prominent, owing to the wearing away of the softer rocks around them.^ Phillips (2008) states that there may have only been one or two connections of Lake Manly with the Owens Valley system at about 70ka or 150ka.
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^ Rock cycle: The geologic cycle, with emphasis on the rocks produced; sedimentary rocks are metamorphosed to metamorphic rocks, or melted to create igneous rocks, and all rocks may be uplifted and eroded to make sediments, which lithify to sedimentary rocks.
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^ This is a good place to view the playa, the bajadas that make up the west margin of the valley and the Black Mountain front with the oldest rocks in the state.
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In either case, it is confessed that the process would demand long tracts of time for its completion.
.After the revival of learning the ancient problem presented by fossil shells imbedded in the rocks of the interior of many countries received renewed attention.^ After the revival of learning the ancient problem presented by fossil shells imbedded in the rocks of the interior of many countries received renewed attention.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

^ Flood , and in the course of the vations regarding the great problem of the origin of fossil shells.

.But the conditions for its solution were no longer what they had been in the days of the philosophers of antiquity.^ But the conditions for its solution were no longer what they had been in the days of the philosophers of antiquity.

^ Geologists were for many years in the habit of believing that no limit could be assigned to the antiquity of the planet, and that they were at liberty to make unlimited drafts on the ages of the past.

^ Some of them, especially those of most recent growth, remain in their original condition and position, but, in proportion to their antiquity, they generally present increasing alteration, until it may no longer be possible to tell what was their pristine state.

.Men were not now free to adopt and teach any doctrine they pleased on the subject.^ Men were not now free to adopt and teach any doctrine they pleased on the subject.

.The Christian church had meanwhile arisen to power all over Europe, and adjudged as heretics all who ventured to impugn any of her dogmas.^ The Christian church had meanwhile arisen to power all over Europe , and adjudged as heretics all who ventured to impugn any of her dogmas.

.She taught that the land and the sea had been separated on the third day of creation, before the appearance of any animal life, which was not created until the fifth day.^ She taught that the land and the sea had been separated on the third day of creation, before the appearance of any animal life, which was not created until the fifth day.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

^ The surface of the land may be densely clothed with forest and abundantly peopled with animal life.

.To assert that the dry land is made up in great part of rocks that were formed in the sea, and are crowded with the remains of animals, was plainly to impugn the veracity of the Bible.^ To assert that the dry land is made up in great part of rocks that were formed in the sea, and are crowded with the remains of animals, was plainly to impugn the veracity of the Bible .

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Hence the rocks of which they form part become disintegrated.

.Again, it had come to be the orthodox belief that only somewhere about 6000 years had elapsed since the time of Adam and Eve.^ Again, it had come to be the orthodox belief that only somewhere about 6000 years had elapsed since the time of Adam and Eve .

^ He thinks that it does not seem extravagant to suppose that Soo to 1000 million years may have elapsed since the birth of the moon."

^ Terrestrial animal life, however, was not introduced until 55,000 or 60,000 years after the beginning of the world or about 15,000 years before our time.

.If any thoughtful observer, impressed with the overwhelming force of the evidence that the fossiliferous formations of the earth's crust must have taken long periods of time for their accumulation, ventured to give public expression to his conviction, he ran considerable risk of being proceeded against as a heretic.^ If any thoughtful observer, impressed with the overwhelming force of the evidence that the fossiliferous formations of the earth's crust must have taken long periods of time for their accumulation , ventured to give public expression to his conviction, he ran considerable risk of being proceeded against as a heretic.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.It was needful, therefore, to find some explanation of the facts of nature, which would not run counter to the ecclesiastical system of the day.^ It was needful, therefore, to find some explanation of the facts of nature, which would not run counter to the ecclesiastical system of the day.

^ It was natural, therefore, that the early philosophers of Greece should have noted some of these geological features, and should have sought for other explanations of them than those to be found in the popular myths.

^ George Christian Fiichsel (1722-1773) in Germany, he would have been able to give to his " epochs " a more definite succession of events and a greater correspondence with the facts of nature.

.Various such interpretations were proposed, doubtless in an honest endeavour at reconciliation.^ Various such interpretations were proposed, doubtless in an honest endeavour at reconciliation.

.Three of these deserve special notice: (1) Many able observers and diligent collectors of fossils persuaded themselves that these objects never belonged to organisms of any kind, but should be regarded as mere " freaks of nature," having no more connexion with any once living creature than the frost patterns on a window.^ Three of these deserve special notice: (1) Many able observers and diligent collectors of fossils persuaded themselves that these objects never belonged to organisms of any kind, but should be regarded as mere " freaks of nature," having no more connexion with any once living creature than the frost patterns on a window .

^ Especially baneful was the belief that these objects were mere sports of nature, and had no connexion with any once living organisms.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

.They were styled " formed " or " figured " stones, " lapides sui generis," and were asserted to be due to some inorganic imitative process within the earth or to the influence of the stars.^ They were styled " formed " or " figured " stones, " lapides sui generis," and were asserted to be due to some inorganic imitative process within the earth or to the influence of the stars.

^ Aristotle , in his Meteorics, cites the speculations of several of his predecessors which he rejects in favour of his own opinion to the effect that earthquakes are due to the generation of wind within the earth, under the influence of the warmth of the sun and the internal heat.

^ It has been pointed out in the part of this article dealing with dynamical geology that one of the most important forms of energy in the evolution of geological processes is to be found in the movements that take place within the crust of the earth.

.(2) Observers who could not resist the evidence of their senses that the fossil shells once belonged to living animals, and who, at the same time, felt the necessity of accounting for the presence of marine organisms in the rocks of which the dry land is largely built up, sought a way out of the difficulty by invoking the Deluge of Noah.^ Observers who could not resist the evidence of their senses that the fossil shells once belonged to living animals, and who, at the same time, felt the necessity of accounting for the presence of marine organisms in the rocks of which the dry land is largely built up, sought a way out of the difficulty by invoking the Deluge of Noah .

^ As this branch of the science deals with the evidence furnished by fossil organic remains as to former geographical conditions, it early attracted observers who, in the superficial beds of marine shells found at some distance from the coast, saw proofs of the former submergence of the land under the sea.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.Here was a catastrophe which, they said, extended over the whole globe, and by which the entire dry land was submerged even up to the tops of the high hills.^ Here was a catastrophe which, they said, extended over the whole globe, and by which the entire dry land was submerged even up to the tops of the high hills.

^ Both Vesuvius and Etna sprang up on the floor of the Mediterranean sea, and have gradually built up their cones into conspicuous parts of the dry land.

^ Though the igneous rocks occupy extensive areas in some countries, they nevertheless cover a much smaller part of the whole surface of the land than is' taken up by the second division or stratified rocks.

.True, it only lasted one hundred and fifty days, but so little were the facts then appreciated that no difficulty seems to have been generally felt in crowding the accumulation of the thousands of feet of fossiliferous formations into that brief space of time.^ True, it only lasted one hundred and fifty days, but so little were the facts then appreciated that no difficulty seems to have been generally felt in crowding the accumulation of the thousands of feet of fossiliferous formations into that brief space of time.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ Modern instances are known where, under certain circumstances, submerged trees may last for some centuries, but even the most durable must decay in what, after all, is a brief space of geological time.

.(3) Some more intelligent men in Italy, recognizing that these interpretations could not be upheld, fell back upon the idea that the rocks in which fossil shells are imbedded might have been heaped up by repeated and vigorous eruptions from volcanic centres.^ Some more intelligent men in Italy, recognizing that these interpretations could not be upheld, fell back upon the idea that the rocks in which fossil shells are imbedded might have been heaped up by repeated and vigorous eruptions from volcanic centres.

^ What we now recognize to be memorials of these former injections and propulsions were all confounded with the rocks of unquestionably aqueous origin.

^ Strabo , having travelled through the volcanic districts of Italy, was able to recognize that Vesuvius had once been an active volcano , although no eruption had taken place from it within human memory.

.Certain modern eruptions in the Aegean Sea and in the Bay of Naples had drawn attention to the rapidity with which hills of considerable size could be piled around an active crater.^ Certain modern eruptions in the Aegean Sea and in the Bay of Naples had drawn attention to the rapidity with which hills of considerable size could be piled around an active crater .

^ Many active volcanoes situated on islands have begun their eruptions below sea-level.

.It was argued that if Monte Nuovo near Naples could have been accumulated to a height of nearly 500 ft.^ It was argued that if Monte Nuovo near Naples could have been accumulated to a height of nearly 500 ft.

in two days, there seemed to be no reason against believing that, during the time of the .Flood, and in the course of the vations regarding the great problem of the origin of fossil shells.^ Flood , and in the course of the vations regarding the great problem of the origin of fossil shells.

^ In England, also, illustrated treatises were published both by men who looked on fossils as mere freaks of nature, and by those who regarded them as proofs of Noah's flood.

^ After the revival of learning the ancient problem presented by fossil shells imbedded in the rocks of the interior of many countries received renewed attention.

.He ridiculed the notion that these objects could have been formed by the influence of the stars, and maintained that they had once belonged to living organisms, and therefore that what is now land was formerly covered by the sea.^ He ridiculed the notion that these objects could have been formed by the influence of the stars, and maintained that they had once belonged to living organisms, and therefore that what is now land was formerly covered by the sea.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

.Girolamo Fracastorio (1483-1553) claimed that the shells could never have been left by the Flood, which was a mere temporary inundation, but that they proved the mountains, in which they occur, to have been successively uplifted out of the sea.^ Girolamo Fracastorio (1483-1553) claimed that the shells could never have been left by the Flood, which was a mere temporary inundation, but that they proved the mountains, in which they occur, to have been successively uplifted out of the sea.

^ At the junction where one could go left to Whitecap Mountain, one can go 1.1 miles west (right) up to the Lost Burro Mine.
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^ It works out the chronological succession of the great formations of the earth's crust, and endeavours to trace the sequence of events of which they contain the record.

.On the other hand, even an accomplished anatomist like Gabriello Falloppio (1523-1562) found it easier to believe that the bones of elephants, teeth of sharks, shells and other fossils were mere earthy inorganic concretions, than that the waters of Noah's Flood could ever have reached as far as Italy.^ On the other hand, even an accomplished anatomist like Gabriello Falloppio (1523-1562) found it easier to believe that the bones of elephants, teeth of sharks, shells and other fossils were mere earthy inorganic concretions, than that the waters of Noah's Flood could ever have reached as far as Italy.

^ Girolamo Fracastorio (1483-1553) claimed that the shells could never have been left by the Flood, which was a mere temporary inundation, but that they proved the mountains, in which they occur, to have been successively uplifted out of the sea.

^ In allowing themselves to believe that geology had nothing to do with questions of cosmogony, they gradually grew up in the conviction that such questions could never be other than mere speculation, interesting or amusing as a theme for the employment of the fancy, but hardly coming within the domain of sober and inductive science.

.By much the most important member of this early band of Italian writers was undoubtedly Nicolas Steno (1631-1687), who, though born in Copenhagen, ultimately settled in Florence.^ By much the most important member of this early band of Italian writers was undoubtedly Nicolas Steno (1631-1687), who, though born in Copenhagen , ultimately settled in Florence .

^ The latter receives most attention, as it undoubtedly is the more important; but the former ought not to be omitted in any survey of the general waste of the earth's surface.

.N . Having made a European reputation as an anatomist, his attention was drawn to geological problems by finding that the rocks of the north of Italy contained what appeared to be sharks' teeth closely resembling those of a dog-fish, of which he had published the anatomy.^ Having made a European reputation as an anatomist, his attention was drawn to geological problems by finding that the rocks of the north of Italy contained what appeared to be sharks' teeth closely resembling those of a dog-fish , of which he had published the anatomy .

^ In interpreting this geological history, he laid great stress on the evidence of the fossils contained in the rocks.

^ Although it first appears to be folded into anticlines and synclines, the rock is actually striking north and dipping towards you.
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.Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ As Darwin first cogently showed, the history of life has been very imperfectly registered in the stratified parts of the earth's crust.

^ More particularly, it determines the order of succession of the various plants and animals which in past time have peopled the earth, and thus ascertains what has been the grand march of life upon this planet.

.I-Ie published in 1669 a small tract, De solido intra solidum naturaliter contento, in which he developed the ideas he had formed of this history from an attentive study of the rocks.^ I-Ie published in 1669 a small tract, De solido intra solidum naturaliter contento, in which he developed the ideas he had formed of this history from an attentive study of the rocks.

^ The early experiments of Sir James Hall, already noticed, formed the starting-point for numerous subsequent researches, which have elucidated many points in the origin and history of rocks.

^ As the crust of the earth contains the " geological record," or stony chronicle from which geology interprets the history of our globe, it forms the main subject of study to the geologist.

.He showed that the stratified formations of the hills and valleys consist of such materials as would be laid down in the form of sediment in turbid water; that where they contain marine productions this water is proved to have been the sea; that diversities in their composition point to commingling of currents, carrying different kinds of sediment of which the heaviest would first sink to the bottom.^ Their materials have been laid down in laminae, layers and strata, or beds, pointing generally to the intermittent deposition of the sediments of which they consist.

^ He showed that the stratified formations of the hills and valleys consist of such materials as would be laid down in the form of sediment in turbid water; that where they contain marine productions this water is proved to have been the sea; that diversities in their composition point to commingling of currents, carrying different kinds of sediment of which the heaviest would first sink to the bottom.

^ He shows how sensibly the alluvial deposits carried down to the sea increase the breadth of the land, and cites some parts of the shores of the Black Sea, where, in sixty years, the rivers had brought down such a quantity of material that the vessels then in use required to be of much smaller draught than previously, the water shallowing so much that the marshy ground would, in course of time, become dry land.

.He made original and important observations on stratification, and laid down some of the fundamental axioms in stratigraphy.^ He made original and important observations on stratification, and laid down some of the fundamental axioms in stratigraphy.

^ Besides the limestones, the visible parts of the terrestrial crust are, in large measure, composed of sedimentary rocks which were originally laid down on the sea-bottom.

^ The Arabs , however, not only collected and translated that literature, but in some departments made original observations themselves.

.He reasoned that as the original position of strata was approximately horizontal, when they are found to be steeply inclined or vertical, or bent into arches, they have been disrupted by subterranean exhalations, or by the falling in of the roofs of underground cavernous spaces.^ He reasoned that as the original position of strata was approximately horizontal, when they are found to be steeply inclined or vertical, or bent into arches, they have been disrupted by subterranean exhalations, or by the falling in of the roofs of underground cavernous spaces.

^ No sooner, however, are they placed in that position than they are attacked by running water, and begin to be hollowed out into systems of valleys.

^ It may occasionally be dug into for a depth of 20 or 30 ft., the quartz crystals and veins retaining their original positions, while the felspar is completely kaolinized.

.It is to this alteration of the original position of the strata that the inequalities of the earth's surface, such as mountains, are to be ascribed, though some have been formed by the outburst of fire, ashes and stones from inside the earth.^ It is to this alteration of the original position of the strata that the inequalities of the earth's surface, such as mountains, are to be ascribed, though some have been formed by the outburst of fire, ashes and stones from inside the earth.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ It may be said that the absence of such proof ought not to invalidate the assertion until a far wider area of the earth's surface has been geologically studied.

.Another effect of the dislocation has been to provide fissures, which serve as outlets for springs.^ Another effect of the dislocation has been to provide fissures, which serve as outlets for springs.

.Steno's anatomical training peculiarly fitted him for dealing authoritatively with the question of the nature and origin of the fossils contained in the rocks.^ Steno's anatomical training peculiarly fitted him for dealing authoritatively with the question of the nature and origin of the fossils contained in the rocks.

^ He named them the Cambrian system , and found them to contain fossils, which, however, lay for some time unexamined by him.

^ In the lowest strata, representing the first age, none of the fossils were believed by him to have any living representatives, and he called these rocks " Primordial."

.He had no hesitation in affirming that, even if no shells had ever been found living in the sea, the internal structure of these fossils would demonstrate that they once formed parts of living animals.^ He had no hesitation in affirming that, even if no shells had ever been found living in the sea, the internal structure of these fossils would demonstrate that they once formed parts of living animals.

^ A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia .

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

.And not only shells, but teeth, bones and skeletons of many kinds of fishes had been quarried out of the rocks, while some of the strata had skulls, horns and teeth of land-animals.^ And not only shells, but teeth, bones and skeletons of many kinds of fishes had been quarried out of the rocks, while some of the strata had skulls, horns and teeth of land-animals.

^ In some cases, on the other hand, they protect rocks from decay, while, by the accumulation of their remains, they give rise to extensive formations both upon the land and in the sea.

^ He recognized that the detritus worn away from the land must be spread out over the floor of the sea, so as to form there strata similar to those that compose most of the dry land.

.Illustrating his general principles by a sketch of what he supposed to have been the past history of Tuscany, he added a series of diagrams which show how clearly he had conceived the essential elements of stratigraphy.^ Illustrating his general principles by a sketch of what he supposed to have been the past history of Tuscany , he added a series of diagrams which show how clearly he had conceived the essential elements of stratigraphy.

^ These brilliant researches, rousing widespread interest in such studies, showed how great a flood of light could be thrown on the past history of the earth and its inhabitants.

^ The interstratified or volcanic series is of special importance in geology, inasmuch as it contains the records of volcanic action during the past history of the globe.

.He thought he could perceive the records of six successive phases in the evolution of the framework of that country, and was inclined to believe that a similar chronological sequence would be found all over the world.^ He thought he could perceive the records of six successive phases in the evolution of the framework of that country, and was inclined to believe that a similar chronological sequence would be found all over the world.

^ Faunal succession: The evolutionary sequence of life forms, especially as recorded by the fossil remains in a stratigraphic sequence.
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^ Another branch of physiographical geology which could only come into existence after most of the other departments of the science had made large progress, deals with the evolution of the framework of each country and of the several continents and oceans of the globe.

.He anticipated the objections that would be brought against his views on account of the insuperable difficulty in granting the length of time that would be required for all the geographical vicissitudes which his interpretation required.^ He anticipated the objections that would be brought against his views on account of the insuperable difficulty in granting the length of time that would be required for all the geographical vicissitudes which his interpretation required.

^ But in all speculations of this kind we must bear in mind that the length of time represented by a given depth of strata is not to be estimated merely from their thickness or lithological character.

^ Lord Kelvin has never dealtwith the geological and palaeontological objections against the limitation of geological time to a few millions of years.

.He thought that many of the fossils must be as old as the time of the general deluge, but he was careful not to indulge in any speculation as to the antiquity of the earth.^ He thought that many of the fossils must be as old as the time of the general deluge, but he was careful not to indulge in any speculation as to the antiquity of the earth.

^ It has accordingly been maintained by many geologists that the axis of rotation must have shifted, and that when the remarkable Arctic assemblage of fossil plants lived the region of their growth must have lain in latitudes much nearer to the equator of the time.

^ But in all speculations of this kind we must bear in mind that the length of time represented by a given depth of strata is not to be estimated merely from their thickness or lithological character.

.To the Italian school, as especially typified in Steno, must be assigned the honour of having thus begun to lay firmly and truly the first foundation stones of the modern science of LMazzaro geology.^ Helped the Science Olympiad Team from Beaverton High School (state champions) prepare for the National competition; their team placed 6th in the nation in geology and 12th overall in science .

^ Medical geology: The application of geologic science to problems of health, especially those relating to mineral sources of toxic or nutritious elements and natural dispersal of toxic pollutants.
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.The same school included Antonio Vallisneri o r o.^ The same school included Antonio Vallisneri o r o.

.(1661-1730), who surpassed his predecessors in his wider and more exact knowledge of the fossiliferous rocks that form the backbone of the Italian peninsula, which he contended were formed during a wide and prolonged submergence of the region, altogether different from the brief deluge of Noah.^ Italian peninsula, which he contended were formed during a wide and prolonged submergence of the region, altogether different from the brief deluge of Noah.

^ The forms of valleys have been governed partly by the structure and composition of the rocks, and partly by the relative potency of the different denuding agents.

^ Cataclastic rock: A breccia of powdered rock formed by crushing and shearing during tectonic movements.
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.There was likewise Lazzaro Moro (1687-1740), who did good service against the diluvialists, but the fundamental feature of his system of nature lay in the preponderant part which, unaware of the great difference between volcanic materials and ordinary sediment, he assigned to volcanic action in the production of the sedimentary rocks of the earth's crust.^ There was likewise Lazzaro Moro (1687-1740), who did good service against the diluvialists, but the fundamental feature of his system of nature lay in the preponderant part which, unaware of the great difference between volcanic materials and ordinary sediment, he assigned to volcanic action in the production of the sedimentary rocks of the earth's crust.

^ Even so late as the middle of the 18th century, as above remarked, such a good observer as Lazzaro Moro drew so little distinction between volcanic and other rocks that he could believe the fossiliferous formations to have been mainly formed of materials ejected from eruptive vents.

^ As Darwin first cogently showed, the history of life has been very imperfectly registered in the stratified parts of the earth's crust.

.He supposed that in the beginning the globe was completely surrounded with water, beneath which the solid earth lay as a smooth ball.^ He supposed that in the beginning the globe was completely surrounded with water, beneath which the solid earth lay as a smooth ball .

^ An envelope of air, termed the atmosphere, which surrounds the whole globe; (2) A lower and less extensive envelope of water, known as the hydrosphere (Gr.

^ But it has been claimed that even a solid spherical globe might develop, under the influence of protracted rotation, such a shape as the earth at present possesses.

.On the third day of creation, however, vast fires were kindled inside the globe, whereby the smooth surface of stone was broken up, and portions of it, appearing above the water, formed the earliest land.^ On the third day of creation, however, vast fires were kindled inside the globe, whereby the smooth surface of stone was broken up, and portions of it, appearing above the water, formed the earliest land.

^ Where the ice has formed round boulders in shallow water, or at the bottom (" anchor -ice "), it may lift these up when the frost gives way, and may transport them for some distance.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.From that time onward, volcanic eruptions succeeded each other, not only on the emerged land, but on the sea-floor, over which the ejected material spread in an ever augmenting thickness of sedimentary strata.^ From that time onward, volcanic eruptions succeeded each other, not only on the emerged land, but on the sea-floor, over which the ejected material spread in an ever augmenting thickness of sedimentary strata.

^ From the time that any portion of the sea-floor appears above sea-level, it undergoes erosion by the various epigene agents.

^ The chlorides and other salts in the sea may likewise partly represent materials carried down out of the atmosphere in the primitive condensation of the aqueous vapour, though they have been continually increased ever since by contributions from the drainage of the land.

.In this way Moro carried the history of the stratified rocks beyond the time of the Flood back to the Creation, which was supposed to have been some 1600 years earlier; and he brought it down to the present day, when fresh sedimentary deposits are continually accumulating.^ In this way Moro carried the history of the stratified rocks beyond the time of the Flood back to the Creation, which was supposed to have been some 1600 years earlier; and he brought it down to the present day, when fresh sedimentary deposits are continually accumulating.

^ He shows how sensibly the alluvial deposits carried down to the sea increase the breadth of the land, and cites some parts of the shores of the Black Sea, where, in sixty years, the rivers had brought down such a quantity of material that the vessels then in use required to be of much smaller draught than previously, the water shallowing so much that the marshy ground would, in course of time, become dry land.

^ It is evident that as deposition and denudation are simultaneous processes, the ascertainment of the rate at which solid material is removed from the surface of the land supplies some necessary information for estimating the rate at which new sedimentary formations are being accumulated on the floor of the sea, and for a computation of the length of time that would be required at the present rate of change for the deposition of all the stratified rocks that enter into the composition of the crust of our globe.

.He thus incurred no censure from the ecclesiastical guardians of the faith, and he succeeded in attracting increased public attention to the problems of geology.^ He thus incurred no censure from the ecclesiastical guardians of the faith, and he succeeded in attracting increased public attention to the problems of geology.

^ The superficial processes of geology, being much less striking than those of subterranean energy, naturally attracted less attention in antiquity.

.The influence of his teaching, however, was subsequently in great part due to the Carmelite friar Generelli, who published an eloquent exposition of Moro's views.^ The influence of his teaching, however, was subsequently in great part due to the Carmelite friar Generelli, who published an eloquent exposition of Moro's views.

^ The diluvialists (those who relied on the hypothesis of the Flood) held the field during the 16th, 17th and a great part of the 18th century.

^ Possessed of great enthusiasm for his subject, clear, methodical and eloquent in his exposition of it, he soon drew around him men from all parts of the world, who repaired to study under the great oracle of what he called geognosy (Gr.

The Cosmogonists and Theories of the Earth

.While in Italy substantial progress was made in collecting information regarding the fossiliferous formations of that country, and in forming conclusions concerning them based upon more or less accurate observations, the tendency to mere fanciful speculation, which could not be wholly repressed in any country, reached a remarkable extravagance in England.^ While in Italy substantial progress was made in collecting information regarding the fossiliferous formations of that country, and in forming conclusions concerning them based upon more or less accurate observations, the tendency to mere fanciful speculation, which could not be wholly repressed in any country, reached a remarkable extravagance in England .

^ The ideas of Descartes regarding planetary evolution were enlarged and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), whose teaching has largely influenced all subsequent speculation centuries that have elapsed since that event, the whole of the fossiliferous rocks might have been deposited.

^ Many speculations have been made regarding the chemical composition of the atmosphere during former geological periods.

.In proportion as materials were yet lacking from which to construct a history of the evolution of our planet in accordance with the teaching of the church, imagination supplied the place of ascertained fact, and there appeared during the last twenty years of the 18th century a group of English cosmogonists, who, by the sensational character of their speculations, aroused general attention both in Britain and on the continent.^ In proportion as materials were yet lacking from which to construct a history of the evolution of our planet in accordance with the teaching of the church, imagination supplied the place of ascertained fact, and there appeared during the last twenty years of the 18th century a group of English cosmogonists, who, by the sensational character of their speculations, aroused general attention both in Britain and on the continent.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

.It may be doubted, however, whether the effect of their writings was not to hinder the advance of true science by diverting men from the observation of nature into barren controversy over unrealities.^ It may be doubted, however, whether the effect of their writings was not to hinder the advance of true science by diverting men from the observation of nature into barren controversy over unrealities.

^ In most great chains, however, the rocks have been so intensely crumpled, and even inverted, that much labour may be required before their true relations can be determined.

^ In all speculations of this nature, however, it is necessary to reason from as wide a basis of observation as possible, seeing that so much of the evidence is negative.

.It is not needful here to do more than mention the names of Thomas Burnet, whose Sacred Theory of the Earth appeared in 1681, and William Whiston, whose New Theory of the Earth was published in 1696. Hardly less fanciful than these writers, though his practical acquaintance with rocks and fossils was infinitely greater, was John Woodward, whose Essay towards a Natural History of the Earth dates from 1695. More important as a contribution to science was the catalogue of the large collection of fossils, which he had made from the rocks of England and which he bequeathed to the university of Cambridge.^ It is not needful here to do more than mention the names of Thomas Burnet , whose Sacred Theory of the Earth appeared in 1681, and William Whiston , whose New Theory of the Earth was published in 1696.

^ This catalogue appeared in 1728-1729 with the title of An attempt towards a Natural H i story of the Fossils of England.

^ Hardly less fanciful than these writers, though his practical acquaintance with rocks and fossils was infinitely greater, was John Woodward , whose Essay towards a Natural History of the Earth dates from 1695.

.This catalogue appeared in 1728-1729 with the title of An attempt towards a Natural H i story of the Fossils of England. A striking contrast to these cosmogonists is furnished by another group, which arose in France and Germany, and gave to the world the first rational ideas concerning the probable primeval evolution of our globe.^ A striking contrast to these cosmogonists is furnished by another group, which arose in France and Germany , and gave to the world the first rational ideas concerning the probable primeval evolution of our globe.

^ This catalogue appeared in 1728-1729 with the title of An attempt towards a Natural H i story of the Fossils of England.

^ In a preliminary Discourse prefixed to his Recherches sur les ossemens fossiles (1821) Cuvier gave an outline of what he conceived to have been the past history of our globe, so far as he had been able to comprehend it from his investigations of the Tertiary formations of France.

.The earliest of these pioneers was the illustrious philosopher Rene Descartes (1596-1650).^ The earliest of these pioneers was the illustrious philosopher Rene Descartes (1596-1650).

.He propounded a scheme of cosmical development in which he represented the earth, like the other planets, to have been originally a mass of glowing material like the sun, and to have gradually cooled on the outside, while still retaining an incandescent, self-luminous nucleus.^ He propounded a scheme of cosmical development in which he represented the earth, like the other planets, to have been originally a mass of glowing material like the sun, and to have gradually cooled on the outside, while still retaining an incandescent, self-luminous nucleus .

^ The oldest known rocks present none of the characters of molten material that has cooled and hardened in the air, like the various forms of recent lava.

^ Other important records of the original conditions of deposit are supplied by ripple-marks, sun-cracks, rain-prints and concretions.

.Yet with this noble conception, which modern science has accepted, Descartes could not shake himself free from the time-honoured error in regard to the origin of volcanic action.^ Yet with this noble conception, which modern science has accepted, Descartes could not shake himself free from the time-honoured error in regard to the origin of volcanic action.

^ Hence to obtain as complete a conception as possible of the nature and history of volcanic action, regard must be had, not merely to modern volcanoes, but to the records of ancient eruptions which have been preserved within the crust.

^ Yet they included granite, gneiss, basalt, porphyry and serpentine , which, even in his own day, were by many observers correctly regarded as of igneous origin.

.He thought that certain exhalations within the earth condense into oil, which, when_ in violent motion, enters into the subterranean cavities, where it passes into a kind of smoke.^ He thought that certain exhalations within the earth condense into oil, which, when_ in violent motion, enters into the subterranean cavities, where it passes into a kind of smoke .

^ These bodies were found to consist of elements all of which had been recognized as entering into the constitution of the earth.

^ Thus, silica and alumina are combined to form the aluminous silicates, which enter so largely into the composition of the crust of the earth.

.This smoke is from time to time ignited by a spark of fire and, pressing violently against its containing walls, gives rise to earthquakes.^ This smoke is from time to time ignited by a spark of fire and, pressing violently against its containing walls, gives rise to earthquakes.

^ From time to time the surface suffers calamitous devastation from earthquakes, when portions of the crust under great strain suddenly give way.

^ He conceived that some kind of " fermentation " takes place within the earth, and that the materials which catch fire and give rise to eruptions or earthquakes are analogous to those that constitute gunpowder .

.If the flame breaks through to the surface at the top of a mountain, it may escape with enormous energy, hurling forth much earth mingled with sulphur or bitumen, and thus producing a volcano.^ If the flame breaks through to the surface at the top of a mountain, it may escape with enormous energy, hurling forth much earth mingled with sulphur or bitumen , and thus producing a volcano.

^ It may be said that the absence of such proof ought not to invalidate the assertion until a far wider area of the earth's surface has been geologically studied.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.The mountain might burn for a long time until at last its store of fuel in the shape of sulphur or bitumen would be exhausted.^ The mountain might burn for a long time until at last its store of fuel in the shape of sulphur or bitumen would be exhausted.

^ There was a time before Etna began to glow, and the time is coming when the mountain will cease to burn.

^ In either case, it is confessed that the process would demand long tracts of time for its completion.

.Not only did the philosopher refrain from availing himself of the high internal temperature of the globe as the source of volcanic energy, he even did not make use of it as the cause of the ignition of his supposed internal fuel, but speculated on the kindling of the subterranean fires by the spirits or gases setting fire to the exhalations, or by the fall of masses of rock and the sparks produced by their friction or percussion.^ Not only did the philosopher refrain from availing himself of the high internal temperature of the globe as the source of volcanic energy, he even did not make use of it as the cause of the ignition of his supposed internal fuel, but speculated on the kindling of the subterranean fires by the spirits or gases setting fire to the exhalations, or by the fall of masses of rock and the sparks produced by their friction or percussion.

^ As to the origin of volcanic outbursts he supposed that the subterranean wind in struggling for an outlet, and whirling through the chasms and passages, meets with great store of sulphur and other combustible substances, which by mere friction are set on fire.

^ The source of this energy is to be sought in the enormous expansive force of the vapours and gases dissolved in the magma.

.The ideas of Descartes regarding planetary evolution were enlarged and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), whose teaching has largely influenced all subsequent speculation centuries that have elapsed since that event, the whole of the fossiliferous rocks might have been deposited.^ The ideas of Descartes regarding planetary evolution were enlarged and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), whose teaching has largely influenced all subsequent speculation centuries that have elapsed since that event, the whole of the fossiliferous rocks might have been deposited.

^ Appealing to a much wider public than Descartes or Leibnitz, and basing his speculations on a wider acquaintance with the organic and inorganic realms of nature, G. L. L. de Buffon (1707-1788) was undoubtedly one of the most influential forces that in Europe guided the growth of geological ideas during the 18th century.

^ It must be conceded, however, that the stress which he laid upon the fact that the rocks of the earth's crust were deposited in a definite order had an important influence in directing attention to this subject, and in preparing the way for a more natural system, based not on mere mineralogical characters, but having regard to the organic remains, which were now being gathered in ever-increasing numbers and variety from stratified formations of many different ages and from all parts of the globe.

.Unfortunately for this hypothesis it ignored the fact that these rocks do not consist of volcanic materials.^ Unfortunately for this hypothesis it ignored the fact that these rocks do not consist of volcanic materials.

^ Stratovolcano: A volcanic cone consisting of both lava and pyroclastic rocks, often conical.
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^ Not only is the coarse detritus reduced in size by the friction of the stones against each other, but, at the same time, these materials abrade the rocks against which they are driven by the current.

.So long as the fundamental question remained in dispute as to the true character and history of the stratified portion of the earth's crust containing organic remains, geology as a science could not begin its existence.^ So long as the fundamental question remained in dispute as to the true character and history of the stratified portion of the earth's crust containing organic remains, geology as a science could not begin its existence.

^ He could distinguish among them an older or Primary series, and a younger or Secondary series; and did not dispute the existence of a Tertiary series claimed by Peter Simon Pallas (1741-1811).

^ The stratified portion of the earth's crust, or what has been called the " geological record," can be subdivided into natural groups, or series of strata, characterized by distinctive organic remains and recognizable by these remains, in spite of great changes in lithological character from place to place.

.The diluvialists (those who relied on the hypothesis of the Flood) held the field during the 16th, 17th and a great part of the 18th century.^ The diluvialists (those who relied on the hypothesis of the Flood) held the field during the 16th, 17th and a great part of the 18th century.

^ One good result of the controversy, however, was to be seen in the large collections of these " formed stones" that were gathered together in the cabinets and museums of the 17th and 18th centuries.

^ In England, also, illustrated treatises were published both by men who looked on fossils as mere freaks of nature, and by those who regarded them as proofs of Noah's flood.

.They were looked on as the champions of orthodoxy; and, on that account, they doubtless wielded much more influence than would have been gained by them from the force of their arguments.^ They were looked on as the champions of orthodoxy; and, on that account, they doubtless wielded much more influence than would have been gained by them from the force of their arguments.

^ Certainly ancient marine sedimentary rocks cover at the present day a much more extensive area than that in which they are now being elaborated.

^ He insists that the time " was more than 20 and less than 40 millions of years and probably much nearer 20 than 40."

.Yet during those ages there were not wanting occasional observers who did good service in combating the prevalent misconceptions, and in preparing the way for the ultimate triumph of truth.^ Yet during those ages there were not wanting occasional observers who did good service in combating the prevalent misconceptions, and in preparing the way for the ultimate triumph of truth.

^ The diluvialists (those who relied on the hypothesis of the Flood) held the field during the 16th, 17th and a great part of the 18th century.

.It was more especially in Italy, where many of the more striking phenomena of geology are conspicuously displayed, that the early pioneers of the science arose, and that for several generations the most marked progress was made towards placing the investigations of the past history of the earth upon a basis of careful observation and scientific deduction.^ X6yos, science), the science which investigates the physical history of the earth.

^ It was more especially in Italy, where many of the more striking phenomena of geology are conspicuously displayed, that the early pioneers of the science arose, and that for several generations the most marked progress was made towards placing the investigations of the past history of the earth upon a basis of careful observation and scientific deduction .

^ Of modern English works, Sir A. Geikie's Text Book of Geology (4th ed., 1903) occupies the first place; the work of T. C. Chamberlin and R. D. Salisbury , Geology; Earth History (3 vols., 1905-1906), is especially valuable for American geology.

.One of the first of these leaders was Leonardo da Vinci (1452-1519), who, da besides his achievements in painting, sculpture, archi tecture and engineering, contributed some notable obser [[[Historical Development]] on the subject.^ One of the first of these leaders was Leonardo da Vinci (1452-1519), who, da besides his achievements in painting , sculpture, archi tecture and engineering, contributed some notable obser [[[Historical Development]] on the subject.

.In his great tract, the Protogaea (published in 1749, thirty-three years after his death), he traced the probable passage of our earth from an original condition of incandescent vapour into that of a smooth molten globe, which, by continuous cooling, acquired an external solid crust and rugose surface.^ In his great tract, the Protogaea (published in 1749, thirty-three years after his death), he traced the probable passage of our earth from an original condition of incandescent vapour into that of a smooth molten globe, which, by continuous cooling, acquired an external solid crust and rugose surface.

^ Looking into the future, he foresaw that, by continued refrigeration, our globe will eventually become colder than ice , and this fair face of nature, with its manifold varieties of plant and animal life, will perish after having existed for 132,000 years.

^ Three chief hypotheses have been propounded: (I) that the nucleus is a molten mass enclosed within a solid shell; (2) that, save in local vesicular spaces which may be filled with molten or gaseous material, the globe is solid and rigid to the centre; (3) that the great body of the nucleus consists of incandescent vapours and gases, especially vaporous iron, which under the gigantic pressure within the earth are so compressed as to confer practical rigidity on the globe as a whole, and that outside this main part of the nucleus the gases pass into a shell of molten magma, which, in turn, shades off outwards into the comparatively thin, cool solidified crust.

.He thought that the more ancient rocks, such as granite and gneiss, might be portions of the earliest outer crust; and that as the external solidification advanced, immense subterranean cavities were left which were filled with air and water.^ He thought that the more ancient rocks, such as granite and gneiss , might be portions of the earliest outer crust; and that as the external solidification advanced, immense subterranean cavities were left which were filled with air and water.

^ Certainly ancient marine sedimentary rocks cover at the present day a much more extensive area than that in which they are now being elaborated.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.By the collapse of the roofs of these caverns, valleys might be originated at the surface, while the solid intervening walls would remain in place and form mountains.^ By the collapse of the roofs of these caverns, valleys might be originated at the surface, while the solid intervening walls would remain in place and form mountains.

^ This is also a good place to examine nearly all of the rocks that form the valley walls of upper Titus Canyon because they can all be found as eroded cobbles and boulders on the floor of the wash.
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^ The afternoon view of Death Valley from the point is great and forms a good compliment to the view from Dante’s View (Site FC5) which is visible across the valley on the summit of the Black Mountains.
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.By the disruption of the crust, enormous bodies of water were launched over the surface of the earth, which swept vast quantities of sediment together, and thus gave rise to sedimentary deposits.^ By the disruption of the crust, enormous bodies of water were launched over the surface of the earth, which swept vast quantities of sediment together, and thus gave rise to sedimentary deposits.

^ Along the central heights the mountains lift themselves towards the sky like the storm-swept crests of vast earth-billows.

^ Yet he saw that the visible crust of the earth consists almost wholly of compound bodies.

.After many vicissitudes of this kind, the terrestrial forces calmed down, and a more stable condition of things was established.^ After many vicissitudes of this kind, the terrestrial forces calmed down, and a more stable condition of things was established.

^ Its object is to trace the structural progress of our planet from the earliest beginnings of its separate existence, through its various stages of growth, down to the present condition of things.

.An important feature in the cosmogony of Leibnitz is the prominent place which he assigned to organic remains in the stratified rocks of the crust.^ An important feature in the cosmogony of Leibnitz is the prominent place which he assigned to organic remains in the stratified rocks of the crust.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

^ To the geologist the presence of mineral solutions in sea-water is a fact of much importance, for it explains the origin of a considerable part of the stratified rocks of the earth's crust.

.Ridiculing the foolish attempts to account for the presence of these objects by calling them " sports of nature," he showed that they are to be regarded as historical monuments; and he adduced a number of instances wherein successive platforms of strata, containing organic remains, bear witness to a series of advances and retreats of the sea.^ Ridiculing the foolish attempts to account for the presence of these objects by calling them " sports of nature," he showed that they are to be regarded as historical monuments; and he adduced a number of instances wherein successive platforms of strata, containing organic remains, bear witness to a series of advances and retreats of the sea.

^ The stratified portion of the earth's crust, or what has been called the " geological record," can be subdivided into natural groups, or series of strata, characterized by distinctive organic remains and recognizable by these remains, in spite of great changes in lithological character from place to place.

^ They have been deposited one over another in successive strata from a remote period in the development of the globe down to the present time.

.He recognized that some of the fossils appeared to have nothing like them in the living world of to-day, but some analogous forms might yet be found, he thought, in still unexplored parts of the earth; and even if no living representatives should ever be discovered, many types of animals might have undergone transformation during the great changes which had affected the surface of the earth.^ He recognized that some of the fossils appeared to have nothing like them in the living world of to-day, but some analogous forms might yet be found, he thought, in still unexplored parts of the earth; and even if no living representatives should ever be discovered, many types of animals might have undergone transformation during the great changes which had affected the surface of the earth.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ He had no hesitation in affirming that, even if no shells had ever been found living in the sea, the internal structure of these fossils would demonstrate that they once formed parts of living animals.

.In spite of his clear realization of the vast store of potential energy residing within the highly heated interior of the earth, Leibnitz continued to regard volcanic action as due to the combustion of inflammable substances enclosed within the terrestrial crust, such as stone-coal, naphtha and sulphur.^ In spite of his clear realization of the vast store of potential energy residing within the highly heated interior of the earth, Leibnitz continued to regard volcanic action as due to the combustion of inflammable substances enclosed within the terrestrial crust, such as stone-coal, naphtha and sulphur.

^ He thought that the interior of our planet may " be a fluid mass, melted, but unchanged by the action of heat "; and, far from connecting volcanoes with the combustion of inflammable substances, as had been the prevalent belief for so many centuries, he looked upon them as a beneficent provision of " spiracles to the subterranean furnace , in order to prevent the unnecessary elevation of land and fatal effects of earthquakes."

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

.Appealing to a much wider public than Descartes or Leibnitz, and basing his speculations on a wider acquaintance with the organic and inorganic realms of nature, G. L. L. de Buffon (1707-1788) was undoubtedly one of the most influential forces that in Europe guided the growth of geological ideas during the 18th century.^ Appealing to a much wider public than Descartes or Leibnitz, and basing his speculations on a wider acquaintance with the organic and inorganic realms of nature, G. L. L. de Buffon (1707-1788) was undoubtedly one of the most influential forces that in Europe guided the growth of geological ideas during the 18th century.

^ The ideas of Descartes regarding planetary evolution were enlarged and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), whose teaching has largely influenced all subsequent speculation centuries that have elapsed since that event, the whole of the fossiliferous rocks might have been deposited.

^ The term " geology,"' descriptive of this branch of the investigation of nature, was not proposed until the last quarter of the 18th century by Jean Andre De Luc (1727-1817) and Horace Benedict De Saussure (1740-1749).

.He published in 1749 a Theory of the Earth, in which he adopted views similar to those of Descartes and Leibnitz as to planetary evolution; but though he realized the importance of fossils as records of former conditions of the earth's surface, he accounted for them by supposing that they had been deposited from a universal ocean, a large part of which had subsequently been engulfed into caverns in the interior of the globe.^ He published in 1749 a Theory of the Earth, in which he adopted views similar to those of Descartes and Leibnitz as to planetary evolution; but though he realized the importance of fossils as records of former conditions of the earth's surface, he accounted for them by supposing that they had been deposited from a universal ocean, a large part of which had subsequently been engulfed into caverns in the interior of the globe.

^ The ideas of Descartes regarding planetary evolution were enlarged and made more definite by Wilhelm Gottfried Leibnitz (1646-1716), whose teaching has largely influenced all subsequent speculation centuries that have elapsed since that event, the whole of the fossiliferous rocks might have been deposited.

^ In his great tract, the Protogaea (published in 1749, thirty-three years after his death), he traced the probable passage of our earth from an original condition of incandescent vapour into that of a smooth molten globe, which, by continuous cooling, acquired an external solid crust and rugose surface.

.Thirty years later, after having laboured with skill and enthusiasm in all branches of natural history, he published another work, his famous Epoques de la nature (1778), which is specially remarkable as the first attempt to deal with the history of the earth in a chronological manner, and to compute, on a basis of experiment, the antiquity of the several stages of this history.^ Thirty years later, after having laboured with skill and enthusiasm in all branches of natural history, he published another work, his famous Epoques de la nature (1778), which is specially remarkable as the first attempt to deal with the history of the earth in a chronological manner, and to compute, on a basis of experiment, the antiquity of the several stages of this history.

^ Of the former type were the works of Martin Lister (1638-1712) and Robert Plot ( Natural History of Oxfordshire , 1677).

^ Of modern English works, Sir A. Geikie's Text Book of Geology (4th ed., 1903) occupies the first place; the work of T. C. Chamberlin and R. D. Salisbury , Geology; Earth History (3 vols., 1905-1906), is especially valuable for American geology.

.His experiments were made with globes of cast iron, and could not have yielded results of any value for his purpose; but in so far as his calculations were not mere random guesses but had some kind of foundation on experiment, they deserve respectful recognition.^ His experiments were made with globes of cast iron , and could not have yielded results of any value for his purpose; but in so far as his calculations were not mere random guesses but had some kind of foundation on experiment, they deserve respectful recognition.

^ Hence for the purposes of the geologist the fossil remains of marine forms of life far surpass all others in value.

^ Again, banks of sea-shells in far inland districts would, in course of time, arrest the attention of the more intelligent and reflective observers, and raise in their minds some kind of surmise as to how such shells could ever have come there.

.He divided the history of our earth into six periods of unequal duration, the whole comprising a period of some 70,000 or 75,000 years.^ He divided the history of our earth into six periods of unequal duration, the whole comprising a period of some 70,000 or 75,000 years.

^ According to some investigators, it should be regarded as in large measure of meteoric origin, derived from the descent of rain into the earth, and its absorption by the molten magma in the interior.

^ They can be tested by an appeal to the crust of the earth, in which the geological history of our planet has been so fully recorded.

.He supposed that the stage of incandescence, before the globe had consolidated to the centre, lasted 2936 years, and that about 35,000 years elapsed before the surface had cooled sufficiently to be touched, and therefore to be capable of supporting living things.^ He supposed that the stage of incandescence, before the globe had consolidated to the centre, lasted 2936 years, and that about 35,000 years elapsed before the surface had cooled sufficiently to be touched, and therefore to be capable of supporting living things.

^ He thinks that it does not seem extravagant to suppose that Soo to 1000 million years may have elapsed since the birth of the moon."

^ The dunes most likely postdate the last high stand of Lake Manly, probably about 18,000 years ago.
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.Terrestrial animal life, however, was not introduced until 55,000 or 60,000 years after the beginning of the world or about 15,000 years before our time.^ Terrestrial animal life, however, was not introduced until 55,000 or 60,000 years after the beginning of the world or about 15,000 years before our time.

^ Looking into the future, he foresaw that, by continued refrigeration, our globe will eventually become colder than ice , and this fair face of nature, with its manifold varieties of plant and animal life, will perish after having existed for 132,000 years.

^ These light colored silt and sand deposits were probably laid down about 15,000 years ago and most likely represent a marsh or meadow (Klinger, R. E., 2007).
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.Looking into the future, he foresaw that, by continued refrigeration, our globe will eventually become colder than ice, and this fair face of nature, with its manifold varieties of plant and animal life, will perish after having existed for 132,000 years.^ Looking into the future, he foresaw that, by continued refrigeration, our globe will eventually become colder than ice , and this fair face of nature, with its manifold varieties of plant and animal life, will perish after having existed for 132,000 years.

^ By such long-continued attrition the rocks are worn down, portions of them of softer nature, or where the ice acts with especial vigour, are hollowed out into cavities which, on the disappearance of the ice, may be filled with water and become tarns or lakes.

^ Perhaps the most subtle of human influences are to be seen in the distribution of plant and animal life upon the globe.

.Buffon's conception of the operation of the geological agents did not become broader or more accurate in the interval between the appearance of his two treatises.^ Buffon's conception of the operation of the geological agents did not become broader or more accurate in the interval between the appearance of his two treatises.

^ The interval between the deposit of two successive laminae of shale may have been as long as, or even longer than, that required for the formation of one of the laminae.

^ Epigene Or Superficial Action It is on the surface of the globe, and by the operation of agents working there, that at present the chief amount of visible geological change is effected.

.He still continued to believe in the lowering of the ocean by subsidence into vast subterranean cavities, with a consequent emergence of land.^ He still continued to believe in the lowering of the ocean by subsidence into vast subterranean cavities, with a consequent emergence of land.

^ He thought that certain exhalations within the earth condense into oil, which, when_ in violent motion, enters into the subterranean cavities, where it passes into a kind of smoke .

^ It is manifest , however, that, whatever may have been the original composition of the oceans, they have for a vast section of geological time been constantly receiving mineral matter in solution from the land.

.He still looked on volcanoes as due to the burning of " pyritous and combustible stones," though he now called in the co-operation of electricity.^ He still looked on volcanoes as due to the burning of " pyritous and combustible stones," though he now called in the co-operation of electricity .

^ Still under the old misconception that volcanoes are due to the combustion of inflammable materials, which he thought might be set on fire by the spontaneous combustion of pyritous strata, he supposed that, by the sudden access of large bodies of water to these subterranean fires, vapour is produced in such quantity and with such force as to give rise to the shock.

.He calculated that the first volcanoes could not arise until some 50,000 years after the beginning of the world, by which time a sufficient extent of dense vegetation had been buried in the earth to supply them with fuel.^ He calculated that the first volcanoes could not arise until some 50,000 years after the beginning of the world, by which time a sufficient extent of dense vegetation had been buried in the earth to supply them with fuel.

^ Werner, following the old tradition, looked upon volcanoes as modern features in the history of the planet, which could not have come into existence until a sufficient amount of vegetation had been buried to furnish fuel for their maintenance.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.He appears to have had but an imperfect acquaintance with the literature of his own time.^ He appears to have had but an imperfect acquaintance with the literature of his own time.

.At least there can be little doubt that had he availed himself of the labours of his own countryman, Jean Etienne Guettard (1715-1786), of Giovanni Arduino (1714-1795) in Italy, and of Johann Gottlob Lehmann (d.^ At least there can be little doubt that had he availed himself of the labours of his own countryman, Jean Etienne Guettard (1715-1786), of Giovanni Arduino (1714-1795) in Italy, and of Johann Gottlob Lehmann (d.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

^ In Italy G. Arduino (1713-1795) classified the rocks in the north of the peninsula as Primitive, Secondary, Tertiary and Volcanic.

.1767) and George Christian Fiichsel (1722-1773) in Germany, he would have been able to give to his " epochs " a more definite succession of events and a greater correspondence with the facts of nature.^ George Christian Fiichsel (1722-1773) in Germany, he would have been able to give to his " epochs " a more definite succession of events and a greater correspondence with the facts of nature.

^ The weak game is allowed to live, which would otherwise be killed off and give more room for the healthy remainder.

^ It was needful, therefore, to find some explanation of the facts of nature, which would not run counter to the ecclesiastical system of the day.

.Among the writers of the 18th century, who formed philosophical conceptions of the system of processes by which the life of our earth as a habitable globe is carried on, a foremost place must be assigned to James Hutton (1726-1797).^ Among the writers of the 18th century, who formed philosophical conceptions of the system of processes by which the life of our earth as a habitable globe is carried on, a foremost place must be assigned to James Hutton (1726-1797).

^ One good result of the controversy, however, was to be seen in the large collections of these " formed stones" that were gathered together in the cabinets and museums of the 17th and 18th centuries.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.Educated for the medical profession, he studied at Edinburgh and at Paris, and took his doctor's degree at Leiden.^ Educated for the medical profession, he studied at Edinburgh and at Paris , and took his doctor's degree at Leiden .

.But having inherited a small landed property in Berwickshire, he took to agriculture, and after putting his land into excellent order, let his farm and betook himself to Edinburgh, there to gratify the scientific tastes which he had developed early in life.^ But having inherited a small landed property in Berwickshire , he took to agriculture , and after putting his land into excellent order, let his farm and betook himself to Edinburgh, there to gratify the scientific tastes which he had developed early in life.

^ Any such deep-sea formation, if raised into land, would supply but a meagre picture of the whole life of the sea.

.He had been more especially led to study minerals and rocks, and to meditate on the problems which they suggest as to the constitution and history of the earth.^ He had been more especially led to study minerals and rocks, and to meditate on the problems which they suggest as to the constitution and history of the earth.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ I-Ie published in 1669 a small tract, De solido intra solidum naturaliter contento, in which he developed the ideas he had formed of this history from an attentive study of the rocks.

.His journeys in Britain and on the continent of Europe had furnished him with material for reflection; and he had gradually evolved a system or theory in which all the scattered facts could be arranged so as to show their mutual dependence and their place in the orderly mechanism of the world.^ His journeys in Britain and on the continent of Europe had furnished him with material for reflection; and he had gradually evolved a system or theory in which all the scattered facts could be arranged so as to show their mutual dependence and their place in the orderly mechanism of the world.

^ Pangaea: According to some theories, a great proto-continent from which all present continents have broken off by the mechanism of sea-floor spreading and continental drift.
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^ If we were not aware from authentic records that central and northern Europe were covered with vast forests at the beginning of our era, how could we know this fact?

.He used to discuss his views with one or two of his friends, but refrained from publishing them to the world until, on the foundation of the Royal Society of Edinburgh, he communicated an outline of his doctrine to that learned body in 1785. Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations. Hutton's teaching has exercised a profound influence on modern geology.^ He used to discuss his views with one or two of his friends, but refrained from publishing them to the world until, on the foundation of the Royal Society of Edinburgh, he communicated an outline of his doctrine to that learned body in 1785.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

^ Hutton's teaching has exercised a profound influence on modern geology.

.This influence, however, has arisen less from his own writings than from the account of his doctrines given by his friend John Playfair in the classic work entitled Playfair.^ This influence, however, has arisen less from his own writings than from the account of his doctrines given by his friend John Playfair in the classic work entitled Playfair.

^ He approached the subject from an opposite and less philosophical point of view than that of Lamarck, coming to it with certain preconceived notions, which affected all his subsequent writings.

^ They were looked on as the champions of orthodoxy; and, on that account, they doubtless wielded much more influence than would have been gained by them from the force of their arguments.

.Illustrations of the Huttonian Theory,
published in 1802. Hutton wrote in so prolix and obscure a style as rather to repel than attract readers.^ Illustrations of the Huttonian Theory, published in 1802.

^ Hutton wrote in so prolix and obscure a style as rather to repel than attract readers.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

.Playfair, on the other hand, expressed himself in such clear and graceful language as to command general attention, and to gain wide acceptance for his master's views.^ Playfair, on the other hand, expressed himself in such clear and graceful language as to command general attention, and to gain wide acceptance for his master's views.

^ It is obvious, of course,; that such breaks, even though traceable over wide regions, were not general over the whole globe.

.Unlike the older cosmogonists, Hutton refrained from trying to explain the origin of things, and from speculations as to what might possibly have been the early history of our globe.^ Unlike the older cosmogonists, Hutton refrained from trying to explain the origin of things, and from speculations as to what might possibly have been the early history of our globe.

^ The early experiments of Sir James Hall, already noticed, formed the starting-point for numerous subsequent researches, which have elucidated many points in the origin and history of rocks.

^ Up to the present time no definite light has been thrown by physics on the origin and earliest condition of our globe.

.He determined from the outset to interpret the past by what can be seen to be the present order of nature; and he refused to admit the operation of causes which cannot be shown to be part of the actual terrestrial system.^ He determined from the outset to interpret the past by what can be seen to be the present order of nature; and he refused to admit the operation of causes which cannot be shown to be part of the actual terrestrial system.

^ It is true that we cannot hope to imitate those operations of nature which demand enormous pressures and excessively high temperatures combined with a long lapse of time.

^ It is supposed that the wholesale destruction of the woodlands formerly existing in countries bordering the Mediterranean has been in part the cause of the present desiccation of these districts.

.Like other observers who had preceded him, he recognized in the various rocks composing the dry land evidence of former geographical conditions very different from those which now prevail.^ Like other observers who had preceded him, he recognized in the various rocks composing the dry land evidence of former geographical conditions very different from those which now prevail.

^ The ripple lift upon the shore, the cracks formed by the sun's heat upon the muddy bottom of a dried-up pool , the very imprint of the drops of a passing rainshower, have all been accurately preserved, and yield their evidence as to geographical conditions often widely different from those which exist where such markings are now found.

^ As this branch of the science deals with the evidence furnished by fossil organic remains as to former geographical conditions, it early attracted observers who, in the superficial beds of marine shells found at some distance from the coast, saw proofs of the former submergence of the land under the sea.

.He saw that the vast majority of rocks consist of hardened sediments and must have been deposited in the sea.^ He saw that the vast majority of rocks consist of hardened sediments and must have been deposited in the sea.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Their materials have been laid down in laminae, layers and strata, or beds, pointing generally to the intermittent deposition of the sediments of which they consist.

.He could distinguish among them an older or Primary series, and a younger or Secondary series; and did not dispute the existence of a Tertiary series claimed by Peter Simon Pallas (1741-1811).^ He could distinguish among them an older or Primary series, and a younger or Secondary series; and did not dispute the existence of a Tertiary series claimed by Peter Simon Pallas (1741-1811).

^ But where the older series has been tilted up or visibly denuded before being overlain by the younger, the latter is termed unconformable.

^ He at first believed, as Murchison also did, that his rocks were all older than any part of the Silurian series.

.He believed that these various aqueous accumulations had been consolidated by subterranean heat, that the oldest and lowest rocks had suffered most from this action, that into these more deep-seated masses subsequent veins and larger bodies of molten matter were injected from below, and thus that what was originally loose detritus eventually became changed in such crystalline schists as are now found in mountain-chains.^ He believed that these various aqueous accumulations had been consolidated by subterranean heat, that the oldest and lowest rocks had suffered most from this action, that into these more deep-seated masses subsequent veins and larger bodies of molten matter were injected from below, and thus that what was originally loose detritus eventually became changed in such crystalline schists as are now found in mountain-chains.

^ The most important subsequent change in the classification of the Tertiary formations was made by Sir Charles Lye 11, who, conceiving in 1828 the idea of a classification of these rocks by reference to their relative proportions of living and extinct species of shells, established, in collaboration with G. P. Deshayes , the now universally accepted divisions Eocene , Miocene and Pliocene .

^ There is a natural tendency to see in a stupendous piece of scenery, such as a deep ravine, a range of hills, a line of precipice or a chain of mountains, evidence only of subterranean convulsion; and before the subject was taken up as a matter of strict scientific induction , an appeal to former cataclysms was considered a sufficient solution of the problems presented by such features of landscape.

.In the course of these terrestrial revolutions sedimentary strata, originally more or less nearly horizontal, have been pushed upward, dislocated, crumpled, placed on end, and even elevated to form ranges of lofty mountains.^ In the course of these terrestrial revolutions sedimentary strata, originally more or less nearly horizontal, have been pushed upward, dislocated, crumpled, placed on end, and even elevated to form ranges of lofty mountains.

^ John Michell (1760), in the paper on earthquakes already cited, showed that he had acquired a clear understanding of the order of succession among stratified formations, and perceived that to disturbances of the terrestrial crust must be ascribed the fact that the lower or older and more inclined strata form the mountains, while the younger and more horizontal strata are spread over the plains.

^ Each " formation " is distinguished by its own peculiar assemblage of organic remains, by means of which it can be followed and recognized, even amid the crumplings and dislocations of a disturbed region.

.Hutton looked upon these disturbances as due to the expansive power of subterranean heat; but he did not attempt to sketch the mechanism of the process, and he expressly declined to offer any conjecture as to how the land so elevated remains in that position.^ Hutton looked upon these disturbances as due to the expansive power of subterranean heat; but he did not attempt to sketch the mechanism of the process, and he expressly declined to offer any conjecture as to how the land so elevated remains in that position.

^ He thought that the interior of our planet may " be a fluid mass, melted, but unchanged by the action of heat "; and, far from connecting volcanoes with the combustion of inflammable substances, as had been the prevalent belief for so many centuries, he looked upon them as a beneficent provision of " spiracles to the subterranean furnace , in order to prevent the unnecessary elevation of land and fatal effects of earthquakes."

^ The reproductive action of the air arises partly from the effect of the chemical and mechanical disintegration involved in the process of " weathering," and partly from the transporting power of wind and of aerial currents.

He thought that the interior of our planet may " be a fluid mass, melted, but unchanged by the action of heat "; and, far from connecting volcanoes with the combustion of inflammable substances, as had been the prevalent belief for so many centuries, he looked upon them as a beneficent provision of " spiracles to the subterranean furnace, in order to prevent the unnecessary elevation of land and fatal effects of earthquakes." A distinguishing feature of the Huttonian philosophy is to be seen in the breadth of its conceptions regarding the geological operations continually in progress on the surface of the globe. .Hutton saw that the land is undergoing a ceaseless process of degradation, through the influence of the air, frost, rain, rivers and the sea, and that in course of time, if no countervailing agency should intervene, the whole of the dry land will be washed away into the sea.^ Hutton saw that the land is undergoing a ceaseless process of degradation, through the influence of the air, frost, rain , rivers and the sea, and that in course of time, if no countervailing agency should intervene, the whole of the dry land will be washed away into the sea.

^ From the time that any portion of the sea-floor appears above sea-level, it undergoes erosion by the various epigene agents.

^ It was cogently enforced by Hutton and Playfair, and independently by Lamarck, that no co-operation of underground agency is needed to produce such topography as may be seen in a great part of the world, but that if a tract of sea-floor were upraised into a wide plain, the fall of rain and the circulation of water over its surface would in the end carve out such a system of hills and valleys as may be seen on the dry land now.

.But he also perceived that this universal erosion is not everywhere carried on at the same rate; that it is specially active along the channels of torrents and rivers, and that, owing to this difference, these channels are gradually deepened and widened, until the complicated valley-system of a country is carved out.^ But he also perceived that this universal erosion is not everywhere carried on at the same rate; that it is specially active along the channels of torrents and rivers, and that, owing to this difference, these channels are gradually deepened and widened, until the complicated valley-system of a country is carved out.

^ No sooner, however, are they placed in that position than they are attacked by running water, and begin to be hollowed out into systems of valleys.

^ Valleys have in general been hollowed out by the greater erosive action of running water along the channels of drainage.

.He recognized that the detritus worn away from the land must be spread out over the floor of the sea, so as to form there strata similar to those that compose most of the dry land.^ He recognized that the detritus worn away from the land must be spread out over the floor of the sea, so as to form there strata similar to those that compose most of the dry land.

^ Pangaea: According to some theories, a great proto-continent from which all present continents have broken off by the mechanism of sea-floor spreading and continental drift.
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^ While the level of the land remains stationary, there can be but little effective entombment of marine organisms in littoral deposits; for only a limited accumulation of sediment will be formed until subsidence of the sea-floor takes place.

.As he could detect in the structure of land convincing evidence that former sea floors had been elevated to form the continents and islands of to-day, he could look forward to future ages, when the same subterranean agency which had raised up the present land would again be employed to uplift the bed of the existing ocean, thus to renew the surface of our earth as a habitable globe, and to start a fresh cycle of erosion and deposition.^ As he could detect in the structure of land convincing evidence that former sea floors had been elevated to form the continents and islands of to-day, he could look forward to future ages, when the same subterranean agency which had raised up the present land would again be employed to uplift the bed of the existing ocean, thus to renew the surface of our earth as a habitable globe, and to start a fresh cycle of erosion and deposition.

^ Looking into the future, he foresaw that, by continued refrigeration, our globe will eventually become colder than ice , and this fair face of nature, with its manifold varieties of plant and animal life, will perish after having existed for 132,000 years.

^ A study of the land-surfaces and sea-floors of the present time shows that there are so many chances against the conservation of the remains of either terrestrial or marine animals and plants that if, as is probable, the same conditions existed in former geological periods, we should regard the occurrence of organic remains among the stratified formations of the earth's crust as generally the result of various fortunate accidents.

.Though Hutton was not unaware that organic remains abound in many of the stratified rocks, he left them out of consideration in the elaboration of his theory.^ Though Hutton was not unaware that organic remains abound in many of the stratified rocks, he left them out of consideration in the elaboration of his theory.

^ To the geologist the presence of mineral solutions in sea-water is a fact of much importance, for it explains the origin of a considerable part of the stratified rocks of the earth's crust.

^ An important feature in the cosmogony of Leibnitz is the prominent place which he assigned to organic remains in the stratified rocks of the crust.

It was otherwise with Lamarck. one of his French contemporaries, the illustrious J. B.
.Lamarck (1744-1829), who, after having attained great eminence as a botanist, turned to zoology when he was nearly fifty years of age, and before long rose to even greater distinction in that department of science.^ Lamarck (1744-1829), who, after having attained great eminence as a botanist, turned to zoology when he was nearly fifty years of age, and before long rose to even greater distinction in that department of science.

^ In most great chains, however, the rocks have been so intensely crumpled, and even inverted, that much labour may be required before their true relations can be determined.

^ But on the west side of Sweden, fronting the Skager Rak, the coast, between the years 1820 and 1870, rose 30 centimetres, which is at the rate of 60 centimetres, or nearly 2 ft.

.His share in the classification and description of the mollusca and in founding invertebrate palaeontology, his theory of organic evolution and his philosophical treatment of many biological questions have been tardily recognized, but his contributions to geology have been less generally acknowledged.^ His share in the classification and description of the mollusca and in founding invertebrate palaeontology , his theory of organic evolution and his philosophical treatment of many biological questions have been tardily recognized, but his contributions to geology have been less generally acknowledged.

^ The mollusca of the Tertiary deposits of the Paris basin became, in the hands of Lamarck, the basis on which invertebrate palaeontology wasfounded.

^ Though Hutton was not unaware that organic remains abound in many of the stratified rocks, he left them out of consideration in the elaboration of his theory.

.When he accepted the " professorship of zoology; of insects, of worms and of microscopic animals " at the Museum of Natural History, Paris, in 1793, he at once entered with characteristic ardour and capacity into the new field of research then opened to him.^ When he accepted the " professorship of zoology; of insects, of worms and of microscopic animals " at the Museum of Natural History, Paris, in 1793, he at once entered with characteristic ardour and capacity into the new field of research then opened to him.

^ Petrology entered upon a new and wider field of investigation.

^ These interruptions serve as natural divisions in the chronicle, and enable the geologist to arrange his history into periods.

.In dealing with the mollusca he considered not merely the living but also the extinct forms, especially the abundant, varied and well-preserved genera and species furnished by the Tertiary deposits of the Paris basin, of which he published descriptions and plates that proved of essential service in the stratigraphical work of Cuvier and Alexandre Brongniart (1770-1847).^ As Death Valley has dropped over the past 20 million years, various basins have formed and filled with sediment.
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.His labours among these relics of ancient seas and lakes led him to ponder over the past history of the globe, and as he was seldom dilatory in making known the opinions he had formed, he communicated some of his conclusions to the National Institute in 1799. These, including a further elaboration of his views, he published in 1802 in a small volume entitled Hydrogeologie. This treatise, though it did not reach a second edition and has never been reprinted, deserves an honourable place in geological literature.^ His labours among these relics of ancient seas and lakes led him to ponder over the past history of the globe, and as he was seldom dilatory in making known the opinions he had formed, he communicated some of his conclusions to the National Institute in 1799.

^ These, including a further elaboration of his views, he published in 1802 in a small volume entitled Hydrogeologie.

^ This treatise, though it did not reach a second edition and has never been reprinted, deserves an honourable place in geological literature.

.Its object, the author states, was to present some important and novel considerations, which he thought should form the basis of a true theory of the earth.^ Its object, the author states, was to present some important and novel considerations, which he thought should form the basis of a true theory of the earth.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

^ The cosmogonists and framers of Theories of the Earth were succeeded by other schools of thought.

.He entirely agreed with the doctrine of the subaerial degradation of the land and the erosion of valleys by running water.^ He entirely agreed with the doctrine of the subaerial degradation of the land and the erosion of valleys by running water.

^ No sooner, however, are they placed in that position than they are attacked by running water, and begin to be hollowed out into systems of valleys.

^ Valleys have in general been hollowed out by the greater erosive action of running water along the channels of drainage.

Not even Playfair could have stated this doctrine more emphatically, and it is worthy of notice that Playfair's Illustrations of the Huttonian Theory appeared in the same year with Lamarck's book. .The French naturalist, however, carried his conclusions so far as to take no account of any great movements of the terrestrial crust, which might have produced or modified the main physical features of the surface of the globe.^ The French naturalist, however, carried his conclusions so far as to take no account of any great movements of the terrestrial crust, which might have produced or modified the main physical features of the surface of the globe.

^ Take, for example, the proofs of gigantic plication, fracture and displacement within the terrestrial crust.

^ From time to time the surface suffers calamitous devastation from earthquakes, when portions of the crust under great strain suddenly give way.

.He thought that all mountains, except such as were thrown up by volcanic agency or local accidents, have been cut out of plains, the original surfaces of which are indicated by the crests and summits of these elevations.^ He thought that all mountains, except such as were thrown up by volcanic agency or local accidents, have been cut out of plains, the original surfaces of which are indicated by the crests and summits of these elevations.

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

^ Up to the present time no definite light has been thrown by physics on the origin and earliest condition of our globe.

.Lamarck, in reflecting upon the wide diffusion of fossil shells and the great height above the sea at which they are found, conceived the extraordinary idea that the ocean basin has been scoured out by the sea, and that, by an impulse communicated to the waters through the influence chiefly of the moon, the sea is slowly eating away the eastern margins of the continents, and throwing up detritus on their western coasts, and is thus gradually shifting its basin round the globe.^ Lamarck, in reflecting upon the wide diffusion of fossil shells and the great height above the sea at which they are found, conceived the extraordinary idea that the ocean basin has been scoured out by the sea, and that, by an impulse communicated to the waters through the influence chiefly of the moon , the sea is slowly eating away the eastern margins of the continents, and throwing up detritus on their western coasts, and is thus gradually shifting its basin round the globe.

^ Girolamo Fracastorio (1483-1553) claimed that the shells could never have been left by the Flood, which was a mere temporary inundation, but that they proved the mountains, in which they occur, to have been successively uplifted out of the sea.

^ A similar conclusion was drawn by Xanthus the Lydian (464 B.C.) from shells like scallops and cockles, which were found far from the sea in Armenia and Lower Phrygia .

.He would not admit the operation of cataclysms; but insisted as strongly as Hutton on the continuity of natural processes, and on the necessity of explaining former changes of the earth's surface by causes which can still be seen to be in operation.^ He would not admit the operation of cataclysms; but insisted as strongly as Hutton on the continuity of natural processes, and on the necessity of explaining former changes of the earth's surface by causes which can still be seen to be in operation.

^ While, however, the present condition of things is thus employed, we must obviously be on our guard against the danger of unconsciously assuming that the phase of nature's operations which we now witness has been the same in all past time, that geological changes have always or generally taken place in former ages in the manner and on the scale which we behold to-day, and that at the present time all the great geological processes, which have produced changes in the past eras of the earth's history, are still existent and active.

^ While Lamarck was by instinct an evolutionist, who sought to trace in the history of the past the operation of the same natural processes as are still at work, Cuvier, on the other hand, was a catastrophist, who invoked a succession of vast cataclysms to account for the interruptions in the continuity of the geological record.

.As might be anticipated from his previous studies, he brought living things and their remains into the forefront of his theory of the earth.^ As might be anticipated from his previous studies, he brought living things and their remains into the forefront of his theory of the earth.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

^ One of the distinguishing features of Hutton's Theory of the Earth consisted in his protest that it is no part of the province of geology to discuss the origin of things.

.He looked upon fossils as one of the chief means of comprehending the revolutions which the surface of the earth has undergone; and in his little volume he again and again dwells on the vast antiquity to which these revolutions bear witness.^ He looked upon fossils as one of the chief means of comprehending the revolutions which the surface of the earth has undergone; and in his little volume he again and again dwells on the vast antiquity to which these revolutions bear witness.

^ In the former case we have to deal with the interior of the earth, and its reaction upon the surface; in the latter, we deal with the surface of the earth and to some extent with its reaction on the interior.

^ At this location and further up the hill, one can get a good look at these rocks even if they are deformed and metamorphosed a bit.
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.He acutely argues, from the condition of fossil shells, that they must have lived and died where their remains are now found.^ He acutely argues, from the condition of fossil shells, that they must have lived and died where their remains are now found.

^ More especially noteworthy was a monograph by him which appeared in 1765 bearing the title " On the accidents that have befallen Fossil Shells compared with those which are found to happen to shells now living in the Sea."

^ The most ancient crinoids, sponges , crustaceans, arachnids and molluscs were as delicately constructed as those of to-day, and their remains are often found in such perfect preservation as to show that neither during their lifetime nor after their death were they subject to any greater violence of the elements than their living representatives now experience.

.In the last part of his treatise Lamarck advances some peculiar opinions in physics and chemistry, which he had broached eighteen years before, but which had met with no acceptance among the scientific men of his time.^ In the last part of his treatise Lamarck advances some peculiar opinions in physics and chemistry , which he had broached eighteen years before, but which had met with no acceptance among the scientific men of his time.

^ Terrestrial animal life, however, was not introduced until 55,000 or 60,000 years after the beginning of the world or about 15,000 years before our time.

^ But there are some serious physical difficulties in the way of the acceptance of the nebular hypothesis.

.He believed that the tendency of all compound substances is to decay, and thereby to be resolved into their component constituents.^ He believed that the tendency of all compound substances is to decay, and thereby to be resolved into their component constituents.

^ The present outer envelope of air may be considered to be the surviving relic of this condition, after all the other constituents have been incorporated into the hydrosphere and lithosphere.

.Yet he saw that the visible crust of the earth consists almost wholly of compound bodies.^ Yet he saw that the visible crust of the earth consists almost wholly of compound bodies.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ These bodies were found to consist of elements all of which had been recognized as entering into the constitution of the earth.

.He therefore set himself to solve the problem thus presented.^ He therefore set himself to solve the problem thus presented.

.Perceiving that the biological action of living organisms is constantly forming combinations of matter, which would never have otherwise come into existence, he proceeded to draw the extraordinary conclusion that the action of plant and animal life (the Pouvoir de la vie) upon the inorganic world is so universal and so potent, that the rocks and minerals which form the outer part of the earth's crust are all, without exception, the result of the operations of once living bodies.^ Perceiving that the biological action of living organisms is constantly forming combinations of matter, which would never have otherwise come into existence, he proceeded to draw the extraordinary conclusion that the action of plant and animal life (the Pouvoir de la vie ) upon the inorganic world is so universal and so potent, that the rocks and minerals which form the outer part of the earth's crust are all, without exception, the result of the operations of once living bodies.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ I-Ie published in 1669 a small tract, De solido intra solidum naturaliter contento, in which he developed the ideas he had formed of this history from an attentive study of the rocks.

.Though this sweeping deduction must be allowed to detract from the value of Lamarck's work, there can be no doubt that he realized, more fully than any one had done before him, the efficacy of plants and animals as agents of geological change.^ Though this sweeping deduction must be allowed to detract from the value of Lamarck's work, there can be no doubt that he realized, more fully than any one had done before him, the efficacy of plants and animals as agents of geological change.

^ No more striking illustration of this feature can be found than that supplied by the Alps, nor one where the geotectonic structures have been so fully studied in detail.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

.The last notable contributor to the cosmological literature of geology was another illustrious Frenchman, the comparative ana.^ The last notable contributor to the cosmological literature of geology was another illustrious Frenchman, the comparative ana .

tomist .Cuvier (1769-1832).^ Cuvier (1769-1832).

.He was contemporary with Cav Lamarck, but of a very different type of mind.^ He was contemporary with Cav Lamarck, but of a very different type of mind.

.The brilliance of his speculations, and the charm with which he expounded them, early gained for him a prominent place in the society of Paris.^ The brilliance of his speculations, and the charm with which he expounded them, early gained for him a prominent place in the society of Paris.

.He too was drawn by his zoological studies to investigate fossil organic remains, and to consider the former conditions of the earth's surface, of which they are memorials.^ He too was drawn by his zoological studies to investigate fossil organic remains, and to consider the former conditions of the earth's surface, of which they are memorials.

^ A study of the land-surfaces and sea-floors of the present time shows that there are so many chances against the conservation of the remains of either terrestrial or marine animals and plants that if, as is probable, the same conditions existed in former geological periods, we should regard the occurrence of organic remains among the stratified formations of the earth's crust as generally the result of various fortunate accidents.

^ It may be said that the absence of such proof ought not to invalidate the assertion until a far wider area of the earth's surface has been geologically studied.

.It was among the vertebrate organisms of the Paris basin that he found his chief material, and from them that he prepared the memoirs which led to him being regarded as the founder of vertebrate palaeontology.^ It was among the vertebrate organisms of the Paris basin that he found his chief material, and from them that he prepared the memoirs which led to him being regarded as the founder of vertebrate palaeontology.

^ On no tenable hypothesis can these be regarded as the first organisms that came into being on our planet.

^ The mollusca of the Tertiary deposits of the Paris basin became, in the hands of Lamarck, the basis on which invertebrate palaeontology wasfounded.

.But beyond their biological interest, they awakened in him a keen desire to ascertain the character and sequence of the geographical revolutions to which they bear witness.^ But beyond their biological interest, they awakened in him a keen desire to ascertain the character and sequence of the geographical revolutions to which they bear witness.

^ To him they were not only of deep interest as monuments of former types of existence, but they had an especial value as records of the changes which the country had undergone from sea to land and from land to sea.

^ This philosopher had been much interested in the accounts given him by survivors and witnesses of the earthquake which convulsed the district of Naples in February A.D. 63.

.He approached the subject from an opposite and less philosophical point of view than that of Lamarck, coming to it with certain preconceived notions, which affected all his subsequent writings.^ He approached the subject from an opposite and less philosophical point of view than that of Lamarck, coming to it with certain preconceived notions, which affected all his subsequent writings.

^ Subsequently Induced Structures After their accumulation, whether as stratified or eruptive masses, all kinds of rocks have been subject to various changes, and have acquired in consequence a variety of superinduced structures.

^ In a celebrated passage in his Metamorphoses, Ovid puts into the mouth of the philosopher Pythagoras an account of what was probably regarded as the Pythagorean view of the subject in the Augustan age.

.While Lamarck was by instinct an evolutionist, who sought to trace in the history of the past the operation of the same natural processes as are still at work, Cuvier, on the other hand, was a catastrophist, who invoked a succession of vast cataclysms to account for the interruptions in the continuity of the geological record.^ While Lamarck was by instinct an evolutionist, who sought to trace in the history of the past the operation of the same natural processes as are still at work, Cuvier, on the other hand, was a catastrophist, who invoked a succession of vast cataclysms to account for the interruptions in the continuity of the geological record.

^ Of the former type were the works of Martin Lister (1638-1712) and Robert Plot ( Natural History of Oxfordshire , 1677).

^ The examples of this process brought to light in Colorado, Wyoming , Nevada and the other western regions by Newberry, King, Hayden, Powell and other explorers, are among the most striking monuments of geological operations in the world.

.In a preliminary Discourse prefixed to his Recherches sur les ossemens fossiles (1821) Cuvier gave an outline of what he conceived to have been the past history of our globe, so far as he had been able to comprehend it from his investigations of the Tertiary formations of France.^ In a preliminary Discourse prefixed to his Recherches sur les ossemens fossiles (1821) Cuvier gave an outline of what he conceived to have been the past history of our globe, so far as he had been able to comprehend it from his investigations of the Tertiary formations of France.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

^ From the key which his researches supplied, it was possible to recognize in other countries the same order of formations and the same sequence of fossils, so that, in the course of a few years, representatives of the Silurian system were found far and wide over the globe.

.He believed that in that history evidence can be recognized of the occurrence of many sudden and disastrous revolutions, which, to judge from their effects on the animal life of the time, must have exceeded in violence anything we can conceive at the present day, and must have been brought about by other agencies than those which are now in operation.^ He believed that in that history evidence can be recognized of the occurrence of many sudden and disastrous revolutions, which, to judge from their effects on the animal life of the time, must have exceeded in violence anything we can conceive at the present day, and must have been brought about by other agencies than those which are now in operation.

^ But Professor Darwin, in the address just cited, uttered the memorable warning: " At present our knowledge of a definite limit to geological time has so little precision that we should do wrong summarily to reject theories which appear to demand longer periods of time than those which now appear allowable."

^ To what extent superficial changes of this kind have operated in geological history remains an unsolved problem, but their probable occurrence in the past has to be recognized as one of the factors that must be considered in tracing the revolutions of the earth's surface.

.Yet, in spite of these catastrophes, he saw that there has been an upward progress in the animal forms inhabiting the globe, until the series ended in the advent of man.^ Yet, in spite of these catastrophes, he saw that there has been an upward progress in the animal forms inhabiting the globe, until the series ended in the advent of man.

^ It teaches that there has been a progressive development of the inhabitants, as well as one of the globe on which they have dwelt; that each successive period in the earth's history, since the introduction of living things, has been marked by characteristic types of the animal and vegetable kingdoms; and that, however imperfectly the remains of these organisms have been preserved or may be deciphered, materials exist for a history of life upon the planet.

^ It is thus manifest that there must have been from time to time during the history of our globe upward movements of the crust, whereby the balance between land and sea was redressed.

.He could not, however, find any evidence that one species has been developed from another, for in that case there should have been traces of intermediate forms among the stratified formations, where he affirmed that they had never been found.^ He could not, however, find any evidence that one species has been developed from another, for in that case there should have been traces of intermediate forms among the stratified formations, where he affirmed that they had never been found.

^ They were inclined to disbelieve that the stratified formations of the earth's crust furnish conclusive evidence of a gradual progression, from simple types of life in the oldest strata to the most highly developed forms in the youngest; and saw no reason why remains of the higher vertebrates should not be met with among the Palaeozoic formations.

^ There can be little doubt that such has, in fact, been the history of the main mass of stratified formations in the earth's crust.

.A prominent position in the Discourse is given to a strenuous argument to disprove the alleged antiquity of some nations, and to show that the last great catastrophe occurred not more than some 5000 or 6000 years ago.^ A prominent position in the Discourse is given to a strenuous argument to disprove the alleged antiquity of some nations, and to show that the last great catastrophe occurred not more than some 5000 or 6000 years ago.

^ He insists that the time " was more than 20 and less than 40 millions of years and probably much nearer 20 than 40."

^ But we cannot assume it to be much less, and it may possibly have been much more, than the ioo millions of years which Lord Kelvin was at one time willing to concede.'

.Cuvier thus linked himself with those who in previous generations had contended for the efficacy of the Deluge.^ Cuvier thus linked himself with those who in previous generations had contended for the efficacy of the Deluge.

.But his researches among fossil animals had given him a far wider outlook into the geological past, and had opened up to him a succession of deeply interesting problems in the history of life upon the earth, which, though he had not himself material for their solution, he could foresee would be cleared up in the future.^ An inquiry into the materials of the earth's substance.

^ But his researches among fossil animals had given him a far wider outlook into the geological past, and had opened up to him a succession of deeply interesting problems in the history of life upon the earth, which, though he had not himself material for their solution, he could foresee would be cleared up in the future.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

Gradual Shaping of Geology into a Distinct Branch of Science

.It will be seen from the foregoing historical sketch that it was only after the lapse of long centuries, and from the labours of many successive generations of observers and writers, that what we now know as the science of geology came to be recognized as a distinct department of natural knowledge, founded upon careful and extended study of the structure of the earth, and upon observation of the natural processes, which are now at work in changing the earth's surface.^ It will be seen from the foregoing historical sketch that it was only after the lapse of long centuries, and from the labours of many successive generations of observers and writers, that what we now know as the science of geology came to be recognized as a distinct department of natural knowledge, founded upon careful and extended study of the structure of the earth, and upon observation of the natural processes, which are now at work in changing the earth's surface.

^ Eleven years later the observation was confirmed and greatly extended by Nicholas Desmarest (1725-1815), who, during a long course of years, worked out and mapped the complicated volcanic records of that interesting region, and demonstrated to all who were willing impartially to examine the evidence the true volcanic nature of basalt.

^ Especially necessary is a tolerably wide knowledge of the processes now at work in changing the surface of the earth, and of at least those forms of plant and animal life whose remains are apt to be preserved in geological deposits, or which in their structure and habitat enable us to realize what their forerunners were.

.The term " geology,"' descriptive of this branch of the investigation of nature, was not proposed until the last quarter of the 18th century by Jean Andre De Luc (1727-1817) and Horace Benedict De Saussure (1740-1749).^ The term " geology,"' descriptive of this branch of the investigation of nature, was not proposed until the last quarter of the 18th century by Jean Andre De Luc (1727-1817) and Horace Benedict De Saussure (1740-1749).

^ But their varieties of composition and origin did not become the subject of serious study until after Linnaeus and J. G. Wallerius in the 18th century had made a beginning.

^ In considering this branch of inquiry, we are not involved in a preliminary difficulty regarding the very nature of the agencies as is the case in the investigation of plutonic action.

.But the science was then in a markedly half-formed condition, theoretical speculation still in large part supplying the place of deductions from a detailed examination of actual fact.^ But the science was then in a markedly half-formed condition, theoretical speculation still in large part supplying the place of deductions from a detailed examination of actual fact.

^ The oxygen, which now forms fully a half of the outer crust of the earth, was doubtless originally, whether free or in combination, part of the atmosphere.

^ The circulation of water from the atmosphere to the land, from the land to the sea, and again from the sea to the land, forms the great geological process whereby the habitable condition of the planet is maintained and the surface of the land is sculptured (Part IV.).

In 1807 a few enterprising spirits founded the Geological Society of London for the special purpose of counteracting the prevalent tendency and confining their intention " to investigate the mineral structure of the earth." The cosmogonists and framers of Theories of the Earth were succeeded by other schools of thought. .The Catastrophists saw in the composition of the crust of the earth distinct evidence that the forces of nature were once much more stupendous in their operation than they now are, and that they had from time to time devastated the earth's surface; extirpating the races of plants and animals, and preparing the ground for new creations of organized life.^ The Catastrophists saw in the composition of the crust of the earth distinct evidence that the forces of nature were once much more stupendous in their operation than they now are, and that they had from time to time devastated the earth's surface; extirpating the races of plants and animals, and preparing the ground for new creations of organized life.

^ Cautiously at first, for fear of offending orthodox opinions, but afterwards more boldly, he proclaimed his conviction that those objects had once been part of living animals, and that they threw light on some of the past history of the earth.

^ Pointing to the whole body of evidence from inorganic and organic nature, they maintain that the history of our planet has been one of continual and unbroken development from the earliest cosmical beginnings down to the present time, and that the crust of the earth contains an abundant, though incomplete, record of the successive stages through which the plant and animal 1 In De Luc's Lettres physiques et morales sur les montagnes (1778), the word " cosmology " is used for our science, the author stating that " geology " is more appropriate, but it " was not a word in use."

.Then came the Uniformitarians, who, pushing the doctrines of Hutton to an extreme which he did not propose, saw no evidence that the activity of the various geological causes has ever seriously differed from what it is at present.^ Then came the Uniformitarians, who, pushing the doctrines of Hutton to an extreme which he did not propose, saw no evidence that the activity of the various geological causes has ever seriously differed from what it is at present.

^ There is no evidence that any portion of the present land ever lay under the deeper parts of the ocean.

^ Like other observers who had preceded him, he recognized in the various rocks composing the dry land evidence of former geographical conditions very different from those which now prevail.

.They were inclined to disbelieve that the stratified formations of the earth's crust furnish conclusive evidence of a gradual progression, from simple types of life in the oldest strata to the most highly developed forms in the youngest; and saw no reason why remains of the higher vertebrates should not be met with among the Palaeozoic formations.^ They were inclined to disbelieve that the stratified formations of the earth's crust furnish conclusive evidence of a gradual progression, from simple types of life in the oldest strata to the most highly developed forms in the youngest; and saw no reason why remains of the higher vertebrates should not be met with among the Palaeozoic formations.

^ It teaches that there has been a progressive development of the inhabitants, as well as one of the globe on which they have dwelt; that each successive period in the earth's history, since the introduction of living things, has been marked by characteristic types of the animal and vegetable kingdoms; and that, however imperfectly the remains of these organisms have been preserved or may be deciphered, materials exist for a history of life upon the planet.

^ He could not, however, find any evidence that one species has been developed from another, for in that case there should have been traces of intermediate forms among the stratified formations, where he affirmed that they had never been found.

.Sir Charles Lyell (1797-1875) was the great leader of this school.^ Sir Charles Lyell (1797-1875) was the great leader of this school.

^ General treatises: Sir Charles Lyell's Principles of Geology is a classic.

.His admirably clear and philosophical presentations of geological facts which, with unwearied industry, he collected from the writings of observers in all parts of the world, impressed his views upon the whole English-speaking world, and gave to geological science a coherence and interest which largely accelerated its progress.^ His admirably clear and philosophical presentations of geological facts which, with unwearied industry, he collected from the writings of observers in all parts of the world, impressed his views upon the whole English-speaking world, and gave to geological science a coherence and interest which largely accelerated its progress.

^ Possessed of great enthusiasm for his subject, clear, methodical and eloquent in his exposition of it, he soon drew around him men from all parts of the world, who repaired to study under the great oracle of what he called geognosy (Gr.

^ As this gaseous envelope encircles the whole globe it is the most universally present and active of all the agents of geological change.

In his later years, however, he frankly accepted the views of Darwin in regard to the progressive character of the geological record.
.The youngest of the schools of geological thought is that of the Evolutionists.^ The youngest of the schools of geological thought is that of the Evolutionists.

.Pointing to the whole body of evidence from inorganic and organic nature, they maintain that the history of our planet has been one of continual and unbroken development from the earliest cosmical beginnings down to the present time, and that the crust of the earth contains an abundant, though incomplete, record of the successive stages through which the plant and animal 1 In De Luc's Lettres physiques et morales sur les montagnes (1778), the word " cosmology " is used for our science, the author stating that " geology " is more appropriate, but it " was not a word in use."^ They have been deposited one over another in successive strata from a remote period in the development of the globe down to the present time.

^ They can be tested by an appeal to the crust of the earth, in which the geological history of our planet has been so fully recorded.

^ Pointing to the whole body of evidence from inorganic and organic nature, they maintain that the history of our planet has been one of continual and unbroken development from the earliest cosmical beginnings down to the present time, and that the crust of the earth contains an abundant, though incomplete, record of the successive stages through which the plant and animal 1 In De Luc's Lettres physiques et morales sur les montagnes (1778), the word " cosmology " is used for our science, the author stating that " geology " is more appropriate, but it " was not a word in use."

.In a completed edition, published in 1779, the same statement is made, but " geology " occurs in the text; in the same year De Saussure used the word without any explanation, as if it were well known.^ In a completed edition, published in 1779, the same statement is made, but " geology " occurs in the text; in the same year De Saussure used the word without any explanation, as if it were well known.

^ Geology: This very well known graben (down-dropped fault block) is about ¼ mile wide and about four miles long.
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^ Stratigraphical geology thus gathers up the sum of all that is made known by the other departments of the science, and makes it subservient to the interpretation of the geological history of the earth.

kingdoms have reached their existing organization. .The publication of Darwin's Origin of Species in 1859, in which evolution was made the key to the history of the animal and vegetable kingdoms, produced an extraordinary revolution in geological opinion.^ The publication of Darwin's Origin of Species in 1859, in which evolution was made the key to the history of the animal and vegetable kingdoms, produced an extraordinary revolution in geological opinion.

^ Geologists appear to have reluctantly brought themselves to believe that perhaps, after all, ioo millions of years might suffice for the evolution of geological history.

^ Stratigraphical geology thus gathers up the sum of all that is made known by the other departments of the science, and makes it subservient to the interpretation of the geological history of the earth.

.The older schools of thought rapidly died out, and evolution became the recognized creed of geologists all over the world.^ The older schools of thought rapidly died out, and evolution became the recognized creed of geologists all over the world.

^ Geologists appear to have reluctantly brought themselves to believe that perhaps, after all, ioo millions of years might suffice for the evolution of geological history.

^ He thought he could perceive the records of six successive phases in the evolution of the framework of that country, and was inclined to believe that a similar chronological sequence would be found all over the world.

Development of Opinion regarding Igneous Rocks

.So long as the idea prevailed that volcanoes are caused by the combustion of inflammable substances underground, there could be no rational conception of volcanic action and its products.^ So long as the idea prevailed that volcanoes are caused by the combustion of inflammable substances underground, there could be no rational conception of volcanic action and its products.

^ But where a volcano has appeared by itself, in a region previously exempt from volcanic action, the existence of a contributing fissure cannot be so confidently presumed.

^ These crude conceptions of the nature of volcanic action, and the cause of earthquakes, continued to prevail for many centuries.

.Even so late as the middle of the 18th century, as above remarked, such a good observer as Lazzaro Moro drew so little distinction between volcanic and other rocks that he could believe the fossiliferous formations to have been mainly formed of materials ejected from eruptive vents.^ Even so late as the middle of the 18th century, as above remarked, such a good observer as Lazzaro Moro drew so little distinction between volcanic and other rocks that he could believe the fossiliferous formations to have been mainly formed of materials ejected from eruptive vents.

^ There was likewise Lazzaro Moro (1687-1740), who did good service against the diluvialists, but the fundamental feature of his system of nature lay in the preponderant part which, unaware of the great difference between volcanic materials and ordinary sediment, he assigned to volcanic action in the production of the sedimentary rocks of the earth's crust.

^ One good result of the controversy, however, was to be seen in the large collections of these " formed stones" that were gathered together in the cabinets and museums of the 17th and 18th centuries.

.After his time the notion continued to prevail that all the rocks which form the dry land were laid down under water.^ After his time the notion continued to prevail that all the rocks which form the dry land were laid down under water.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Many rocks liable to be saturated with rain and rapidly dried under a warm sun are apt to disintegrate at the surface with comparative rapidity.

.Even streams of lava, which were seen to flow from an active crater, were regarded only as portions of sedimentary or other rocks, which had been melted by the fervent heat of the burning inflammable materials that had been kindled underground.^ By interfering with or even diverting the flow of streams.

^ Even streams of lava , which were seen to flow from an active crater, were regarded only as portions of sedimentary or other rocks, which had been melted by the fervent heat of the burning inflammable materials that had been kindled underground.

^ These materials arise either from the explosion of lava by the sudden expansion of the dissolved vapours and gases, as the molten rock rises to the surface, or from the breaking up and expulsion of portions of the walls of the vent, or of the lava, which happens to have solidified within these walls.

.In spite of the speculations of Descartes and Leibnitz, it was not yet generally comprehended that there exists beneath the terrestrial crust a molten magma, which, from time to time, has been injected into that crust, and has pierced through it, so as to escape at the surface with all the energy of an active volcano.^ In spite of the speculations of Descartes and Leibnitz, it was not yet generally comprehended that there exists beneath the terrestrial crust a molten magma, which, from time to time, has been injected into that crust, and has pierced through it, so as to escape at the surface with all the energy of an active volcano.

^ But it has been dogmatically affirmed that because terrestrial energy has been diminishing therefore all kinds of geological work must have been more vigorously and more rapidly carried on in former times than now; that there were far more abundant and more stupendous volcanoes, more frequent and more destructive earthquakes, more gigantic upheavals and subsidences, more powerful oceanic waves and tides, more violent atmospheric disturbances with heavier rainfall and more active denudation.

^ A study of the land-surfaces and sea-floors of the present time shows that there are so many chances against the conservation of the remains of either terrestrial or marine animals and plants that if, as is probable, the same conditions existed in former geological periods, we should regard the occurrence of organic remains among the stratified formations of the earth's crust as generally the result of various fortunate accidents.

.What we now recognize to be memorials of these former injections and propulsions were all confounded with the rocks of unquestionably aqueous origin.^ What we now recognize to be memorials of these former injections and propulsions were all confounded with the rocks of unquestionably aqueous origin.

^ Reviewing the evidence of these changes, he recognized that the sea now covers tracts that were once dry land, and that land will one day reappear where there is now sea.

^ These bodies were found to consist of elements all of which had been recognized as entering into the constitution of the earth.

.The last great teacher by whom these antiquated doctrines were formulated into a system and promulgated to the world was Abraham Gottlob W Werner (1749-1815), the most illustrious German mineral ogist and geognost of the second half of the 18th century.^ The last great teacher by whom these antiquated doctrines were formulated into a system and promulgated to the world was Abraham Gottlob W Werner (1749-1815), the most illustrious German mineral ogist and geognost of the second half of the 18th century.

^ The term " geology,"' descriptive of this branch of the investigation of nature, was not proposed until the last quarter of the 18th century by Jean Andre De Luc (1727-1817) and Horace Benedict De Saussure (1740-1749).

^ One good result of the controversy, however, was to be seen in the large collections of these " formed stones" that were gathered together in the cabinets and museums of the 17th and 18th centuries.

.While still under twenty-six years of age, he was appointed teacher of mining and mineralogy at the Mining Academy of Freiberg in Saxony - a post which he continued to fill up to the end of his life.^ While still under twenty-six years of age, he was appointed teacher of mining and mineralogy at the Mining Academy of Freiberg in Saxony - a post which he continued to fill up to the end of his life.

^ If you continue up the road, keeping the camp on your right, one can gain access to several talc mines further up the canyon.
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^ Just up canyon from the main adit is Warm Spring itself, with several buildings that were constructed a few years before the mines closed.
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.Possessed of great enthusiasm for his subject, clear, methodical and eloquent in his exposition of it, he soon drew around him men from all parts of the world, who repaired to study under the great oracle of what he called geognosy (Gr.^ Possessed of great enthusiasm for his subject, clear, methodical and eloquent in his exposition of it, he soon drew around him men from all parts of the world, who repaired to study under the great oracle of what he called geognosy (Gr.

^ The diluvialists (those who relied on the hypothesis of the Flood) held the field during the 16th, 17th and a great part of the 18th century.

^ The influence of his teaching, however, was subsequently in great part due to the Carmelite friar Generelli, who published an eloquent exposition of Moro's views.

yn, the earth, yvOvvcs, knowledge) or earthknowledge. .Reviving doctrines that had been current long before his time, he taught that the globe was once completely surrounded with an ocean, from which the rocks of the earth's crust were deposited as chemical precipitates, in a certain definite order over the whole planet.^ Reviving doctrines that had been current long before his time, he taught that the globe was once completely surrounded with an ocean, from which the rocks of the earth's crust were deposited as chemical precipitates, in a certain definite order over the whole planet.

^ When a few years later he went to Norway and found to his astonishment that granite, which he had been taught to regard as the oldest chemical precipitate from the universal ocean, could there be seen to have broken through and metamorphosed fossiliferous limestones, and to have sent veins into them, his faith in Werner's order of the succession of the rocks in the earth's crust received a further momentous shock .

^ It must be conceded, however, that the stress which he laid upon the fact that the rocks of the earth's crust were deposited in a definite order had an important influence in directing attention to this subject, and in preparing the way for a more natural system, based not on mere mineralogical characters, but having regard to the organic remains, which were now being gathered in ever-increasing numbers and variety from stratified formations of many different ages and from all parts of the globe.

.Among these " universal formations " of aqueous origin were included many rocks, which have long been recognized to have been once molten, and to have risen from below into the upper parts of the terrestrial crust.^ Among these " universal formations " of aqueous origin were included many rocks, which have long been recognized to have been once molten, and to have risen from below into the upper parts of the terrestrial crust.

^ He believed that these various aqueous accumulations had been consolidated by subterranean heat, that the oldest and lowest rocks had suffered most from this action, that into these more deep-seated masses subsequent veins and larger bodies of molten matter were injected from below, and thus that what was originally loose detritus eventually became changed in such crystalline schists as are now found in mountain-chains.

^ Although Desmarest had traced in Auvergne;a long succession of volcanic eruptions, of which the oldest went back to a remote period of time, and although he had shown that this succession, coupled with the records of contemporaneous denudation, might be used in defining epochs of geological history, it was not until many years after his day that volcanic action came to be recognized as a normal part of the mechanism of our globe, which had been in operation from the remotest past, and which had left numerous records among the rocks of the terrestrial crust.

.Werner, following the old tradition, looked upon volcanoes as modern features in the history of the planet, which could not have come into existence until a sufficient amount of vegetation had been buried to furnish fuel for their maintenance.^ Werner, following the old tradition, looked upon volcanoes as modern features in the history of the planet, which could not have come into existence until a sufficient amount of vegetation had been buried to furnish fuel for their maintenance.

^ He calculated that the first volcanoes could not arise until some 50,000 years after the beginning of the world, by which time a sufficient extent of dense vegetation had been buried in the earth to supply them with fuel.

^ Another branch of physiographical geology which could only come into existence after most of the other departments of the science had made large progress, deals with the evolution of the framework of each country and of the several continents and oceans of the globe.

.Hence he attached but little importance to them, and did not include in his system of rocks any division of volcanic or igneous materials.^ Hence he attached but little importance to them, and did not include in his system of rocks any division of volcanic or igneous materials.

^ They include those masses of mineral matter which, unlike the igneous rocks, can be traced back to a definite origin on the surface of the earth.

^ The spur road mentioned above that heads north delivers you right into the Shoshone volcanics but also includes some Miocene granitic rocks.
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.From the predominant part assigned by him to the sea in the accumulation of the materials of the visible part of the earth, Werner and his school were known as "Neptunists."^ From the predominant part assigned by him to the sea in the accumulation of the materials of the visible part of the earth, Werner and his school were known as "Neptunists."

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ To the geologist the presence of mineral solutions in sea-water is a fact of much importance, for it explains the origin of a considerable part of the stratified rocks of the earth's crust.

.But many years before the Saxon professor began to teach, clear evidence had been produced from central France that basalt, one Origin of the rocks claimed by him as a chemical precipitate and Orig; . a universal formation, is a lava which has been poured basalt out in a molten state at various widely separated periods of time and at many different places.^ But many years before the Saxon professor began to teach, clear evidence had been produced from central France that basalt , one Origin of the rocks claimed by him as a chemical precipitate and Orig; .

^ Many of the chemical precipitates were shown to be masses that had been erupted in a molten state from below.

^ Geology: The origin of Mushroom Rock has been debated for many years.
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.So far back as 1752 J. E. Guettard (1715-1786) had shown that the basaltic rocks of Auvergne are true lavas, which have flowed out in streams from groups of once active cones.^ So far back as 1752 J. E. Guettard (1715-1786) had shown that the basaltic rocks of Auvergne are true lavas, which have flowed out in streams from groups of once active cones.

^ If, on the other hand, the lava crosses a stream, it forms a massive dam , above which the water is ponded back so as to form a lake.

^ This must mainly be decided on the evidence of organic remains, as shown in Part VI., where the grouping of the stratified rocks into formations and systems is described.

.Eleven years later the observation was confirmed and greatly extended by Nicholas Desmarest (1725-1815), who, during a long course of years, worked out and mapped the complicated volcanic records of that interesting region, and demonstrated to all who were willing impartially to examine the evidence the true volcanic nature of basalt.^ Eleven years later the observation was confirmed and greatly extended by Nicholas Desmarest (1725-1815), who, during a long course of years, worked out and mapped the complicated volcanic records of that interesting region, and demonstrated to all who were willing impartially to examine the evidence the true volcanic nature of basalt.

^ In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

.These views found acceptance from some observers, but they were vehemently opposed by the followers of Werner, who, by the force of his genius, made his theoretical conceptions predominate all over Europe.^ These views found acceptance from some observers, but they were vehemently opposed by the followers of Werner, who, by the force of his genius, made his theoretical conceptions predominate all over Europe.

^ These bodies were found to consist of elements all of which had been recognized as entering into the constitution of the earth.

^ The Christian church had meanwhile arisen to power all over Europe , and adjudged as heretics all who ventured to impugn any of her dogmas.

.The controversy as to the origin of basalt was waged with great vigour during the later decades of the 18th century.^ The controversy as to the origin of basalt was waged with great vigour during the later decades of the 18th century.

^ During the progress of the controversy between the two great opposing factions in the later portion of the 18th and the first three decades of the 19th century, those who espoused the Vulcanist cause were intent on proving that certain rocks, which are intercalated among the stratified formations and which were claimed by the Neptunists as obviously formed by water, are nevertheless of truly igneous origin.

^ One good result of the controversy, however, was to be seen in the large collections of these " formed stones" that were gathered together in the cabinets and museums of the 17th and 18th centuries.

.Desmarest took no part in it.^ Desmarest took no part in it.

.He had accumulated such conclusive proof of the correctness of his deductions, and had so fully expounded the clearness of the evidence in their favour furnished by the region of Auvergne, that, when any one came to consult him on the subject, he contented himself with giving the advice to " go and see."^ He had accumulated such conclusive proof of the correctness of his deductions, and had so fully expounded the clearness of the evidence in their favour furnished by the region of Auvergne, that, when any one came to consult him on the subject, he contented himself with giving the advice to " go and see."

^ It may readily be supposed that any proofs of the contemporaneous intercalation of such sheets would be eagerly seized upon by the Neptunists in favour of their aqueous theory.

^ Such a chain may be the result of one colossal disturbance; but those of high geological antiquity usually furnish proofs of successive uplifts with more or less intervening denudation.

.While the debate was in progress on the continent, the subject was approached from a new and independent point of view by Hutton in Scotland.^ While the debate was in progress on the continent, the subject was approached from a new and independent point of view by Hutton in Scotland .

^ He approached the subject from an opposite and less philosophical point of view than that of Lamarck, coming to it with certain preconceived notions, which affected all his subsequent writings.

^ The former geologist, approaching the question from a novel point of view, has estimated the total quantity of sodium in the water of the ocean and the quantity of that element received annually by the ocean from the denudation of the land.

.This illustrious philosopher, as already stated, realized the importance of the internal heat of the globe in consolidating the sedimentary rocks, and believed that molten material from the earth's interior has been protruded from below into the overlying crust.^ An inquiry into the materials of the earth's substance.

^ This illustrious philosopher, as already stated, realized the importance of the internal heat of the globe in consolidating the sedimentary rocks, and believed that molten material from the earth's interior has been protruded from below into the overlying crust.

^ He believed that these various aqueous accumulations had been consolidated by subterranean heat, that the oldest and lowest rocks had suffered most from this action, that into these more deep-seated masses subsequent veins and larger bodies of molten matter were injected from below, and thus that what was originally loose detritus eventually became changed in such crystalline schists as are now found in mountain-chains.

.Some of the material thus injected could be recognized, he thought, in granite and in the various dark massive rocks which, known in Scotland under the name of " whinstone," were afterwards called " Trap," and are now grouped under various names, such as basalt, dolerite and diorite.^ Some of the material thus injected could be recognized, he thought, in granite and in the various dark massive rocks which, known in Scotland under the name of " whinstone," were afterwards called " Trap ," and are now grouped under various names, such as basalt, dolerite and diorite .

^ The oldest known rocks present none of the characters of molten material that has cooled and hardened in the air, like the various forms of recent lava.

^ Under this term geologists are accustomed to class not only solid stone, such as granite and limestone, but also less coherent materials such as clay , peat and even loose sand.

.So important a share did Hutton thus assign to the internal heat in the geological evolution of the planet, that he and those who adopted the same opinions were styled " Plutonists," or, especially where they concerned themselves with the volcanic origin of basalt, " Vulcanists."^ So important a share did Hutton thus assign to the internal heat in the geological evolution of the planet, that he and those who adopted the same opinions were styled " Plutonists," or, especially where they concerned themselves with the volcanic origin of basalt, " Vulcanists."

^ In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

.The geological world was thus divided into two hostile camps, that of the Neptunists or Wernerians, and that of the Plutonists, Vulcanists or Huttonians.^ The geological world was thus divided into two hostile camps, that of the Neptunists or Wernerians, and that of the Plutonists, Vulcanists or Huttonians.

.After many years of futile controversy the first serious weakening of the position of the dominant Neptunist school arose from the defection of some of the most prominent of Werner's pupils.^ After many years of futile controversy the first serious weakening of the position of the dominant Neptunist school arose from the defection of some of the most prominent of Werner's pupils.

^ Some years later he expanded this first essay into a larger work in two volumes, which were published in 1795 with the title of Theory of the Earth, with Proofs and Illustrations.

^ He, too, was trained by Werner himself, and proved to be the most illustrious pupil of the Saxon professor.

.In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.^ In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.

^ Eleven years later the observation was confirmed and greatly extended by Nicholas Desmarest (1725-1815), who, during a long course of years, worked out and mapped the complicated volcanic records of that interesting region, and demonstrated to all who were willing impartially to examine the evidence the true volcanic nature of basalt.

^ Desmarest, in his investigation of the volcanic history of Auvergne, was the first observer to perceive by what a long process of sculpture the present configuration of the land has been brought about.

.Having thus to relinquish one of the fundamental articles of the Freiberg faith, he was subsequently led to modify his adherence to others until, as he himself confessed, his views came almost wholly to agree with those of Hutton.^ Having thus to relinquish one of the fundamental articles of the Freiberg faith, he was subsequently led to modify his adherence to others until, as he himself confessed, his views came almost wholly to agree with those of Hutton.

^ While one after another of the Freiberg doctrines crumbled away before him, he was now able to interrogate nature on a wider field than the narrow limits of Saxony, and he was thus gradually led to embrace the tenets of the opposite school.

^ Playfair, on the other hand, expressed himself in such clear and graceful language as to command general attention, and to gain wide acceptance for his master's views.

.Not less complete, and even more important, was the conversion of the great Leopold von Buch (1774-1853).^ Not less complete, and even more important, was the conversion of the great Leopold von Buch (1774-1853).

.He, too, was trained by Werner himself, and proved to be the most illustrious pupil of the Saxon professor.^ He, too, was trained by Werner himself, and proved to be the most illustrious pupil of the Saxon professor.

^ After many years of futile controversy the first serious weakening of the position of the dominant Neptunist school arose from the defection of some of the most prominent of Werner's pupils.

.Full of admiration for the Neptunism in which he had been reared, he, in his earliest separate work, maintained the aqueous origin of basalt, and contrasted the wide field opened up to the spirit of observation by his master's teaching with the narrower outlook offered by " the volcanic theory."^ Full of admiration for the Neptunism in which he had been reared, he, in his earliest separate work, maintained the aqueous origin of basalt, and contrasted the wide field opened up to the spirit of observation by his master's teaching with the narrower outlook offered by " the volcanic theory."

^ In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.

.But a little further acquaintance with the facts of nature led Von Buch also to abandon his earlier prepossessions.^ But a little further acquaintance with the facts of nature led Von Buch also to abandon his earlier prepossessions.

.It was a personal visit to the volcanic region of Auvergne that first opened his eyes, and led him to recant what he had believed and written about basalt.^ It was a personal visit to the volcanic region of Auvergne that first opened his eyes, and led him to recant what he had believed and written about basalt.

^ In particular Jean Francois D'Aubuisson de Voisins (1769-1819), who had written a treatise on the aqueous origin of the basalts of Saxony, went afterwards to Auvergne, where he was speedily a convert to the views expounded by Desmarest as to the volcanic nature of basalt.

^ In the lowest strata, representing the first age, none of the fossils were believed by him to have any living representatives, and he called these rocks " Primordial."

.But the abandonment of so essential a portion of the Wernerian creed prepared the way for further relinquishments.^ But the abandonment of so essential a portion of the Wernerian creed prepared the way for further relinquishments.

.When a few years later he went to Norway and found to his astonishment that granite, which he had been taught to regard as the oldest chemical precipitate from the universal ocean, could there be seen to have broken through and metamorphosed fossiliferous limestones, and to have sent veins into them, his faith in Werner's order of the succession of the rocks in the earth's crust received a further momentous shock.^ When a few years later he went to Norway and found to his astonishment that granite, which he had been taught to regard as the oldest chemical precipitate from the universal ocean, could there be seen to have broken through and metamorphosed fossiliferous limestones, and to have sent veins into them, his faith in Werner's order of the succession of the rocks in the earth's crust received a further momentous shock .

^ Hence the relative purity of limestones may be roughly determined by examining their weathered surfaces, where, if they contain much sand, the grains will be seen projecting from the calcareous matrix, and where, should the rock be very ferruginous, the yellow hydrous peroxide, or ochre, will be found as a powdery crust.

^ We have seen, for instance, that according to the teaching of Werner the oldest rocks were first precipitated from solution in the universal ocean to form the mountains, that the vertical position of their strata was original, that as the waters subsided successive formations were deposited and laid bare, and that finally the superfluous portion of the ocean was whisked away into space by some unexplained co-operation of another planetary body.

.While one after another of the Freiberg doctrines crumbled away before him, he was now able to interrogate nature on a wider field than the narrow limits of Saxony, and he was thus gradually led to embrace the tenets of the opposite school.^ While one after another of the Freiberg doctrines crumbled away before him, he was now able to interrogate nature on a wider field than the narrow limits of Saxony, and he was thus gradually led to embrace the tenets of the opposite school.

^ Having thus to relinquish one of the fundamental articles of the Freiberg faith, he was subsequently led to modify his adherence to others until, as he himself confessed, his views came almost wholly to agree with those of Hutton.

^ Though this sweeping deduction must be allowed to detract from the value of Lamarck's work, there can be no doubt that he realized, more fully than any one had done before him, the efficacy of plants and animals as agents of geological change.

.His commanding position, as the most accomplished geologist on the continent, gave great importance to his recantation of the Neptunist creed.^ His commanding position, as the most accomplished geologist on the continent, gave great importance to his recantation of the Neptunist creed.

^ After many years of futile controversy the first serious weakening of the position of the dominant Neptunist school arose from the defection of some of the most prominent of Werner's pupils.

.His defection indeed was the severest blow that this creed had yet sustained.^ His defection indeed was the severest blow that this creed had yet sustained.

.It may be said to have rung the knell of Wernerianism, which thereafter rapidly declined in influence, while Plutonism came steadily to the front,where it has ever since remained.^ It may be said to have rung the knell of Wernerianism, which thereafter rapidly declined in influence, while Plutonism came steadily to the front,where it has ever since remained.

.Although Desmarest had traced in Auvergne;a long succession of volcanic eruptions, of which the oldest went back to a remote period of time, and although he had shown that this succession, coupled with the records of contemporaneous denudation, might be used in defining epochs of geological history, it was not until many years after his day that volcanic action came to be recognized as a normal part of the mechanism of our globe, which had been in operation from the remotest past, and which had left numerous records among the rocks of the terrestrial crust.^ This section might be called geological history.

^ Although Desmarest had traced in Auvergne;a long succession of volcanic eruptions, of which the oldest went back to a remote period of time, and although he had shown that this succession, coupled with the records of contemporaneous denudation, might be used in defining epochs of geological history, it was not until many years after his day that volcanic action came to be recognized as a normal part of the mechanism of our globe, which had been in operation from the remotest past, and which had left numerous records among the rocks of the terrestrial crust.

^ Eleven years later the observation was confirmed and greatly extended by Nicholas Desmarest (1725-1815), who, during a long course of years, worked out and mapped the complicated volcanic records of that interesting region, and demonstrated to all who were willing impartially to examine the evidence the true volcanic nature of basalt.

.During the progress of the controversy between the two great opposing factions in the later portion of the 18th and the first three decades of the 19th century, those who espoused the Vulcanist cause were intent on proving that certain rocks, which are intercalated among the stratified formations and which were claimed by the Neptunists as obviously formed by water, are nevertheless of truly igneous origin.^ During the progress of the controversy between the two great opposing factions in the later portion of the 18th and the first three decades of the 19th century, those who espoused the Vulcanist cause were intent on proving that certain rocks, which are intercalated among the stratified formations and which were claimed by the Neptunists as obviously formed by water, are nevertheless of truly igneous origin.

^ From their mode of origin this great class of rocks has been called " igneous " or " eruptive."

^ The controversy as to the origin of basalt was waged with great vigour during the later decades of the 18th century.

.These observers fixed their eyes on the evidence that the material of such rocks, instead of having been deposited from aqueous solution, had once been actually; molten, and had in that condition been thrust between the strata, had enveloped portions of them, and had indurated or otherwise altered them.^ These observers fixed their eyes on the evidence that the material of such rocks, instead of having been deposited from aqueous solution, had once been actually; molten, and had in that condition been thrust between the strata, had enveloped portions of them, and had indurated or otherwise altered them.

^ Sometimes the walls have separated and molten rock has risen from below and solidified between them as a dike .

^ These materials arise either from the explosion of lava by the sudden expansion of the dissolved vapours and gases, as the molten rock rises to the surface, or from the breaking up and expulsion of portions of the walls of the vent, or of the lava, which happens to have solidified within these walls.

.They spoke of these masses as " unerupted lavas "; and undoubtedly in innumerable instances they were right.^ They spoke of these masses as " unerupted lavas "; and undoubtedly in innumerable instances they were right.

.But their zeal to establish an intrusive origin led them to overlook the proofs that some intercalated sheets of igneous material had not been injected into the strata, but had been poured out at the surface as truly volcanic discharges, and therefore belonged to the ancient periods represented by the strata between which they are interposed.^ But their zeal to establish an intrusive origin led them to overlook the proofs that some intercalated sheets of igneous material had not been injected into the strata, but had been poured out at the surface as truly volcanic discharges, and therefore belonged to the ancient periods represented by the strata between which they are interposed.

^ Intrusive sheets are distinguishable from true contemporaneously intercalated lavas by not keeping always to the same platform , but breaking across and altering the contiguous strata, and by the closeness of their texture where they come in contact with the contiguous rocks, which, being cold, chilled the molten material and caused it to consolidate on its outer margins more rapidly than in its interior.

^ It may readily be supposed that any proofs of the contemporaneous intercalation of such sheets would be eagerly seized upon by the Neptunists in favour of their aqueous theory.

.It may readily be supposed that any proofs of the contemporaneous intercalation of such sheets would be eagerly seized upon by the Neptunists in favour of their aqueous theory.^ It may readily be supposed that any proofs of the contemporaneous intercalation of such sheets would be eagerly seized upon by the Neptunists in favour of their aqueous theory.

^ It may be said that the absence of such proof ought not to invalidate the assertion until a far wider area of the earth's surface has been geologically studied.

.The influence of the ancient belief that " burning mountains " could only rise from the combustion of subterranean inflammable materials extended even into the ranks of the Vulcanists, so far at least as to lead to a general acquiescence in the assumption that volcanoes appeared to belong to a late phase in the history of the planet.^ The influence of the ancient belief that " burning mountains " could only rise from the combustion of subterranean inflammable materials extended even into the ranks of the Vulcanists, so far at least as to lead to a general acquiescence in the assumption that volcanoes appeared to belong to a late phase in the history of the planet.

^ He thought that the interior of our planet may " be a fluid mass, melted, but unchanged by the action of heat "; and, far from connecting volcanoes with the combustion of inflammable substances, as had been the prevalent belief for so many centuries, he looked upon them as a beneficent provision of " spiracles to the subterranean furnace , in order to prevent the unnecessary elevation of land and fatal effects of earthquakes."

^ Still under the old misconception that volcanoes are due to the combustion of inflammable materials, which he thought might be set on fire by the spontaneous combustion of pyritous strata, he supposed that, by the sudden access of large bodies of water to these subterranean fires, vapour is produced in such quantity and with such force as to give rise to the shock.

.It was not until after considerable progress had been made in determining the palaeontological distinctions and order of succession of the stratified formations of the earth's crust that it became possible to trace among these formations a succession of volcanic episodes which were contemporaneous with them.^ It was not until after considerable progress had been made in determining the palaeontological distinctions and order of succession of the stratified formations of the earth's crust that it became possible to trace among these formations a succession of volcanic episodes which were contemporaneous with them.

^ From palaeontological geology it receives in well-determined fossil remains a clue by which to discriminate the different stratified formations, and to trace the grand onward march of organized existence upon this planet.

^ When Soulavie, Cuvier and Brongniart in France, and William Smith in England, showed that the rock formations of the earth's crust could be arranged in chronological order, and could be recognized far and wide by means of their enclosed organic remains, the vast significance of these remains in geological research was speedily realized, and palaeontological geology at once entered on a new and enlarged phase of development.

.In no part of the world has an ampler record of such episodes been preserved than in the British Isles.^ In no part of the world has an ampler record of such episodes been preserved than in the British Isles.

^ No record has been discovered of such accompanying devastation.

^ In the British Isles, for example, the volcanic record is remarkably full for the long series of ages from Cambrian to Permian time, and again for the older Tertiary period.

.It was natural, therefore, that the subject should there receive most attention.^ It was natural, therefore, that the subject should there receive most attention.

^ The latter receives most attention, as it undoubtedly is the more important; but the former ought not to be omitted in any survey of the general waste of the earth's surface.

.As far back as 1820 Ami Boue (1794-1881) showed that the Old Red Sandstone of Scotland includes a great series of volcanic rocks, and that other rocks of volcanic origin are associated with the Carboniferous formations.^ Catskill red sandstone; Old .

^ As far back as 1820 Ami Boue (1794-1881) showed that the Old Red Sandstone of Scotland includes a great series of volcanic rocks, and that other rocks of volcanic origin are associated with the Carboniferous formations.

^ Red Sandstone type: the strata below show the .

H. T.
de la .Beche (1796-1855) afterwards traced proofs of contemporaneous eruptions among the Devonian rocks of the south-west of England.^ Beche (1796-1855) afterwards traced proofs of contemporaneous eruptions among the Devonian rocks of the south-west of England.

^ It can be traced across Belgium into the Boulonnais, and may not improbably run beneath the Secondary and Tertiary rocks of the south of England.

^ Admirable examples of these features are to be seen along the west coast of Europe from the south of England to the north of Norway.

.Adam Sedgwick (1785-1873) showed, first in the Lake District, and afterwards in North Wales, the presence of abundant volcanic sheets among the oldest divisions of the Palaeozoic series; while Roderick Impey Murchison (1792-1871) made similar discoveries among the Lower Silurian rocks.^ Adam Sedgwick (1785-1873) showed, first in the Lake District , and afterwards in North Wales , the presence of abundant volcanic sheets among the oldest divisions of the Palaeozoic series; while Roderick Impey Murchison (1792-1871) made similar discoveries among the Lower Silurian rocks.

^ Applying the method, in the first instance, to the highly plicated Silurian rocks of the south of Scotland, he found that by means of graptolites he was able to work out the structure of the ground.

^ He showed that it was not by submergence in a sea cumbered with floating ice, but by the former presence of vast glaciers or sheets of ice that the Drift and erratic blocks had been distributed.

.From the time of these pioneers the volcanic history of the country has been worked out by many observers until it is now known with a fulness as yet unattained in any other region.^ From the time of these pioneers the volcanic history of the country has been worked out by many observers until it is now known with a fulness as yet unattained in any other region.

^ He believed that in that history evidence can be recognized of the occurrence of many sudden and disastrous revolutions, which, to judge from their effects on the animal life of the time, must have exceeded in violence anything we can conceive at the present day, and must have been brought about by other agencies than those which are now in operation.

^ From that time onward, volcanic eruptions succeeded each other, not only on the emerged land, but on the sea-floor, over which the ejected material spread in an ever augmenting thickness of sedimentary strata.

Growth of Opinion regarding Earthquakes

.We have seen how crude were the conceptions of the ancients regarding the causes of volcanic action, and that they connected volcanoes and earthquakes as results of the commotion of wind imprisoned within subterranean caverns and passages.^ These crude conceptions of the nature of volcanic action, and the cause of earthquakes, continued to prevail for many centuries.

^ We have seen that in classical antiquity they were looked on as the results of the movements of wind imprisoned within the earth.

^ We have seen how crude were the conceptions of the ancients regarding the causes of volcanic action, and that they connected volcanoes and earthquakes as results of the commotion of wind imprisoned within subterranean caverns and passages.

.One of the earliest treatises, in which the phenomena of terrestrial movements were discussed in the spirit of modern science, was the posthumous collection of papers by Robert Hooke (1635-1703), entitled Lectures and Discourses of Earthquakes and Subterranean Eruptions, where the probable agency of earthquakes in upheaving and depressing land is fully considered, but without any definite pronouncement as to the author's conception of its origin.^ One of the earliest treatises, in which the phenomena of terrestrial movements were discussed in the spirit of modern science, was the posthumous collection of papers by Robert Hooke (1635-1703), entitled Lectures and Discourses of Earthquakes and Subterranean Eruptions, where the probable agency of earthquakes in upheaving and depressing land is fully considered, but without any definite pronouncement as to the author's conception of its origin.

^ It thus appears that with regard to subterranean geological operations, no advance was made during the time of the Greeks and Romans as to the theoretical explanation of these phenomena; but a considerable body of facts was collected, especially as to the effects of earthquakes and the occurrence of volcanic eruptions.

^ Some of them are referable to movements of the terrestrial crust whereby depressions arise on the surface of the land, as has been noted after earthquakes.

Hooke still associated earthquakes with volcanic action, and connected both with what he called " the general congregation of sulphurous subterraneous vapours." He conceived that some kind of " fermentation " takes place within the earth, and that the materials which catch fire and give rise to eruptions or earthquakes are analogous to those that constitute gunpowder. The first essay wherein earthquakes are treated from the modern point of view as the results of a shock that sends waves through the crust of the earth was written by the Rev. John Michell, and communicated to the Royal Society in the year 1760. Still under the old misconception that volcanoes are due to the combustion of inflammable materials, which he thought might be set on fire by the spontaneous combustion of pyritous strata, he supposed that, by the sudden access of large bodies of water to these subterranean fires, vapour is produced in such quantity and with such force as to give rise to the shock. .From the centre of origin of this shock waves, he thought, are propagated through the earth, which are largest at the start and gradually diminish as they travel outwards.^ From the centre of origin of this shock waves, he thought, are propagated through the earth, which are largest at the start and gradually diminish as they travel outwards.

^ The origin of the minerals is thought to be from hydrothermal fluids circulating through the Furnace Creek formation.
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^ Observations on earthquake motion by Dr John Milne and others, show that the rate and character of the waves transmitted through the interior of the earth differ in a marked degree from those propagated along the crust.

.By drawing lines at different places in the direction of the track of these waves, he believed that the place of common intersection of these lines would be nearly the centre of the disturbance.^ By drawing lines at different places in the direction of the track of these waves, he believed that the place of common intersection of these lines would be nearly the centre of the disturbance.

^ If these colossal disturbances occurred rapidly, they would give rise to cataclysms of inconceivable magnitude over the surface of the globe.

^ By the collapse of the roofs of these caverns, valleys might be originated at the surface, while the solid intervening walls would remain in place and form mountains.

.In this way he showed that the great Lisbon earthquake of 1755 had its focus under the Atlantic, somewhere between the latitudes of Lisbon and Oporto, and he estimated that the depth at which it originated could not be much less than 1 m., and probably did not exceed 3 m.^ In this way he showed that the great Lisbon earthquake of 1755 had its focus under the Atlantic , somewhere between the latitudes of Lisbon and Oporto , and he estimated that the depth at which it originated could not be much less than 1 m., and probably did not exceed 3 m.

^ From time to time the surface suffers calamitous devastation from earthquakes, when portions of the crust under great strain suddenly give way.

^ There is now a general agreement that between the great world-shaking earthquakes and volcanic phenomena, no immediate and intimate relationship can be traced, though they may be connected in ways which are not yet perceived.

.Michell, however, misconceived the character of the waves which he described, seeing that he believed them to be due to the actual propagation of the vapour itself underneath the surface of the earth.^ Michell, however, misconceived the character of the waves which he described, seeing that he believed them to be due to the actual propagation of the vapour itself underneath the surface of the earth.

^ The general characters of the atmosphere are described in separate articles (see especially Atmosphere ; Meteorology ).

^ In these works he described the stratigraphical relations and general characters of the various geological formations in his little principality; and taking them as indicative of a general order of succession, he traced what he believed to have been a series of revolutions through which the earth has passed.

.A century had almost passed after the date of his essay before modern scientific methods of observation and the use of recording instruments began to be applied to the study of earthquake phenomena.^ A century had almost passed after the date of his essay before modern scientific methods of observation and the use of recording instruments began to be applied to the study of earthquake phenomena.

^ Though the expression " the solid earth " has become proverbial, it appears singularly inappropriate in the light of the results obtained in recent years by the use of delicate instruments of observation.

^ In using these terms we unconsciously allow the idea of relative date to arise prominently before us.

.In 1846 Robert Mallet (1810-1881) published an important paper "On the Dynamics of Earthquakes " in the Transactions of the Royal Irish Academy. From that time onward he continued to devote his energies to the investigation, studying the effects of the Calabrian earthquake of 18J7, experimenting on the transmission of waves of shock through various materials, caused by exploding charges of gunpowder, and collecting all the information to be obtained on the subject.^ From that time onward he continued to devote his energies to the investigation, studying the effects of the Calabrian earthquake of 18J7, experimenting on the transmission of waves of shock through various materials, caused by exploding charges of gunpowder, and collecting all the information to be obtained on the subject.

^ In 1846 Robert Mallet (1810-1881) published an important paper "On the Dynamics of Earthquakes " in the Transactions of the Royal Irish Academy.

^ Subsequently Induced Structures After their accumulation, whether as stratified or eruptive masses, all kinds of rocks have been subject to various changes, and have acquired in consequence a variety of superinduced structures.

.His writings, and especially his work in two volumes on The First Principles of Observational Seismology, must be regarded as having laid the foundations of this branch of modern geology (see Earthquake; Seismometer).^ His writings, and especially his work in two volumes on The First Principles of Observational Seismology, must be regarded as having laid the foundations of this branch of modern geology (see Earthquake ; Seismometer ).

^ Of modern English works, Sir A. Geikie's Text Book of Geology (4th ed., 1903) occupies the first place; the work of T. C. Chamberlin and R. D. Salisbury , Geology; Earth History (3 vols., 1905-1906), is especially valuable for American geology.

^ To the Italian school, as especially typified in Steno, must be assigned the honour of having thus begun to lay firmly and truly the first foundation stones of the modern science of LMazzaro geology.

History of the Evolution of Stratigraphical Geology

.Men had long been familiar with the evidence that the present dry land once lay under the sea, before they began to realize that the rocks, of which the land consists, contain a record of many alternations of land and sea, and relics of a long succession of plants and animals from early and simple types up to the manifold and complex forms of to-day.^ Men had long been familiar with the evidence that the present dry land once lay under the sea, before they began to realize that the rocks, of which the land consists, contain a record of many alternations of land and sea, and relics of a long succession of plants and animals from early and simple types up to the manifold and complex forms of to-day.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ In the first place, the organization of the most ancient plants and animals furnishes no indication that they had to contend with any greater violence of storm , flood, wave or ocean-current than is familiar to their modern descendants.

.In countries where coal-mining had been prosecuted for generations, it had been recognized that the rocks consist of strata superposed on each other in a definite order, which was found to extend over the whole of a district.^ In countries where coal-mining had been prosecuted for generations, it had been recognized that the rocks consist of strata superposed on each other in a definite order, which was found to extend over the whole of a district.

^ Their materials have been laid down in laminae, layers and strata, or beds, pointing generally to the intermittent deposition of the sediments of which they consist.

^ From the key which his researches supplied, it was possible to recognize in other countries the same order of formations and the same sequence of fossils, so that, in the course of a few years, representatives of the Silurian system were found far and wide over the globe.

.As far back as 1719 John Strachey drew attention to this fact in a communication published in the Philosophical Transactions. John Michell (1760), in the paper on earthquakes already cited, showed that he had acquired a clear understanding of the order of succession among stratified formations, and perceived that to disturbances of the terrestrial crust must be ascribed the fact that the lower or older and more inclined strata form the mountains, while the younger and more horizontal strata are spread over the plains.^ John Michell (1760), in the paper on earthquakes already cited, showed that he had acquired a clear understanding of the order of succession among stratified formations, and perceived that to disturbances of the terrestrial crust must be ascribed the fact that the lower or older and more inclined strata form the mountains, while the younger and more horizontal strata are spread over the plains.

^ As far back as 1719 John Strachey drew attention to this fact in a communication published in the Philosophical Transactions.

^ It must be conceded, however, that the stress which he laid upon the fact that the rocks of the earth's crust were deposited in a definite order had an important influence in directing attention to this subject, and in preparing the way for a more natural system, based not on mere mineralogical characters, but having regard to the organic remains, which were now being gathered in ever-increasing numbers and variety from stratified formations of many different ages and from all parts of the globe.

.In Italy G. Arduino (1713-1795) classified the rocks in the north of the peninsula as Primitive, Secondary, Tertiary and Volcanic.^ In Italy G. Arduino (1713-1795) classified the rocks in the north of the peninsula as Primitive, Secondary, Tertiary and Volcanic.

^ It can be traced across Belgium into the Boulonnais, and may not improbably run beneath the Secondary and Tertiary rocks of the south of England.

^ The spur road mentioned above that heads north delivers you right into the Shoshone volcanics but also includes some Miocene granitic rocks.
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.A similar threefold order was announced for the Harz and Erzgebirge by J. G. Lehmann in 1756. He recognized in that region an ancient series of rocks in inclined or vertical strata, which rise to the tops of the hills and descend to an unknown depth into the interior.^ A similar threefold order was announced for the Harz and Erzgebirge by J. G. Lehmann in 1756.

^ He recognized in that region an ancient series of rocks in inclined or vertical strata, which rise to the tops of the hills and descend to an unknown depth into the interior.

^ After the revival of learning the ancient problem presented by fossil shells imbedded in the rocks of the interior of many countries received renewed attention.

.These masses, he thought, were contemporaneous with the making of the world.^ These masses, he thought, were contemporaneous with the making of the world.

.Next came the Flotzgebirge, consisting of younger sediments, disposed in flat or gently inclined sheets which overlie the first and more disturbed series, and are full of petrified remains of plants and animals.^ Next came the Flotzgebirge, consisting of younger sediments, disposed in flat or gently inclined sheets which overlie the first and more disturbed series, and are full of petrified remains of plants and animals.

^ But it is mainly by the remains of plants and animals imbedded in the rocks that the geologist is guided in unravelling the chronological succession of geological changes.

^ The strata of the fourth series were characterized by carbonaceous shales or slates, containing remains of primordial vegetation, and perhaps equivalents of the first three calcareous series.

.Lastly he included the mountains which have from time to time been formed by local accidents.^ Lastly he included the mountains which have from time to time been formed by local accidents.

.Still more advanced were the conceptions of G. C. Fiichsel, who in the year 1762 published in Latin A History of the Earth and the Sea, based on a History of the Mountains of Thuringia; and in 1773, in German, a Sketch of the most Ancient History of the Earth and Man. In these works he described the stratigraphical relations and general characters of the various geological formations in his little principality; and taking them as indicative of a general order of succession, he traced what he believed to have been a series of revolutions through which the earth has passed.^ Still more advanced were the conceptions of G. C. Fiichsel, who in the year 1762 published in Latin A History of the Earth and the Sea, based on a History of the Mountains of Thuringia ; and in 1773, in German, a Sketch of the most Ancient History of the Earth and Man.

^ In these works he described the stratigraphical relations and general characters of the various geological formations in his little principality; and taking them as indicative of a general order of succession, he traced what he believed to have been a series of revolutions through which the earth has passed.

^ Thus in England the outlines traced by him among the Secondary and Tertiary formations were admirably filled in by Thomas Webster (1773-1844) while the Cretaceous series was worked out in still greater detail in the classic memoirs of William Henry Fitton (1780-1861).

.In interpreting this geological history, he laid great stress on the evidence of the fossils contained in the rocks.^ In interpreting this geological history, he laid great stress on the evidence of the fossils contained in the rocks.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.He recognized that the various formations differ from each other in their enclosed organic remains, and that from these differences the existence of former sea-bottoms and land surfaces can be determined.^ He recognized that the various formations differ from each other in their enclosed organic remains, and that from these differences the existence of former sea-bottoms and land surfaces can be determined.

^ A study of the land-surfaces and sea-floors of the present time shows that there are so many chances against the conservation of the remains of either terrestrial or marine animals and plants that if, as is probable, the same conditions existed in former geological periods, we should regard the occurrence of organic remains among the stratified formations of the earth's crust as generally the result of various fortunate accidents.

^ To him they were not only of deep interest as monuments of former types of existence, but they had an especial value as records of the changes which the country had undergone from sea to land and from land to sea.

.The labours of these pioneers paved the way for the advent of Werner.^ The labours of these pioneers paved the way for the advent of Werner.

.Though the system evolved by this teacher claimed to discard theory and to be established on a basis of observed facts, it rested on a succession of hypotheses, for which no better foundation could be shown than the belief of their author in their validity.^ Though the system evolved by this teacher claimed to discard theory and to be established on a basis of observed facts, it rested on a succession of hypotheses, for which no better foundation could be shown than the belief of their author in their validity.

^ His journeys in Britain and on the continent of Europe had furnished him with material for reflection; and he had gradually evolved a system or theory in which all the scattered facts could be arranged so as to show their mutual dependence and their place in the orderly mechanism of the world.

^ Its object, the author states, was to present some important and novel considerations, which he thought should form the basis of a true theory of the earth.

.Starting from the extremely limited stratigraphical range displayed in the geological structure of Saxony, he took it as a type for the rest of the globe, persuading himself and impressing upon his followers that the rocks of that small kingdom were to be taken as examples of his " universal formations."^ Starting from the extremely limited stratigraphical range displayed in the geological structure of Saxony, he took it as a type for the rest of the globe, persuading himself and impressing upon his followers that the rocks of that small kingdom were to be taken as examples of his " universal formations."

^ In some cases, on the other hand, they protect rocks from decay, while, by the accumulation of their remains, they give rise to extensive formations both upon the land and in the sea.

^ They present in addition other structures which have been superinduced upon them, and which they share with the unstratified or igneous rocks.

.The oldest portion of the series, classed by him as " Primitive," consisted of rocks which he maintained had been deposited from chemical solution.^ The oldest portion of the series, classed by him as " Primitive," consisted of rocks which he maintained had been deposited from chemical solution.

^ If the surrounding area is composed of material that weather chemically by solution, then the playa is covered with halite (rock salt) and other evaporates.
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^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

.Yet they included granite, gneiss, basalt, porphyry and serpentine, which, even in his own day, were by many observers correctly regarded as of igneous origin.^ Yet they included granite, gneiss, basalt, porphyry and serpentine , which, even in his own day, were by many observers correctly regarded as of igneous origin.

^ They include those masses of mineral matter which, unlike the igneous rocks, can be traced back to a definite origin on the surface of the earth.

^ They range from the finest silky slates, or phyllites, up to the coarsest gneisses, which in hand-specimens can hardly be distinguished from granites.

.A later group of rocks, to which he gave the name of " Transition," comprised, in his belief, partly chemical, partly mechanical sediments, and contained the earliest fossil organic remains.^ A later group of rocks, to which he gave the name of " Transition," comprised, in his belief, partly chemical, partly mechanical sediments, and contained the earliest fossil organic remains.

^ The reproductive action of the air arises partly from the effect of the chemical and mechanical disintegration involved in the process of " weathering," and partly from the transporting power of wind and of aerial currents.

^ In limestones containing abundant encrinites, shells, or other organic remains, the weathered surface commonly presents the fossils standing out in relief.

.A third group, for which he reserved Lehmann's name " Flotz," was made up chiefly of mechanical detritus, while youngest of all came the " Alluvial " series of loams, clays, sands, gravels and peat.^ A third group, for which he reserved Lehmann's name " Flotz," was made up chiefly of mechanical detritus, while youngest of all came the " Alluvial " series of loams, clays, sands, gravels and peat .

^ It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet.

^ Barton sands and clays; Ludian series of France.

.It was by the gradual subsidence of the ocean that, as he believed, the general mass of the dry land emerged, the first-formed rocks being left standing up, sometimes on end, to form the mountains, while those of later date, less steeply inclined, occupied successively lower levels down to the flat alluvial accumulations of the plains.^ The first five miles, one is traveling down the canyon along the Hunter Mountain fault zone and crushed granitic rock is obvious at many places.
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^ The multi-colored rock that makes up the mountains on the left is the upper plate that has moved relative to the lower plate which is the metamorphic complex on the right.
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^ In the distance, looking down the road ahead of you, Cambrian sediments, mostly shale and limestone, form the distant ridges on the left.
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Neither Werner, nor any of his followers, ventured to account for what became of the water as the sea-level subsided, though, in despite of their antipathy to anything like speculation, they could not help suggesting, as an answer to the cogent arguments of their opponents, that " one of the celestial bodies which sometimes approach near to the earth may have been able to withdraw a portion of our atmosphere and of our ocean." Nor was any attempt made to explain the extraordinary nature of the supposed chemical precipitates of the universal ocean. .The progress of inquiry even in Werner's lifetime disproved some of the fundamental portions of his system.^ The progress of inquiry even in Werner's lifetime disproved some of the fundamental portions of his system.

.Many of the chemical precipitates were shown to be masses that had been erupted in a molten state from below.^ Many of the chemical precipitates were shown to be masses that had been erupted in a molten state from below.

.His order of succession was found not to hold good; and though he tried to readjust his sequence and to introduce into it modifications to suit new facts, its inherent artificiality led to its speedy decline after his death.^ His order of succession was found not to hold good; and though he tried to readjust his sequence and to introduce into it modifications to suit new facts, its inherent artificiality led to its speedy decline after his death.

^ Though local differences exist in regard to the precise zone in which a given species of organism may make its first appearance, the general order of succession of the organic forms found in the rocks is never inverted.

^ This similarity of succession has been termed homotaxis, a term which expresses the fact that the order in which the leading types of organized existence have appeared upon the earth has been similar even in widely separated regions.

.It must be conceded, however, that the stress which he laid upon the fact that the rocks of the earth's crust were deposited in a definite order had an important influence in directing attention to this subject, and in preparing the way for a more natural system, based not on mere mineralogical characters, but having regard to the organic remains, which were now being gathered in ever-increasing numbers and variety from stratified formations of many different ages and from all parts of the globe.^ Plants contribute by the aggregation of their remains to the formation of stratified deposits.

^ As part of the earth's crust these rocks present characters by which they are strongly differentiated from the stratified series.

^ An important feature in the cosmogony of Leibnitz is the prominent place which he assigned to organic remains in the stratified rocks of the crust.

.It was in France and in England that the foundations of stratigraphy, based upon a knowledge of organic remains, were first successfully laid.^ It was in France and in England that the foundations of stratigraphy, based upon a knowledge of organic remains, were first successfully laid.

^ Smith's labours laid the foundation of stratigraphical geology in England and he was styled even in his lifetime the " Father of English geology."

.Abbe J. L. Giraud-Soulavie (1752-1813), in his Histoire naturelle de la France meridionale, which appeared in seven volumes, subdivided the limestones of Vivarais into five ages, each marked by a distinct assemblage of shells.^ Abbe J. L. Giraud-Soulavie (1752-1813), in his Histoire naturelle de la France meridionale, which appeared in seven volumes, subdivided the limestones of Vivarais into five ages, each marked by a distinct assemblage of shells.

^ The third age was marked by the presence of shells of still existing species.

.In the lowest strata, representing the first age, none of the fossils were believed by him to have any living representatives, and he called these rocks " Primordial."^ In the lowest strata, representing the first age, none of the fossils were believed by him to have any living representatives, and he called these rocks " Primordial."

^ The strata of the fourth series were characterized by carbonaceous shales or slates, containing remains of primordial vegetation, and perhaps equivalents of the first three calcareous series.

^ I have shown that we have reasons for believing that the age, from all these, may be very considerably underestimated.

.In the next group a mingling of living with extinct forms was observable.^ In the next group a mingling of living with extinct forms was observable.

.The third age was marked by the presence of shells of still existing species.^ The third age was marked by the presence of shells of still existing species.

.The strata of the fourth series were characterized by carbonaceous shales or slates, containing remains of primordial vegetation, and perhaps equivalents of the first three calcareous series.^ The strata of the fourth series were characterized by carbonaceous shales or slates, containing remains of primordial vegetation, and perhaps equivalents of the first three calcareous series.

^ The stratified portion of the earth's crust, or what has been called the " geological record," can be subdivided into natural groups, or series of strata, characterized by distinctive organic remains and recognizable by these remains, in spite of great changes in lithological character from place to place.

^ The fifth age was marked by recent deposits containing remains of terrestrial vegetation and of land animals.

.The fifth age was marked by recent deposits containing remains of terrestrial vegetation and of land animals.^ The fifth age was marked by recent deposits containing remains of terrestrial vegetation and of land animals.

^ When the order of succession of organic remains among the stratified rocks has been determined, they become an invaluable guide in the investigation of the relative age of rocks and the structure of the land.

^ To assert that the dry land is made up in great part of rocks that were formed in the sea, and are crowded with the remains of animals, was plainly to impugn the veracity of the Bible .

.It is remarkable that these sagacious conclusions should have been formed and published at a time when the geologists of the Continent were engaged in the controversy about the origin of basalt, or in disputes about the character and stratigraphical position of the supposed universal formations, and when the interest and importance of fossil organic remains still remained unrecognized by the vast majority of the combatants.^ It is remarkable that these sagacious conclusions should have been formed and published at a time when the geologists of the Continent were engaged in the controversy about the origin of basalt, or in disputes about the character and stratigraphical position of the supposed universal formations, and when the interest and importance of fossil organic remains still remained unrecognized by the vast majority of the combatants.

^ During the latter half of the 19th century the most important development of stratigraphical geology was the detailed working out and application of the principle of zonal classification to the fossiliferous formations - that is, the determination of the sequence and distribution of organic remains in these formations, and the arrangement of the strata into zones, each of which is distinguished by a peculiar assemblage of fossil species (see under Part VI.).

^ Each " formation " is distinguished by its own peculiar assemblage of organic remains, by means of which it can be followed and recognized, even amid the crumplings and dislocations of a disturbed region.

.The rocks of the Paris basin display so clearly an orderly arrangement, and are so distinguished for the variety and perfect preservation of their enclosed organic remains, that they could not fail to attract the early notice of observers.^ The rocks of the Paris basin display so clearly an orderly arrangement, and are so distinguished for the variety and perfect preservation of their enclosed organic remains, that they could not fail to attract the early notice of observers.

^ The early experiments of Sir James Hall, already noticed, formed the starting-point for numerous subsequent researches, which have elucidated many points in the origin and history of rocks.

^ Each " formation " is distinguished by its own peculiar assemblage of organic remains, by means of which it can be followed and recognized, even amid the crumplings and dislocations of a disturbed region.

J. 1~;. .Guettard, G. F. Rouelle (1703-1770), N. Desmarest, A. L. Lavoisier (1743-1794) and others made observations in this interesting district.^ Guettard, G. F. Rouelle (1703-1770), N. Desmarest, A. L. Lavoisier (1743-1794) and others made observations in this interesting district.

.But it was reserved for Cuvier (1769-1832) and A. Brongniart (1770-1847) to work out the detailed succession of the Tertiary formations, and to show how each of these is characterized by its own peculiar assemblage of organic remains.^ But it was reserved for Cuvier (1769-1832) and A. Brongniart (1770-1847) to work out the detailed succession of the Tertiary formations, and to show how each of these is characterized by its own peculiar assemblage of organic remains.

^ Thus in England the outlines traced by him among the Secondary and Tertiary formations were admirably filled in by Thomas Webster (1773-1844) while the Cretaceous series was worked out in still greater detail in the classic memoirs of William Henry Fitton (1780-1861).

^ Each " formation " is distinguished by its own peculiar assemblage of organic remains, by means of which it can be followed and recognized, even amid the crumplings and dislocations of a disturbed region.

The later progress of investigation has slightly corrected and greatly amplified the tabular arrangement established by these authors in 1808, but the broad outlines of the Tertiary stratigraphy of the Paris basin remain still as Cuvier and Brongniart left them. .The most important subsequent change in the classification of the Tertiary formations was made by Sir Charles Lye11, who, conceiving in 1828 the idea of a classification of these rocks by reference to their relative proportions of living and extinct species of shells, established, in collaboration with G. P. Deshayes, the now universally accepted divisions Eocene, Miocene and Pliocene.^ These rocks are the Nova formation and form the hanging wall of the Tucki Mountain detachment (Wernicke, et.
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^ These rocks were probably metamorphosed twice: First and most strongly in the Cretaceous and less so during the Tertiary formation of the detachment (Labotka & Albee, 1988; Miller and Wright, 2004).
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^ This concern for the water levels was triggered in the 1970’s by a concern for the continued viability of the Cyprinodon diabolis , the species of pupfish that lives in this most restrictive environment.
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.Long before Cuvier and Brongniart published an account of their researches, another observer had been at work among the Secondary formations of the west of England, and had independently discovered that the component members of these formations were each distinguished by a peculiar group of organic remains; and that this distinction could be used to discriminate them over all the region through which he had traced them.^ All of the water that falls as rain and snow in this broad topographic basin must drain through the narrows of Titus Canyon (hourglass) just before its exit.
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^ Geology: These “peculiar tubular features up to several feet long, parallel to the bedding” (Wright, 1974) (see photo) in the lower member of the Noonday dolomite have variously been explained as filled worm tubes or organic degassing vents.
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The remarkable man who arrived at this far-reaching generalization was William Smith (1769-1839), a land surveyor who, in the prosecution of his professional business, found opportunities of traversing a great part of England, and of putting his deductions to the test. .As the result of these journeys he accumulated materials enough to enable him to produce a geological map of the country, on which the distribution and succession of the rocks were for the first time delineated.^ As the result of these journeys he accumulated materials enough to enable him to produce a geological map of the country, on which the distribution and succession of the rocks were for the first time delineated.

^ And such has been one of its great functions since the beginning of geological time, as is proved by the rocks that form the visible part of the earth's crust, and consist in great part of marine deposits.

^ Similar evidence as to stresses in the terrestrial crust and the important changes which they produce among the rocks may also be obtained on a smaller scale in many non-mountainous countries.

.Smith's labours laid the foundation of stratigraphical geology in England and he was styled even in his lifetime the " Father of English geology."^ Smith's labours laid the foundation of stratigraphical geology in England and he was styled even in his lifetime the " Father of English geology."

^ The publication of Oppel's classic work Die Juraformation Englands, Frankreichs and des sudwestlichen Deutschlands (1856-1858) marked an epoch in the development of stratigraphical geology.

^ It was in France and in England that the foundations of stratigraphy, based upon a knowledge of organic remains, were first successfully laid.

From his day onward the significance of fossil organic remains gained rapidly increasing recognition. .Thus in England the outlines traced by him among the Secondary and Tertiary formations were admirably filled in by Thomas Webster (1773-1844) while the Cretaceous series was worked out in still greater detail in the classic memoirs of William Henry Fitton (1780-1861).^ Thus in England the outlines traced by him among the Secondary and Tertiary formations were admirably filled in by Thomas Webster (1773-1844) while the Cretaceous series was worked out in still greater detail in the classic memoirs of William Henry Fitton (1780-1861).

^ He could distinguish among them an older or Primary series, and a younger or Secondary series; and did not dispute the existence of a Tertiary series claimed by Peter Simon Pallas (1741-1811).

^ It can be traced across Belgium into the Boulonnais, and may not improbably run beneath the Secondary and Tertiary rocks of the south of England.

.There was one stratigraphical domain, however, into which William Smith did not enter.^ There was one stratigraphical domain, however, into which William Smith did not enter.

^ The study, however, continued to be pursuedin Germany, where the influence of Werner's enthusiasm still led men to enter the petrographical rather than the palaeontological domain.

.He traced his sequence of rocks down into the Coal Measures, but contented himself with only a vague reference to what lay underneath that formation.^ He traced his sequence of rocks down into the Coal Measures, but contented himself with only a vague reference to what lay underneath that formation.

^ The varied colors are due to trace elements within this predominantly volcanic formation, especially those associated with the more felsic rocks.
  • VIRTUAL FIELD TRIP 16 January 2010 4:31 UTC www.palomar.edu [Source type: FILTERED WITH BAYES]

^ A short walk down the road reveals strongly deformed rocks of the Wood Canyon formation in the bluffs on the right.
  • VIRTUAL FIELD TRIP 16 January 2010 4:31 UTC www.palomar.edu [Source type: FILTERED WITH BAYES]

.Though some of these underlying rocks had in various countries yielded abundant fossils, they had generally suffered so much from terrestrial disturbances, and their order of succession was consequently often so much obscured throughout western Europe, that they remained but little known for many years after the stratigraphy of the Secondary and Tertiary series had been established.^ Though some of these underlying rocks had in various countries yielded abundant fossils, they had generally suffered so much from terrestrial disturbances, and their order of succession was consequently often so much obscured throughout western Europe, that they remained but little known for many years after the stratigraphy of the Secondary and Tertiary series had been established.

^ He could distinguish among them an older or Primary series, and a younger or Secondary series; and did not dispute the existence of a Tertiary series claimed by Peter Simon Pallas (1741-1811).

^ The later progress of investigation has slightly corrected and greatly amplified the tabular arrangement established by these authors in 1808, but the broad outlines of the Tertiary stratigraphy of the Paris basin remain still as Cuvier and Brongniart left them.

.At last in 1831 Murchison began to attack this terra incognita on the borders of South Wales, working into it from the Old Red Sandstone, the stratigraphical position of which was well known.^ The road from the last stop plunges down into the upper reaches of Titantothere Canyon and then climbs steeply up to the summit at Red Pass.
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.In a few years he succeeded in demonstrating the existence of a succession of formations, each distinguished by its own peculiar assemblage of organic remains which were distinct from those in any of the overlying strata.^ In a few years he succeeded in demonstrating the existence of a succession of formations, each distinguished by its own peculiar assemblage of organic remains which were distinct from those in any of the overlying strata.

^ Each " formation " is distinguished by its own peculiar assemblage of organic remains, by means of which it can be followed and recognized, even amid the crumplings and dislocations of a disturbed region.

^ During the latter half of the 19th century the most important development of stratigraphical geology was the detailed working out and application of the principle of zonal classification to the fossiliferous formations - that is, the determination of the sequence and distribution of organic remains in these formations, and the arrangement of the strata into zones, each of which is distinguished by a peculiar assemblage of fossil species (see under Part VI.).

.To these formations he gave the name of Silurian (q.v.^ To these formations he gave the name of Silurian (q.v.

). .From the key which his researches supplied, it was possible to recognize in other countries the same order of formations and the same sequence of fossils, so that, in the course of a few years, representatives of the Silurian system were found far and wide over the globe.^ From the key which his researches supplied, it was possible to recognize in other countries the same order of formations and the same sequence of fossils, so that, in the course of a few years, representatives of the Silurian system were found far and wide over the globe.

^ In a preliminary Discourse prefixed to his Recherches sur les ossemens fossiles (1821) Cuvier gave an outline of what he conceived to have been the past history of our globe, so far as he had been able to comprehend it from his investigations of the Tertiary formations of France.

^ As the order of succession among stratified rocks was first made out in Europe, and as many of the gaps in that succession were found to be widespread over the European area, the divisions which experience established for that portion of the globe came to be regarded as typical, and the names adopted for them were applied to the rocks of other and far distant regions.

.While Murchison was thus engaged, Sedgwick devoted himself to the more difficult task of unravelling the complicated structure of North Wales.^ While Murchison was thus engaged, Sedgwick devoted himself to the more difficult task of unravelling the complicated structure of North Wales .

.He eventually made out the order of the several formations there, with their vast intercalations of volcanic material.^ He eventually made out the order of the several formations there, with their vast intercalations of volcanic material.

^ Again, the same series of primeval sediments includes intercalations of fine silt, which has been deposited as regularly and intermittently there as it has been among the most recent formations.

^ It was not until after considerable progress had been made in determining the palaeontological distinctions and order of succession of the stratified formations of the earth's crust that it became possible to trace among these formations a succession of volcanic episodes which were contemporaneous with them.

.He named them the Cambrian system, and found them to contain fossils, which, however, lay for some time unexamined by him.^ He named them the Cambrian system , and found them to contain fossils, which, however, lay for some time unexamined by him.
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