Mountains: Wikis

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Mount Damavand, Iran

A mountain is a large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. The adjective montane is used to describe mountainous areas and things associated with them. The study of mountains is Orography.

Exogeology deals with planetary mountains, which in that branch of science are usually called montes (singular - mons). The highest mountain on earth is the Mount Everest (elevation 8,848 m). The highest known mountain in the Solar System is Olympus Mons on the planet Mars at 21,171 m (69,459 ft).

Contents

Definition

There is no universally-accepted definition of a mountain. Elevation, volume, relief, steepness, spacing and continuity has been used as criteria for defining a mountain.[1] In the Oxford English Dictionary a mountain is defined as "a natural elevation of the earth surface rising more or less abruptly from the surrounding level and attaining an altitude which, relatively to the adjacent elevation, is impressive or notable."[1]

In the United States, the following points of measurement have been used and taught in geography classes:[citation needed]

  • Flat to 500 feet, base to highest point - Rolling Plain
  • Highest point 501 to 999 feet above base - Hill
  • Highest point 1000 feet or more above base - Mountain

Whether a landform is called a mountain may depend on usage among the local people. The highest point in San Francisco, California, is called Mount Davidson, notwithstanding its height of 990 feet, which makes it ten feet short of the minimum for a mountain in American appellation. Similarly, Mount Scott outside Lawton, Oklahoma is only 824 feet from its base to its highest point.

Other definitions of "mountain" include:[2]

  • Height over base of at least 2,500m
  • Height over base of 1500-2500m with a slope greater than 2 degrees
  • Height over base of 1000-1500m with a slope greater than 5 degrees
  • Local (radius 7 km) elevation greater than 300m, or 300-1000m if local (radius 7 km) elevation is greater than 300m

By this definition, mountains cover 64% of Asia, 25% of Europe, 22% of South America, 17% of Australia, and 3% of Africa. As a whole, 24% of the Earth's land mass is mountainous and 10% of people live in mountainous regions.[3] Most of the world's rivers are fed from mountain sources, and more than half of humanity depends on mountains for water.[4][5]

Characteristics

High mountains, as well as those located close to the Earth's poles, reach into the colder layers of the atmosphere. They are consequently subject to glaciation, and erosion through frost action. Such processes produce the peak shape. Some of these mountains have glacial lakes, created by melting glaciers; for example, there are an estimated 3,000 glacial lakes in Bhutan. Mountains can be eroded and weathered, altering their characteristics over time.

Alps mountain view in Switzerland

Tall mountains have different climatic conditions at the top than at the base, and will thus have different life zones at different altitudes. At the highest elevations, trees cannot grow, and whatever life may be present will be of the alpine type, resembling tundra[6]. Just below the tree line, one may find subalpine forests of needleleaf trees, which can withstand cold, dry conditions.[7] In regions with dry climates, the tendency of mountains to have higher precipitation as well as lower temperatures also provides for varying conditions, which in turn lead to differing flora and fauna.[6][8] Some plants and animals found in these zones tend to become isolated since the conditions above and below a particular zone will be inhospitable and thus constrain their movements or dispersal. On the other hand, birds, being capable of flight, may take advantage of montane habitats and migrate into a region which would otherwise not provide appropriate habitat.[9] These isolated ecological systems, or microclimates, are known as sky islands.[10]

The reason mountains are colder than lowlands has to do with how the sun heats the surface of the earth. The sun's radiation is absorbed by land and sea, whence the heat then radiates into the air. The density of air decreases at higher altitudes, and with the thinning of the atmosphere, the insulating effect of the air decreases, resulting in less heat retention. Thus, air temperature decreases with an increase in altitude at a general rate, called the lapse rate, of 5.5°C per 1,000 m (3°F per 3,000 ft).[11][12]

Mountains are generally less preferable for human habitation than lowlands; the weather is often harsher, and there is little level ground suitable for agriculture. At very high altitudes, there is less oxygen in the air and less protection against solar radiation (UV). Acute mountain sickness (caused by hypoxia - a lack of oxygen in the blood) affects over half of lowlanders who spend more than a few hours above 3,500 meters (11,483 ft).

Many mountains and mountain ranges throughout the world have been left in their natural state, and are today primarily used for recreation, while others are used for logging, mining, grazing, or see little use. Some mountains offer spectacular views from their summits, while others are densely wooded. Summit accessibility is affected by height, steepness, latitude, terrain, weather. Roads, lifts, or tramways affect accessibility. Hiking, backpacking, mountaineering, rock climbing, ice climbing, downhill skiing, and snowboarding are recreational activities enjoyed on mountains. Mountains that support heavy recreational use (especially downhill skiing) are often the locations of mountain resorts.

Mountains are made up of earth and rock materials. The outermost layer of the Earth or the Earth's crust is composed of six plates. When two plates move or collide each other, vast land areas are uplifted, resulting in the formation of mountains. Depending upon the geological process, as to how the mountains are formed and the mountain characteristics, there are five major types of mountains.

Fold Mountains: Fold mountains are the most common type of mountains. Examples of fold mountains are the Himalayas (Asia), the Alps (Europe). They are formed due to collision of two plates, causing folding of the Earth's crust. The fold that descends on both sides is called anticline; whereas, the fold that ascends from a common low point (on both sides) is called syncline.

Fault-Block Mountains: As the name suggests, fault mountains or fault-block mountains are formed when blocks of rock materials slide along faults in the Earth's crust. There are two types of block mountains, namely the lifted and tilted. In the former type, the mountain has two steep sides; whereas, the tilted type has one steep side and gentle sloping side. Example of fault-block mountain is the Sierra Nevada mountains (North America).

Volcanic Mountains: Volcanic mountains are formed due to volcanic eruptions, for e.g. Mount Fuji (Japan). They are formed when volcanic magma erupts and piles up on the surface of the Earth.

Dome Mountains: Dome mountains are formed when the hot magma rises from the mantle and uplifts the overlying sedimentary layer of the Earth's crust. In the process, the magma is not erupted, but it cools down and forms the core of the mountain. Example of dome mountain is the Navajo Mountain in Utah. They are called dome mountains due to their appearance that resembles dome shape.

Plateau Mountains: Plateau mountains are pseudo mountains that are formed because of erosion. An example of plateau mountain is the Catskill Mountains (New York). They usually occur near the fold mountain ranges.

There are also some mountains that are formed as a result of many forces of the Earth. Though the Rockies in North America is formed due to folding, there are mountains in the same range that are formed by faulting and doming. In nature, there is a continuous process of glaciation, soil erosion, and mechanical and chemical weathering, which altogether play a major role in altering the shape and characteristics of mountains.

Geology

Chomo Lonzo Makalu Mount Everest Tibetan Plateau Rong River Changtse Rongbuk Glacier North Face East Rongbuk Glacier North Col north ridge route Lhotse Nuptse South Col route Gyachung Kang Cho Oyu Press hyperlinks (or button to enlarge image)
The Himalayan mountain range with Mount Everest.

A mountain is usually produced by the movement of lithospheric plates, either orogenic movement or epeirogenic movement. The compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. The absolute heights of features termed mountains and hills vary greatly according to an area's terrain. The major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Two types of mountain are formed depending on how the rock reacts to the tectonic forces – block mountains or fold mountains.

Compressional forces in continental collisions may cause the compressed region to thicken, so the upper surface is forced upward. In order to balance the weight of the earth surface, much of the compressed rock is forced downward, producing deep "mountain roots" [see the Book of "Earth", Press and Siever page.413]. Mountains therefore form downward as well as upward (see isostasy). However, in some continental collisions part of one continent may simply override part of the others, crumpling in the process.

Some isolated mountains were produced by volcanoes, including many apparently small islands that reach a great height above the ocean floor.

Block mountains are created when large areas are widely broken up by faults creating large vertical displacements. This occurrence is fairly common. The uplifted blocks are block mountains or horsts. The intervening dropped blocks are termed graben: these can be small or form extensive rift valley systems. This form of landscape can be seen in East Africa, the Vosges, the Basin and Range province of Western North America and the Rhine valley. These areas often occur when the regional stress is extensional and the crust is thinned.

The mid-ocean ridges are often referred to as undersea mountain ranges due to their bathymetric prominence.

Rock that does not fault may fold, either symmetrically or asymmetrically. The upfolds are anticlines and the downfolds are synclines: in asymmetric folding there may also be recumbent and overturned folds. The Jura Mountains are an example of folding. Over time, erosion can bring about an inversion of relief: the soft upthrust rock is worn away so the anticlines are actually lower than the tougher, more compressed rock of the synclines.

Gallery

See also

Further reading

  • Fraknoi, A., Morrison, D., & Wolff, S. (2004). Voyages to the Planets. 3rd Ed. Belmont: Thomson Books/Cole.

References

  1. ^ a b Gerrard, A. J. 1990. Mountain Environments
  2. ^ Blyth, S., Groombridge, B., Lysenko, I., Miles, L. & Newton, A. (2002). "Mountain Watch". UNEP World Conservation Monitoring Centre, Cambridge, UK. http://www.unep-wcmc.org/mountains/mountain_watch/pdfs/WholeReport.pdf. Retrieved 2009-02-17. 
  3. ^ Panos (2002). "High Stakes". http://www.panos.org.uk/?lid=278. Retrieved 2009-02-17. 
  4. ^ "International Year of Freshwater 2003". http://www.wateryear2003.org/en/ev.php-URL_ID=3903&URL_DO=DO_TOPIC&URL_SECTION=201.html. Retrieved 2006-12-07. 
  5. ^ "The Mountain Institute". http://www.mountain.org/mountains/whymtns.cfm?slidepage=water. Retrieved 2006-12-07. 
  6. ^ a b "Biotic Communities of the Colorado Plateau: C. Hart Merriam and the Life Zones Concept". http://cpluhna.nau.edu/Biota/merriam.htm. Retrieved 30 January 2010. 
  7. ^ "Tree". Microsoft Encarta Reference Library 2003. Microsoft Corporation. 1993-2002. 60210-442-1635445-74407. 
  8. ^ "Mountain Environments". United Nations Environment Programme World Conservation Monitoring Centre. http://www.cityofseattle.net/parks/Environment/DiscoveryParkBirds.pdf. Retrieved 30 January 2010. 
  9. ^ Taylor, Richard Cachor (2005). A Birder's Guide to Southeastern Arizona. American Birding Association. pp. 2–4. ISBN 1-878788-22-1. 
  10. ^ Tweit, Susan J. (1992). The Great Southwest Nature Factbook. Alaska Northwest Books. pp. 138–141. ISBN 0-88240-434-2. 
  11. ^ "Temperature". Microsoft Encarta Reference Library 2003. Microsoft Corporation. 1993-2002. 60210-442-1635445-74407. 
  12. ^ "Atmosphere". Microsoft Encarta Reference Library 2003. Microsoft Corporation. 1993-2002. 60210-442-1635445-74407. 

External links

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Quotes

Up to date as of January 14, 2010

From Wikiquote

An Teallach panorama.jpg

Mountains are natural elevations of the earth's surface, distinguished from hills by their greater height, and commonly by their steeper slopes and more sharply defined summits.

Sourced

All that expands the spirit, yet appals.
  • Above me are the Alps,
    The palaces of Nature, whose vast walls
    Have pinnacled in clouds their snowy scalps,
    And throned Eternity in icy halls
    Of cold sublimity, where forms and falls
    The avalanche – the thunderbolt of snow!
    All that expands the spirit, yet appals,
    Gather around these summits, as to show
    How Earth may pierce to Heaven, yet leave vain man below.
  • A man can hardly be a beast or a fool alone on a great mountain.
'Tis distance lends enchantment to the view,
And robes the mountain in its azure hue.
  • At summer eve, when Heaven's ethereal bow
    Spans with bright arch the glittering hills below,
    Why to yon mountain turns the musing eye,
    Whose sunbright summit mingles with the sky?
    Why do those cliffs of shadowy tint appear
    More sweet than all the landscape smiling near?
    'Tis distance lends enchantment to the view,
    And robes the mountain in its azure hue.
  • Auf den Bergen ist Freiheit! Der Hauch der Grüfte
    Steigt nicht hinauf in die reinen Lüfte;
    Die Welt ist vollkommen überall,
    Wo der Mensch nicht hinkommt mit seiner Qual.
    • On the mountains is freedom; no clammy breath
      Mounts there from the rotting caves of death!
      Blest is the wide world every where
      When man and his sorrows come not near.
    • Friedrich Schiller The Bride of Messina (1804), Act IV, sc. vii; translation by George Irvine (1837) p. 136.
  • Because it's there.
    • George Mallory, interviewed by the New York Times, March 18, 1923.
    • On being asked his reasons for making an attempt on Mount Everest.
  • It's a round trip. Getting to the summit is optional, getting down is mandatory.
    • Ed Viesturs No Shortcuts To The Top: Climbing the World's 14 Highest Peaks
  • Mountains are not fair or unfair, they are just dangerous.
  • Come down, O maid, from yonder mountain height,
    What pleasure lives in height (the shepherd sang)
    In height and cold, the splendour of the hills?
Great things are done when men and mountains meet.
  • Great things are done when Men & Mountains meet
    This is not Done by Jostling in the Street.
  • He who first met the Highlands' swelling blue
    Will love each peak that shows a kindred hue,
    Hail in each crag a friend's familiar face,
    And clasp the mountain in his mind's embrace.
    • Lord Byron The Island (1823), Canto II, stanza 12.
  • I demens et saevas curre per Alpes,
    ut pueris placeas et declamation fias!
    • Go, climb the rugged Alps, ambitious fool,
      To please the boys, and be a theme at school.
    • Juvenal Satires, X, line 166. Translation by John Dryden (1692), line 171.
I keep a mountain anchored off eastward a little way, which I ascend in my dreams.
  • I keep a mountain anchored off eastward a little way, which I ascend in my dreams both awake and asleep. Its broad base spreads over a village or two, which does not know it; neither does it know them, nor do I when I ascend it. I can see its general outline as plainly now in my mind as that of Wachusett. I do not invent in the least, but state exactly what I see. I find that I go up it when I am light-footed and earnest. It ever smokes like an altar with its sacrifice. I am not aware that a single villager frequents it or knows of it. I keep this mountain to ride instead of a horse.
  • In our little journey up to the Grande Chartreuse, I do not remember to have gone ten paces without an exclamation, that there was no restraining: Not a precipice, not a torrent, not a cliff, but is pregnant with religion and poetry.
    • Thomas Gray, Letter to Richard West, November 16, 1739.
  • I remember at Chamouni – in the very eyes of Mont Blanc – hearing another woman – English also – exclaim to her party – "did you ever see any thing more rural".
    • Lord Byron, Journal entry for September 17, 1816.
  • Mountains are the beginning and the end of all natural scenery.
    • John Ruskin Modern Painters (1856) Vol. 4, part 5, ch. 2.
  • There aren't four seasons a year in the mountains; there are forty seasons a day up there in those divine altitudes!
  • Petrus Comestor saith that Mount Olympus riseth even to the clear aether, wherefore letters written in the dust on the summit of that mountain have been found unchanged after the lapse of a whole year. Neither can birds live there, by reason of the rarefaction of the air, nor could the Philosophers who have ascended it remain there even for a brief space of time, without sponges soaked in water, which they applied to their nostrils and sucked thence a denser air.
Hills peep o’er Hills, and Alps on Alps arise!
  • So pleas'd at first, the towring Alps we try,
    Mount o'er the Vales, and seem to tread the Sky;
    Th' Eternal Snows appear already past,
    And the first Clouds and Mountains seem the last:
    But those attain'd, we tremble to survey
    The growing Labours of the lengthen'd Way,
    Th' increasing Prospect tires our wandring Eyes,
    Hills peep o'er Hills, and Alps on Alps arise!
  • So the loud torrent, and the whirlwind's roar,
    But bind him to his native mountains more.
The tops of mountains are among the unfinished parts of the globe, whither it is a slight insult to the gods to climb.
  • The tops of mountains are among the unfinished parts of the globe, whither it is a slight insult to the gods to climb and pry into their secrets, and try their effect on our humanity. Only daring and insolent men, perchance, go there. Simple races, as savages, do not climb mountains - their tops are sacred and mysterious tracts never visited by them.
    • Henry David Thoreau "Ktaadn" (1848), in The Maine Woods (2004) p. 65.
  • Thou hast a voice, great Mountain, to repeal
    Large codes of fraud and woe.
  • Woher kommen die höchsten Berge? so fragte ich einst. Da lernte ich, daß sie aus dem Meere kommen. Dies Zeugnis ist in ihr Gestein geschrieben und in die Wände ihrer Gipfel. Aus dem Tiefsten muß das Höchste zu seiner Höhe kommen.
    • Where do the highest mountains come from? I once asked. Then I learned that they come from out of the sea. The evidence is inscribed in their stone and in the walls of their summits. It is from the deepest that the highest must come to its height.
    • Friedrich Nietzsche Also Spracht Zarathustra (1883-91), Part III, Chapter 45. Translation by Graham Parkes, Thus Spoke Zarathustra (2005) p. 132.
You must ascend a mountain to learn your relation to matter.
  • You must ascend a mountain to learn your relation to matter, and so to your own body, for it is at home there, though you are not.
    • Henry David Thoreau, Letter to Harrison Blake, November 16, 1857.
  • A few hours mountain climbing turns a rogue and a saint into two roughly equal creatures. Weariness is the shortest path to equality and fraternity—and liberty is finally added by sleep.
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