Krakatoa: Wikis


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Krakatau (native name)
Krakatoa 01.JPG
An early 19th-century illustration of Krakatoa
Elevation 813 metres (2,667 ft)
Location Sunda Strait, Indonesia
Coordinates 6°06′07″S 105°25′23″E / 6.102°S 105.423°E / -6.102; 105.423Coordinates: 6°06′07″S 105°25′23″E / 6.102°S 105.423°E / -6.102; 105.423
Type Stratovolcano
Last eruption 2009[1]
Listing Spesial Ribu

Krakatoa (Indonesian: Krakatau), also spelled Cracatoa or Krakatau, is a volcanic island made of a'a lava[2] in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island (also called Rakata), and the volcano as a whole.


Historical significance

The best-known eruption of Krakatua culminated in a series of massive explosions on August 26–27, 1883, which was among the most violent volcanic events in modern and recorded history.

With a Volcanic Explosivity Index (VEI) of 6,[3] the eruption was equivalent to 200 megatons of TNT (840 PJ)—about 13,000 times the nuclear yield of the Little Boy bomb (13 to 16 kT) that devastated Hiroshima, Japan during World War II and four times the yield of the Tsar Bomba (50 MT), the largest nuclear device ever detonated.

The 1883 eruption ejected approximately 21 cubic kilometres (5.0 cu mi) of rock, ash, and pumice.[4]

The cataclysmic explosion was distinctly heard as far away as Perth in Western Australia, about 1,930 miles (3,110 km) away, and the island of Rodrigues near Mauritius, about 3,000 miles (5,000 km) away.[5 ]

Near Krakatua, according to official records, 165 villages and towns were destroyed and 132 seriously damaged, at least 36,417 (official toll) people died, and many thousands were injured by the eruption, mostly from the tsunamis that followed the explosion. The eruption destroyed two-thirds of the island of Krakatoa.

Eruptions at the volcano since 1927 have built a new island in the same location, named Anak Krakatau (Indonesian: "Child of Krakatoa"). This island currently has a radius of roughly 2 kilometres (1.2 mi) and a high point around 300 metres (980 ft) above sea level, growing 5 metres (16 ft) each year.[6]

Origin and spelling of the name

Although there are earlier descriptions of an island in the Sunda Strait with a "pointed mountain", the earliest mention of Krakatoa by name in the Western world was on a 1611 map by Lucas Janszoon Waghenaer, who labeled the island "Pulo Carcata". (Pulo is a form of pulau, the Indonesian word for "island".) About two dozen variants have been found, including Crackatouw, Cracatoa, and Krakatao (in an older Portuguese-based spelling). The first known appearance of the spelling Krakatau was by Wouter Schouten, who passed by "the high tree-covered island of Krakatau" in October 1658.

The origin of the Indonesian name Krakatau is uncertain. The main theories are:

  • Onomatopoeia, imitating the noise made by cockatoos (Kakatoes) which used to inhabit the island. However, Van den Berg points out that these birds are found only in the "eastern part of the archipelago" (meaning the Lesser Sundas, east of Java). (See Wallace Line).
  • From Sanskrit karka or karkata or karkataka, meaning "lobster" or "crab". (Rakata also means "crab" in the older Javan language.) This is considered the most likely origin.
  • The closest Malay word is kelakatu, meaning "white-winged ant". Furneaux points out that in pre-1883 maps, Krakatoa does somewhat resemble an ant seen from above, with Lang and Verlaten lying to the sides like wings.
The Sunda Strait
Satellite view of Krakatau Islands, 18 May 1992
A closer look at Anak Krakatau
  • Van den Berg (1884) recites a story that Krakatau was the result of a linguistic error. According to the legend, a visiting ship's captain asked a local inhabitant the island's name, and the latter replied, "Kaga tau" (Aku nggak tau)—a Jakartan/Betawinese slang phrase meaning "I don't know". This story is largely discounted; it closely resembles other linguistic myths about the origin of the word kangaroo and the name of the Yucatán Peninsula.

The Smithsonian Institution's Global Volcanism Program cites the Indonesian name, Krakatau, as the correct name but says that Krakatoa is often employed.[6] This is most likely caused by a British journalist (the result of a typographical error: the journalist swapped the 'a' and 'o' of the Portuguese spelling) who reported on the massive eruption of 1883. Also, like Egypt a couple of decades earlier, Polynesia (South Pacific) was in vogue in the late 19th century, and the Polynesian-like suffix -oa (as in Samoa) may have caught on as a result. While Krakatoa is more common in the English-speaking world, the Indonesian Krakatau tends to be favored by others, including geologists. Verbeek seems to have started the modern convention of using Krakatau for the island proper and reserving Rakata for the main cone.

Geographical setting

Indonesia has over 130 active volcanoes, the most of any nation. They make up the axis of the Indonesian island arc system, which was produced by northeastward subduction of the Indo-Australian Plate. A majority of these volcanoes lie along Indonesia's two largest islands, Java and Sumatra. These two islands are separated by the Sunda Straits, which are located at a bend in the axis of the island arc. Krakatoa is directly above the subduction zone of the Eurasian Plate and the Indo-Australian Plate where the plate boundaries make a sharp change of direction, possibly resulting in an unusually weak crust in the region.

Before the 1883 eruption, Krakatoa comprised two main islands: Lang ("long", now called Rakata Kecil, or Panjang), and Verlaten ("forsaken" or "deserted", now Sertung), which were edge remnants of a previous very large caldera-forming eruption; and Krakatoa itself, an island 9 km (5.6 mi) long by 5 km (3.1 mi) wide. Also there was a tree-covered islet near Lang named Poolsche Hoed ("Polish hat", apparently because it looked like one from the sea) and several small rocks or banks between Krakatoa and Verlaten. There were three volcanic cones on Krakatoa: Rakata, (820 m/2,700 ft) to the south; Danan, (450 m/1,500 ft) to the north; and Perboewatan, (120 m/390 ft) to the north (Danan may have been a twin volcano).

Pre-1883 history

At some point in prehistory, an earlier caldera-forming eruption occurred, leaving as remnants Verlaten, Long, Poolsche Hoed, and the base of Rakata. Later, at least two more cones (Perboewatan and Danan) formed and eventually joined with Rakata, forming the main island of Krakatoa. The dating of these events is currently unknown; the Sunda Strait was first mentioned by Arab sailors around 1100 AD.

416 AD event

The Javanese Book of Kings (Pustaka Raja) records that in the year 338 Saka (416 AD):

A thundering sound was heard from the mountain Batuwara [now called Pulosari, an extinct volcano in Bantam, the nearest to the Sunda Strait] which was answered by a similar noise from Kapi, lying westward of the modern Bantam [Bantam is the westernmost province in Java, so this seems to indicate that Krakatoa is meant]. A great glowing fire, which reached the sky, came out of the last-named mountain; the whole world was greatly shaken and violent thundering, accompanied by heavy rain and storms took place, but not only did not this heavy rain extinguish the eruption of the fire of the mountain Kapi, but augmented the fire; the noise was fearful, at last the mountain Kapi with a tremendous roar burst into pieces and sank into the deepest of the earth. The water of the sea rose and inundated the land, the country to the east of the mountain Batuwara, to the mountain Rajabasa [the most southerly volcano in Sumatra], was inundated by the sea; the inhabitants of the northern part of the Sunda country to the mountain Rajabasa were drowned and swept away with all property[7] ... The water subsided but the land on which Kapi stood became sea, and Java and Sumatra were divided into two parts.

There is no geological evidence of a Krakatoa eruption of this size around that time; it may describe loss of land which previously joined Java to Sumatra across what is now the narrow east end of the Sunda Strait; or it may be a mistaken date, referring to an eruption in 535 AD, for which there is some corroborating historical evidence.[8]

535 AD event

David Keys, Ken Wohletz, and others have postulated that a violent volcanic eruption, possibly of Krakatoa, in 535 may have been responsible for the global climate changes of 535-536.[8] Keys explores what he believes to be the radical and far-ranging global effects of just such a putative 6th-century eruption in his book Catastrophe: An Investigation into the Origins of the Modern World. Additionally, in recent times, it has been argued that it was this eruption which created the islands of Verlaten, Lang, and the beginnings of Rakata—all indicators of early Krakatoa's caldera's size. To date, however, little datable charcoal from that eruption has been found.

Thornton (p. 47) mentions that Krakatoa was known as "The Fire Mountain" during Java's Sailendra dynasty, with records of seven eruptive events between the 9th and 16th centuries. These have been tentatively dated as 850, 950, 1050, 1150, 1320, and 1530 (all AD/CE).


In February 1681, Johann Wilhelm Vogel, a Dutch mining engineer at Salida, Sumatra (near Padang), on his way to Batavia (modern Jakarta) passed through the Sunda Strait. In his diary he wrote:

...I saw with amazement that the island of Cracketovv, on my first trip to Sumatra [June 1679] completely green and healthy with trees, lay completely burnt and barren in front of our eyes and that at four locations was throwing up large chunks of fire. And when I asked the ship's Captain when the aforementioned island had erupted, he told me that this had happened in May 1680 ... He showed me a piece of pumice as big as his fist.

Vogel spent several months in Batavia, returning to Sumatra in November 1681. On the same ship were several other Dutch travelers, including Elias Hesse, who would be called a travel writer nowadays. Hesse's journal reports that on

the 19th [of November 1681] we again lifted anchor and proceeded first to the north of us to the island of Sleepzie [ Sebesi ], uninhabited, ...[here he tells of a legend about crying ghosts, which actually were orangutangs ], and then still north of the island of Cracatou, which erupted about a year ago and also is uninhabited. The rising smoke column of this island can be seen from miles away; we were with our ship very close to shore and we could see the trees sticking out high on the mountain, and which looked completely burned, but we could not see the fire itself.

Vogel returned to Amsterdam in 1688 and published the first edition of his journal in 1690.

These reports of an eruption in 1680-81 pose somewhat of a puzzle. These are the only two reports of an eruption that have been found to date, yet at the time, the Sunda Strait was one of the heaviest-traveled waterways in the world. Records for this time period are particularly detailed, because there was an intense effort to wipe out pirates that were preying on vessels in the Strait. Neither Vogel nor Hesse mention Krakatoa in any real detail in their other passings, and no other travelers at the time mention an eruption or evidence of one. (In November 1681, a pepper crop was being offered for sale.) Both Van den Berg and Verbeek conclude from this that Vogel must have exaggerated the extent of the eruption he saw. Even so, there must have been an eruption around this time, since in 1880, Verbeek investigated a fresh unweathered lava flow at the northern coast of Perboewatan, which could not have been more than a couple of centuries old.

Visit by HMS Discovery

In February 1780, the crews of HMS Resolution and HMS Discovery, on the way home after Captain James Cook's death in Hawaiʻi, stopped for a few days on Krakatoa. They found two springs on the island, one fresh water and the other hot. They described the natives who then lived on the island as "friendly" and made several sketches. (In his journal, John Ledyard calls the island "Cocoterra".)

Dutch activity

In 1620 the Dutch set up a naval station on the islands and somewhat later a shipyard was built. Sometime in the late 1600s an attempt was made to establish a pepper plantation on Krakatoa but the islands were generally ignored by Dutch colonial authorities. In 1809 a penal colony was established at an unspecified location which was in operation for about a decade. By the 1880s the islands were without permanent inhabitants; the nearest settlement was the nearby island of Sebesi (about 12 km away) with a population of about 3000.

Several surveys and charts were made, but mainly for the purpose of mariners, and the islands were little explored or studied. An 1854 map of the islands was used in an English chart, which shows some difference from a Dutch chart made in 1874. In July 1880, Rogier Verbeek made an official survey of the islands but he was only allowed to spend a few hours there. He was able to collect samples from several places and his investigation proved important in judging the geological impact of the 1883 eruption.[9]:9

The 1883 eruption

Evolution of the islands around Krakatoa (French)

While seismic activity around the volcano was intense in the years preceding the cataclysmic 1883 eruption, a series of lesser eruptions beginning in mid-June 1883 led up to the disaster. The volcano released huge plumes of steam and ash lasting until late August.

On August 27, a series of four huge explosions almost entirely destroyed the island. The explosions were so violent that they were heard 3,500 km (2,200 mi) away in Perth, Western Australia and the island of Rodrigues near Mauritius, 4,800 km (3,000 mi) away.[5 ] The pressure wave from the final explosion was recorded on barographs around the world, which continued to register it up to 5 days after the explosion. The recordings show that the shockwave from the final explosion reverberated around the globe 7 times in total.[9] Ash was propelled to a height of 80 km (50 mi).

The combined effects of pyroclastic flows, volcanic ashes, and tsunamis had disastrous results in the region. The official death toll recorded by the Dutch authorities was 36,417, although some sources put the estimate at more than 120,000. There are numerous documented reports of groups of human skeletons floating across the Indian Ocean on rafts of volcanic pumice and washing up on the east coast of Africa, up to a year after the eruption.

Average global temperatures fell by as much as 1.2 degrees Celsius in the year following the eruption. Weather patterns continued to be chaotic for years and temperatures did not return to normal until 1888.

Subsequent volcanism

Volcanic activity at Anak Krakatau
Eruption in 2008

Anak Krakatau

Verbeek, in his report on the eruption, predicted that any new activity would manifest itself in the region which had been between Perboewatan and Danan. This prediction came true on 29 December 1927, when evidence of a submarine eruption was seen in this area (an earlier event in the same area had been reported in June 1927). A new island volcano, named Anak Krakatau ("Child of Krakatoa"), rose above the waterline a few days later. The eruptions were initially of pumice and ash, and that island and the two islands that followed were quickly eroded away by the sea. Eventually a fourth island named Anak Krakatau broke water in August 1930 and produced lava flows faster than the waves could erode them. Of considerable interest to volcanologists, this has been the subject of extensive study.

Current activity

Anak Krakatau has grown at an average rate of five inches (13 cm) per week since the 1950s. This equates to an average growth of 6.8 metres per year; the island is still active, with its most recent eruptive episode having begun in 1994. Quiet periods of a few days have alternated with almost continuous Strombolian eruptions since then, with occasional much larger explosions.

The most recent eruption began in April 2008, when hot gases, rocks, and lava were released. Scientists monitoring the volcano have warned people to stay out of a 3 km zone around the island.[10]

On 6 May 2009 the Volcanological Survey of Indonesia raised the eruption alert status of Anak Krakatau to Level Orange.[11]

Biological research

The islands have become a major case study of island biogeography and founder populations in an ecosystem being built from the ground up in an environment virtually sterilized.

The islands had been little explored or surveyed before the 1883 catastrophe—only two pre-1883 biological collections are known: one of plant specimens and the other part of a shell collection. From descriptions and drawings made by the HMS Discovery, the flora appears to have been representative of a typical Javan tropical climax forest. The pre-1883 fauna is virtually unknown but was probably typical of the smaller islands in the area.

The Krakatau problem

Biologically, the Krakatau problem refers to the question of whether the islands were completely sterilized by the 1883 eruption or whether some life survived. When the first researchers reached the islands in May 1884, the only living thing they found was a spider in a crevice on the south side of Rakata. Life quickly recolonized the islands, however; Verbeek's visit in October 1884 found grass shoots already growing. The eastern side of the island has been extensively vegetated by trees and shrubs, presumably brought there as seeds washed up by ocean currents or carried in birds' droppings (or brought by natives and scientific investigators). It is, however, in a somewhat fragile position, and the vegetated area has been badly damaged by recent eruptions.

Handl's occupancy

A German, Johann Handl, obtained a permit to mine pumice in October 1916 (Thornton). His lease was for 8.7 square kilometres (3.4 sq mi), which was basically the eastern half of the island, for 30 years. He occupied the south slope of Rakata from 1915 to 1917, when he left due to "violation of the terms of the lease." (Winchester gives the date of Handl's leaving as late 1917–1921.) Handl built a house and planted a garden with "4 European families and about 30 coolies". He is also believed to have introduced Rattus rattus (Black Rat). He also found unburned wood below the 1883 ash deposits when digging, and fresh water was found below 18 feet (5.5 m).

See also



  1. ^
  2. ^ Thornton, Ian W. B. (1997). Krakatau: the destruction and reassembly of an island ecosystem. Harvard University Press. p. 183. ISBN 0674505727.  
  3. ^ Breining, Greg (2007). "The Deadliest Volcanoes". Super Volcano: The Ticking Time Bomb Beneath Yellowstone National Park. Voyageur Press. pp. 256. ISBN 978-0-7603-2925-2.  
  4. ^ The Volcano That Shook the world: Krakatoa 1883Deborah Hopkinson. Storyworks. New York: Jan 2004. Vol. 11, Iss. 4; pg. 8 from
  5. ^ a b The Independent, May 3 2006."How Krakatoa made the biggest bang."
  6. ^ a b "Krakatau". Global Volcanism Program, Smithsonian Institution.  
  7. ^
  8. ^ a b Wohletz KH, 2000, Were the Dark Ages triggered by volcano-related climate changes in the 6th century? EOS Trans Amer Geophys Union 48(890), F1305.
  9. ^ a b Symons, G.J. (ed) The Eruption of Krakatoa and Subsequent Phenomena (Report of the Krakatoa Committee of the Royal Society). London, 1888
  10. ^ Indonesia's Krakatau roars, dazzles with fireworks - Nov 11, 2007.
  11. ^ VSI Alert


  • Alfred, E. & Seward, A.C.; The New Flora of the Volcanic Island of Krakatau, (reissued by Cambridge University Press, 2009, ISBN 9781108004336)
  • Dickins, Rosie; The Children's Book of Art (An introduction to famous paintings) Usborne Publishing Ltd., Usborne House, 83-85 Saffron Hill, London ISBN 978-0-439-88981-0 (2005)
  • Furneaux, Rupert; Krakatoa Secker and Warburg, London (1965)
  • Self, Stephen & Rampino, Michael R. (1981). "The 1883 eruption of Krakatau". Nature 294: 699–704. doi:10.1038/294699a0.  
  • Simkin, Tom and Richard S. Fiske (editors); Krakatau, 1883—the volcanic eruption and its effects Smithsonian Institution Press, Washington, D.C. ISBN 0-87474-841-0 (1983)
  • Symons, G.J. (ed); The Eruption of Krakatoa and Subsequent Phenomena (Report of the Krakatoa Committee of the Royal Society) London (1888)
  • Thornton, Ian; Krakatau: The Destruction and Reassembly of an Island Ecosystem (1996)
  • Verbeek, R. D. M. (1884). "The Krakatoa eruption". Nature 30: 10–15. doi:10.1038/030010a0.  
  • Verbeek, Rogier Diederik Marius; Krakatau Batavia (1885)
  • Winchester, Simon; Krakatoa: The Day the World Exploded: August 27, 1883 HarperCollins, New York ISBN 0066212855 (2003)

External links

Travel guide

Up to date as of January 14, 2010

From Wikitravel

Krakatoa (Gunung Krakatau) is a volcanic island between Java and Sumatra in Indonesia. It is part of the Province of Lampung in Sumatra. The eruption of Mount Krakatoa in 1883 was one of the most violent volcanic events on record. A huge explosion (150 megatons of TNT) occurred as seawater hit hot magma and turned instantly to steam. The blast was heard over 4,000 km away in Australia and India. The Volcano Explosivity Index (VEI) of the eruption is 6 (colossal).

The whole volcano was destroyed because of the massive explosion. Parts of the volcano fell into the sea and caused giant tsunami (40 meters). The dust from the eruption reached the stratosphere and affected weather worldwide for several years. More than 35,000 people are killed by tsunami and eruption. Only about a third of the pre-1883 island survived the blast.

From 1927 to 1930, there were several underwater eruptions on the site of the old Krakatoa volcano. On August 11, 1930, a new volcano and island appeared. This new volcano and island are called "Anak Krakatau" (Child of Krakatoa).

The island of Anak Krakatoa is a national park. To land on the island, tourist must obtain a permit from Balai Konservasi Sumber Daya Alam (BKSDA).

Get in

You can reach Anak Krakatoa Island using boats from Anyer beach or Carita beach (Banten), or Lampung.

From Anyer and Carita

The easiest way to get in to Krakatoa is by contacting tour operators in Anyer or Carita. One is Krakatau Tours [[1]]. Anyer can be reached from Jakarta with public bus from Kalideres bus station. The range of the tour fee will be around Rp 750,000 - 3,000,0000 depend on how many people join in the tour group and also the length of the tour. The price will include food, boat, tent and guide.

From Lampung

The other way to reach Krakatau which is less famous for the foreigners but become a better choice for the locals who want to save some money is through Lampung Province. It takes more time to reach Krakatau from here but the journey is worth it if you want more adventurous way. Lampung can be reached by land or Ferry from Merak Port. The Ferry journey takes 2 hours to Rajabasa Port in Lampung. The cost is Rp 10,000. From Rajabasa bus station, you can take a yellow minibus to take you to Kalianda for around Rp 12,000. You can contact Krakatoa Nirvana Resort (62-727-322888, 322 900) who occasionally arrange trips to Krakatau. The tour cost is Rp 3,500,000 for the whole boat, including lunch and a tour guide. If you have ten people with you, it is better to get your trip from here.

The cheaper option is to get boat at Canti Port. You can reach Canti Port from Kalianda with motorcycle taxi (Ojeg) for Rp 10,000 or minibus for Rp 5,000. If you want to hire a traditional fishing boat to take you to Krakatoa, you can make a deal with the boat owner there. One day boat rental will cost you around Rp 1,500,000 (day time only). You have to bring your own life vest because the traditional fishing boat will not provide it. There is a cheaper option from Sabesi Island. Regular boats from Canti Port operate from 11:00 AM to 2:00 PM and cost Rp 15,000. If you are in the rush to Sabesi, you can hire a boat for only Rp 400,000 one way. In Sabesi Island, you can contact some fishermen there who will hire their boat. The price for the boat will be around Rp 300,000 for day time and Rp 600,000 for night time. You have to bring your own food and life vest. One of the rangers (Pak Akhyar, mobile:+6281369281861) on this island can arrange a convenient trip to Krakatau. The price will include boat, food, tend and a tour guide. He also provides the life vest. You can negotiate the price with him directly.

Beware of strong current and large waves during August, September, October, and November. Anak Krakatao is an active volcano.


Most of the tour operators in Labuan and Anyer have a camp during the night at Rakata Island. You can enjoy the eruption of Krakatoa at night from here. If you want to stay in Sabesi island, you can stay at a simple hotel which belongs to the Indonesia Tourism Board, just walking distance from Sabesi island jetty. The contact person is Pak Hayun, mobile +628187013757. The price is reasonable between Rp 200,000- Rp 300,000 per room which can accommodate 10 people in one room. The private room is little bit more expensive with TV inside but the size is smaller. The private room can only accommodate 4 people. Some people in this island also provide homestay for the travelers. The price is negotiable. If you are adventurous enough, you can try this option.

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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

KRAKATOA (KRAKATAO, KRAKATAU), a small volcanic island in Sunda Strait, between the islands of Java and Sumatra, celebrated for its eruption in 1883, one of the most stupendous, ever recorded. At some early period a large volcano rose in the centre of the tract where the Sunda Strait now runs. Long before any European had visited these waters an explosion took place by which the mountain was so completely blown away that only the outer portions of its base were left as a broken ring of islands. Subsequent eruptions gradually built up a new series of small cones within the great crater ring. Of these the most important rose to a height of 2623 ft. above the sea and formed the peak of the volcanic island of Krakatoa. But compared with the great neighbouring volcanoes of Java and Sumatra, the islets of the Sunda Strait were comparatively unknown. Krakatoa was uninhabited, and no satisfactory map or chart of it had been made. In 1680 it appears to have been in eruption, when great earthquakes took place and large quantities of pumice were ejected. But the effects of this disturbance had been so. concealed by the subsequent spread of tropical vegetation that the very occurrence of the eruption had sometimes been called in question. At last, about 1877, earthquakes began to occur frequently in the Sunda Strait and continued for the next few years. In 1883 the manifestations of subterranean commotion became more decided, for in May Krakatoa broke out in eruption. For some time the efforts of the volcano appear to have consisted mainly in the discharge of pumice and dust, with the usual accompaniment of detonations and earthquakes. But on the 26th of August a succession of paroxysmal explosions. began which lasted till the morning of the 28th. The four most violent took place on the morning of the 27th. The whole of the northern and lower portion of the island of Krakatoa, lying within the original crater ring of prehistoric times, was blown away; the northern part of the cone of Rakata almost entirely disappeared, leaving a vertical cliff which laid bare the inner structure of that volcano. Instead of the volcanic island which had previously existed, and rose from 300 to 1400 ft. above the sea, there was now left a submarine cavity, the bottom of which was here and there more than 1000 ft. below the sea-level. This prodigious evisceration was the result of successive violent explosions of the superheated vapour absorbed in the molten magma within the crust of the earth. The vigour and repetition of these explosions, it has been suggested, may have been caused by sudden inrushes of the water of the ocean as the throat of the volcano was cleared and the crater ring was lowered and ruptured. The access of large bodies of cold water to the top of the column of molten lava would probably give rise at once to some minor explosions, and then to a chilling of the surface. of the lava and a consequent temporary diminution or even cessation of the volcanic eructations. But until the pent-up water-vapour in the lava below had found relief it would only gather strength until it was able to burst through the chilled. crust and overlying water, and to hurl a vast mass of cooled lava, pumice and dust into the air.

The amount of material discharged during the two days of paroxysmal energy was enormous, though there are no satisfactory data for even approximately estimating it. A large: cavity was formed where the island had previously stood, and the sea-bottom around this crater was covered with a wide and thick sheet of fragmentary materials. Some of the surrounding islands received such a thick accumulation of ejected stones and.

dust as to bury their forests and greatly to increase the area of the land. So much was the sea filled up that a number of new islands rose above its level. But a vast body of the fine dust was carried far and wide by aerial currents, while the floating pumice was transported for many hundreds of miles on the surface of the ocean. At Batavia, too m. from the centre of eruption, the sky was darkened by the quantity of ashes borne across it, and lamps had to be used in the houses at midday. The darkness even reached as far as Bandong, a distance of nearly 150 miles. It was computed that the column of stones, dust and ashes projected from the volcano shot up into the air for a height of 17 m. or more. The finer particles coming into the higher layers of the atmosphere were diffused over a large part of the surface of the earth, and showed their presence by the brilliant sunset glows to which they gave rise. Within the tropics they were at first borne along by air-currents at an estimated rate of about 73 m. an hour from east to west, until within a period of six weeks they were diffused over nearly the whole space between the latitudes 30° N. and 45° S. Eventually they spread northwards and southwards and' were carried over North and South America, Europe, Asia, South Africa and Australasia. In the Old World they spread from the north of Scandinavia to the Cape of Good Hope.

Another remarkable result of this eruption was the world-wide disturbance of the atmosphere. The culminating paroxysm on the morning of the 27th of August gave rise to an atmospheric wave or oscillation, which, travelling outwards from the volcano as a centre, became a great circle at 180 from its point of origin, whence it continued travelling onwards and contracting till it reached a node at the antipodes to Krakatoa. It was then reflected or reproduced, travelling backwards agai,n to the volcano, whence it once more returned in its original direction.

In this manner its repetition was observed not fewer than seven times at many of the stations, four passages having been those of the wave travelling from Krakatoa, and three those of the wave travelling from its antipodes, subsequently to which its traces were lost " (Sir R. Strachey).

The actual sounds of the volcanic explosions were heard over a vast area, especially towards the west. Thus they were noticed at Rodriguez, nearly 3000 English miles away, at Bangkok (1413 m.), in the Philippine Islands (about 1450 m.), in Ceylon <2058 m.) and in West and South Australia (from 1300 to 2250 m.). On no other occasion have sound-waves ever been perceived at anything like the extreme distances to which the detonations of Krakatoa reached.

Not less manifest and far more serious were the effects of the successive explosions of the volcano upon the waters of the ocean. A succession of waves was generated which appear to have been of two kinds, long waves with periods of more than an hour, and shorter but higher waves, with irregular and much briefer intervals. The greatest disturbance, probably resulting from a combination of both kinds of waves, reached a height of about 50 ft. The destruction caused by the rush of such a body of sea-water along the coasts and low islands was enormous. All vessels lying in harbour or near the shore were stranded, the towns, villages and settlements close to the sea were either at once, or by successive inundations, entirely destroyed, and more than 36,000 human beings perished. The sea-waves travelled to vast distances from the centre of propagation. The long wave reached Cape Horn (7818 geographical miles) and possibly the English Channel (11,040 m.). The shorter waves reached Ceylon and perhaps Mauritius (2900 m.).

See R. D. M. Verbeek, Krakatau (Batavia, 1886); " The Eruption of Krakatoa and Subsequent Phenomena," Report, of the Krakatoa Committee of the Royal Society (London, 1888).

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Simple English

An early 19th century image of Krakatoa

Krakatoa (Indonesian name: Krakatau) is a volcano near the Indonesian island of Rakata in the Sunda Strait. It has erupted repeatedly in known history. The best known of these events occurred in late August 1883.

The 1883 eruption ejected more than six cubic miles (25 cubic kilometres) of rock, ash, and pumice [1], and made the loudest sound ever recorded by human beings — the sound was heard as far away as Perth in Australia (very far), and the island of Rodrigues near Mauritius (Very far). Many thousands of people were killed and injured by the eruption, mostly in the tsunami (giant wave) which followed the explosion.

The eruption destroyed two-thirds of the what was then the island of Krakatoa. New eruptions at the volcano since 1927 have built a new island, called Anak Krakatau (child of Krakatoa).

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