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Krakatoa
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Krakatoa , also spelled Krakatao, is a volcanic island 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.
best-known eruption culminated in a series of massive explosions on August 26–27, 1883, which was among the most violent volcanic events in modern times.
With a Volcanic Explosivity Index of 6, the eruption was equivalent to 200 megatons of TNT—about 13,000 times the 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 of rock, ash, and pumice.
The cataclysmic explosion was distinctly heard as far away as Perth in Western Australia, about away, and the island of Rodrigues near Mauritius, about away.
Near Krakatoa, 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.
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Krakatoa , also spelled Krakatao, is a volcanic island 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
Its best-known eruption culminated in a series of massive explosions on August 26–27, 1883, which was among the most violent volcanic events in modern times.
With a Volcanic Explosivity Index of 6, the eruption was equivalent to 200 megatons of TNT—about 13,000 times the 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 of rock, ash, and pumice.
The cataclysmic explosion was distinctly heard as far away as Perth in Western Australia, about away, and the island of Rodrigues near Mauritius, about away.
Near Krakatoa, 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 and a high point around above sea level, growing each year.
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.
- 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.
There are two generally accepted modern spellings, Krakatoa and Krakatau. The origin of the English spelling Krakatoa is unclear but may have been the result of a typographical error made in a British source reporting 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 three 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 long by 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, to the south; Danan, to the north; and Perboewatan, 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, Lang, 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):
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.
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. 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. However, to date, little, if any, datable charcoal from that eruption has been found.
Thornton (p. 47) mentions that Krakatoa was known as "The Fire Mountain" during Java's Cailendra 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).
1680
In February 1681, Johann Wilheim 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:
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
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 Hawaii, 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 generally, the islands were 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 to 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.
The 1883 eruption
Subsequent volcanism
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 few days later, a new island volcano, named "Anak Krakatau" ("Child of Krakatoa"), broke water. Initially, the eruptions were of pumice and ash, and it (and two later islands) was quickly eroded away by the sea; but eventually Anak Krakatau #4 (broke water in August 1930) 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
Since the 1950s, Anak Krakatau has grown at an average rate of five inches (13 cm) per week. The island is still active, with its most recent eruptive episode having begun in 1994. Since then, quiet periods of a few days have alternated with almost continuous Strombolian eruptions, 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.
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 has 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 , 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 .
National park
After Handl's departure, the western half of Rakata and Verlaten were designated a national monument in July 1919. The eastern half was added in 1925, and the islands were included in the Ujung Kulon Reserve, which had been established in 1921. In 1982, Ujung Kulon was made a national park. This led to a political problem since the Krakatoa Islands are politically controlled by the Lampung province of Sumatra, but part of a Javan park. This paradox was resolved in 1990, when Krakatoa was made a separate nature reserve. Park rangers have a station on Sertung, from which they patrol, but as of 1996, they have no permanent patrol boats.
See also
External links
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