Krakatoa

Krakatoa (Indonesian: Krakatau), 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.

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, it 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, and four times the yield of the Tsar Bomba (50 MT), the largest nuclear weapon ever built. The 1883 eruption ejected approximately 21 cubic kilometres (5.0 cu mi) of rock, ash, and pumice, and generated the loudest sound historically reported: the cataclysmic explosion was distinctly heard as far away as Perth in Australia approx. 1,930 miles (3,110 km), and the island of Rodrigues near Mauritius approx. 3,000 miles (5,000 km) distant. 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 2 kilometres (1.2 mi) and a high point around 300 metres (980 ft) above sea level, growing 5 metres (16 ft) 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 Shouten, 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).

* From Sanskrit karka or karkata or karkataka, meaning "lobster" or "crab". ("Rakata" is also "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 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 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), 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 remmants Verlaten, Lang, Polish Hat, 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.

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 in 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 2 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 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).

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.

Credited to wikipedia and flickr:flydime