Krakatoa (Indonesian: 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. The island exploded in 1883, killing approximately 40,000 people, although some estimates put the death toll much higher. The explosion is considered to be the loudest sound ever heard in modern history, with reports of it being heard nearly 3,000 miles (4,800 km) from its point of origin. The shock wave from the explosion was recorded on barographs around the globe.
Historical significance
Further information: 1883 eruption of Krakatoa
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 km3 (5.0 cu mi) of rock, ash, and pumice.[4]
The cataclysmic explosion was faintly 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 Krakatoa, according to official records, 165 villages and towns were destroyed and 132 seriously damaged, at least 21,007 (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 (which is Indonesian for "Child of Krakatoa"). This island currently[when?] has a radius of roughly 2 kilometres (1.2 mi) and a high point around 324 metres (1,063 ft) above sea level [6], growing 5 metres (16 ft) each year.[7]
Etymology and orthography
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[by whom?] the most likely origin.[citation needed]
- 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 enggak tahu)—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.
Geographical setting
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/2,690 ft) to the south; Danan, (450 m/1,480 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[10] ... 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.[11]
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.[11] 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).
1680
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 Krakatoa, 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 travellers, 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 orangutans ], and then still north of the island of Krakatou, 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 something 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-travelled 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 travellers 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 17th century 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 3,000.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.[12]:9
The 1883 eruption
Main article: 1883 eruption of Krakatoa
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.[12] Ash was propelled to a height of 80 km (50 mi). The sound of the eruption was so loud it was said that if one was within ten miles (16 km), they would go deaf.
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
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 or 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.-
A closer look at Anak Krakatau.
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Volcanic activity at Anak Krakatau.
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The thick brown plume of ash, steam and volcanic gas rising from Anak Krakatau in this true-colour satellite image is a common sight at the volcano.
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 meters 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 eruption in April 2008 saw hot gases, rocks, and lava released. Scientists monitoring the volcano have warned people to stay out of a 3 km zone around the island.[13] There are several videos of Krakatoa uploaded onto YouTube showing recent footage of it erupting[14] and inside its crater filmed at the edge of the volcano rim.[15]
On 6 May 2009 the Volcanological Survey of Indonesia raised the eruption alert status of Anak Krakatau to Level Orange.[16]
James Reynolds posted footage to YouTube[17] from as recently as November 1, 2010 showing some spectacular eruptions, and NASA has released satellite imagery[18] of the recent activity.
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An eruption in Summer 1999.
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An eruption in 2008.
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