Krakatoa

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Template:Mtnbox start norange Template:Mtnbox coor dms Template:Mtnbox volcano Template:Mtnbox finish Krakatoa (Indonesian name: Krakatau) is a volcano near the Indonesian island of Rakata in the Sunda Strait. It has erupted repeatedly, massively and with disastrous consequences throughout recorded 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 generated the loudest sound ever historically recorded by human beings — the cataclysmic explosion was distinctly heard as far away as Perth in Australia (Approx. 3100 km), and the island of Rodrigues near Mauritius (Approx. 4800 km). Atmospheric shock waves reverberated around the world seven times and were felt for five days. Near Krakatoa, according to official records, 165 villages and towns were destroyed and 132 seriously damaged, 36,419 people died, and many thousands were injured by the eruption, mostly in the tsunami which followed the explosion.

The eruption destroyed two-thirds of the pre-existing 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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Origin and spelling of the name

The earliest mention of the island in the Western world was on a map by Lucas Janszoon Waghenaer, who labelled the island "Pulo Carcata." ("Pulo" is a form of pulau, the Indonesian word for "island".) There are two spellings, Krakatoa and Krakatau, that are both acceptable. While "Krakatoa" is more common, Krakatau tends to be favored by Indonesians. The origin of the 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. The colonial Dutch, however, used the spelling Krakatowa, probably to make the Dutch pronunciation more accurate.

Theories as to the origin of the Indonesian name Krakatau include:

There exists a popular belief that Krakatau was the result of a linguistic error. According to legend, "Krakatau" was adopted when a visiting ship's captain asked a local inhabitant the island's name, and the latter replied "Kaga tau" — a Jakartan/Betawinese slang phrase meaning "I don't know". This story is largely discounted; it closely resembles famous linguistic myths about the origin of the word kangaroo and the name of the Yucatán Peninsula.

The name is spelled "Karata" on a map drawn prior to 1708.

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Before 1883

Prior to the 1883 eruption, Krakatoa consisted of three main islands: Lang ('Long', now called Rakata Kekil) and Verlaten ('Forsaken' or 'Deserted', now Sertung), which were edge remnants left from an ancient, very large caldera-forming eruption; and Krakatoa itself, an island 9 km long by 5 km wide. In addition, there was a tree-covered islet near Lang named Polish Hat (apparently because it looked like one from the sea), and several small rocks or banks between Krakatoa and Verlaten. Three volcanic cones were located on Krakatoa- running South to North they were: Rakata (823m), Danan (445m), and Perboewatan (122m). (Danan may have been a twin volcano). The volcano lies directly above the subduction zone of the Eurasian Plate and Indo-Australian Plate, at a point where the plate boundaries undertake a sharp change of direction, possibly resulting in an unusually weak crust in the region.

The Javanese Book of Kings records that in the year 338 Saka (416 AD) "A thundering sound was heard from the mountain Batuwara. [perhaps Pulosari] There was a similar noise from Kapi, west of Bantam [the north end of Java]. From it a great sheet of fire reached the sky. The whole world was shaken with violent thunderings that were accompanied by heavy rains of stones. The noise was fearful. With a tremendous roar Kapi burst into pieces and sank into the depths of the earth. The sea rose and inundated the land; its inhabitants drowned. 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 that previously joined Java to Sumatra across what is now the narrow east end of the Sunda Strait, or it may be a mistaken date, and actually refers to an eruption in 535 AD, for which there is geological evidence.

David Keys and others have postulated that a previous, even more violent eruption of Krakatoa may have been responsible for the global climate changes of 535-536. Additionally, in recent times, it has been argued that it was this eruption which created the islands of Verlaten and Lang (remnants of the original) and the beginnings of Rakata — all indicators of early Krakatoa's caldera size. However, there seems to be little, if any, datable charcoal from that eruption, even if there is plenty of circumstantial evidence.

There are reports that Danan and Perboewatan were seen erupting in May 1680 and February 1681.

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The 1883 eruption

In the years preceding the 1883 eruption, seismic activity around the volcano was intense, with some earthquakes felt as far distant as Australia. Beginning 20 May 1883, three months before the final explosion, steam venting began to occur on a regular basis from one of the island's three cones. Eruptions of ash reached an altitude of 6 km and explosions could be heard in Batavia (Jakarta) 160 km away. However, it died down by the end of May.

The volcano began erupting again on 19 June. The seat of the eruption is believed to have been a new vent or multiple vents which formed between Perboewatan and Danan, more or less where the current volcanic cone of Anak Krakatau is to be found. The violence of the eruption caused tides in the vicinity to be unusually high, and ships at anchor had to be moored with chains as a result. 11 August saw the onset of larger eruptions, with ashy plumes being emitted from as many as eleven vents. On 24 August, eruptions further intensified. At about 1pm (local time) on 26 August, the volcano went into its paroxysmal phase, and by 2pm observers could see a black cloud of ash 27 km (17 miles) high. At this point, the eruption was virtually continuous and explosions could be heard every ten minutes or so. Ships within 20 km (14 miles) of the volcano reported heavy ash fall, with pieces of hot pumice up to 10cm in diameter landing on their decks. A small tsunami hit the shores of Java and Sumatra some 40 km (28 miles) away between 6pm and 7pm.

On 27 August, the volcano entered the final cataclysmic stage of its eruption. Four enormous explosions took place at 5.30am, 6.42am, 8.20am, and 10.02am. Each was accompanied by very large tsunamis believed to have been over 100ft high in places. A large area of the Sunda Strait and a number of locations on the Sumatran coast were also affected by pyroclastic flows from the volcano. The explosions were so violent that they were heard 2,200 miles (3,500 km) away in Australia and the island of Rodrigues, near Mauritius, 4,800 km away; the sound of Krakatoa's destruction is believed to be the loudest sound in recorded history, reaching levels of 180 dBSPL 100 miles (160 km) away. Ash was propelled to a height of 50 miles (80 km). The eruptions diminished rapidly after that point and by the morning of August 28, the volcano was quiet. Small eruptions continued in the following months and in February 1884. In the aftermath of the eruption, it was found that the island of Krakatoa had almost entirely disappeared, leaving behind a 250m-deep caldera.

The combined effects of pyroclastic flows, volcanic ashes and tsunamis had disastrous results in the region. There were no survivors from 3,000 people located at the island of Sebesi, about 13 km from Krakatoa. Pyroclastic flows killed around 1,000 people at Ketimbang, located on the coast of Sumatra some 40 km north from Krakatoa. The official death toll recorded by the Dutch authorities was 36,417 and many settlements were destroyed, including Teluk Betung and Ketimbang in Sumatra, and Sirik and Semarang in Java. The areas of Bantam on Java and the Lampongs on Sumatra were devastated. Ships as far away as South Africa rocked as tsunamis hit them, and the bodies of victims were found floating in the ocean for weeks after the event. 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. Some land on Java was never repopulated; instead, it reverted to jungle and is now the Ujung Kulon National Park.

The 1883 eruption of Krakatoa is among the most violent volcanic events in modern times (a VEI of 6, equivalent to 200 megatons of TNT - about thirteen thousand times the yield of the Little Boy bomb which devastated Hiroshima, Japan. (Little Boy was officially recorded at "only" 15 kilotons. In contrast, the biggest bomb ever exploded by man, the Tsar Bomba, had an explosive power of 57 megatons.) Concussive air waves from the explosions travelled seven times around the world, and the sky was darkened for days afterwards. Waves from the tsunamis were recorded as far away as the English Channel.

The tsunamis that accompanied the eruption are believed to have been caused by gigantic pyroclastic flows entering the sea; each of the five great explosions was accompanied by a massive pyroclastic flow resulting from the gravitational collapse of the eruption column. This caused several km³ of material to enter the sea, displacing an equally huge volume of seawater. Some of the pyroclastic flows reached the Sumatran coast as much as 25 miles (40 km) away, having apparently moved across the water on a "cushion" of superheated steam. There are also indications of submarine pyroclastic flows reaching as far as 10 miles (15km) from the volcano.

As a result of the huge amount of material deposited by the volcano, the surrounding ocean floor was drastically altered. It is estimated that as much as 18-21 cubic km of ignimbrite was deposited over an area of 1.1 million square km, largely filling the 30-40m deep basin around Krakatoa. The land masses of Verlaten and Lang were increased, and volcanic ash continues to be a significant part of the geological composition of these islands. Polish Hat disappeared. A new rock islet called Bootsmansrots ('Black Man's Rock')- a fragment of Danan - was left. Two nearby sandbanks (called Steers and Calmeyer) were built up into islands by ashfall, but the sea later washed them away.

The fate of Krakatoa itself has been the subject of some dispute among geologists. It was originally proposed that the island had been blown apart by the force of the eruption. However, most of the material deposited by the volcano is clearly magmatic in origin and the caldera formed by the eruption is not extensively filled with deposits from the 1883 eruption. This indicates that the island subsided into an empty magma chamber at the end of the eruption sequence, rather than having been destroyed during the eruptions.

The violence of the final explosions has also attracted debate. Contemporary investigators believed that the volcano's vents had sunk below sea level on the morning of 27 August, permitting seawater to flood into it and causing a massive series of phreatic explosions. Alternatively the seawater could have chilled the magma, causing it to crust over and producing a "pressure cooker" effect relieved only when explosive pressures were reached. Both of these ideas assumed that the island had subsided before the explosions; however, the evidence does not support that conclusion and the pumice and ignimbrite deposits are not of a kind consistent with a magma-seawater interaction.

It has also been suggested that the final explosions may have been caused by magma mixing caused by a sudden infusion of hot basaltic magma into the cooler and lighter magma in the chamber below the volcano. This would have resulted in a rapid and unsustainable increase in pressure, leading to a cataclysmic explosion. Evidence for this theory is the existence of pumice consisting of light and dark material, the dark material being of much hotter origin. However, such material reportedly consists of less than 5% of the content of the Krakatoa ignimbrite and some investigators have rejected this as a prime cause of the 27 August explosions.

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Long-term effects

The eruption produced erratic weather and spectacular sunsets throughout the world for many months afterwards, as a result of sunlight reflected from suspended dust particles ejected by the volcano high into Earth's atmosphere. This worldwide volcanic dust veil acted as a solar radiation filter, reducing the amount of sunlight reaching the surface of the earth. In the year following the eruption, global temperatures were lowered by as much as 1.2 degrees Celsius on average. Weather patterns continued to be chaotic for years, and temperatures did not return to normal until 1888. British artist William Ashcroft made thousands of color sketches of the red sunsets half-way around the world from Krakatoa in the years after the eruption. In 2004, researchers proposed the idea that the blood-red sky shown in Edvard Munch's famous 1893 painting The Scream is also an accurate depiction of the sky over Norway after the eruption.

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Subsequent volcanism

Since the 1883 eruption, a new island volcano, called Anak Krakatau ("Child of Krakatoa"), has formed in the caldera. Of considerable interest to volcanologists, this has been the subject of extensive study since 1960. Additionally, it has also been a case study of island biogeography and founder populations in an ecosystem being built from the ground up, virtually sterilized, certainly with no macroscopic life surviving the explosion. 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 eruptions, with occasional much larger explosions. Since the 1950s, the island has grown at an average rate of five inches (13 cm) per week. Reports in 2005 indicated that activity at Anak Krakatau was increasing.

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Media

The volcano has inspired several books and films.

  • The novel Krakatit (1924, ISBN 0685513386) by Czech writer Karel Čapek, dealing with lethal menace of a fictional explosive, was inspired by the name of the volcano.
  • Krakatoa, a short 1933 movie about the volcano that won the Academy Award for Best Short Subject, Novelty for its producer Joe Rock. This movie was notable for overwhelming the sound systems of the cinemas of the time. In Australia, the distributors insisted on a power output of 10 watts RMS as a minimum for cinemas wishing to show the movie. This was then considered a large system, and forced many cinemas to upgrade.
  • Krakatoa is the location of Professor William Waterman Sherman's adventures in the book The Twenty-One Balloons (1947, ISBN 0140320970) by William Pène du Bois, which won the Newbery Medal in 1948.
  • In the TV series Time Tunnel, the episode "The Crack of Doom" aired on 14 October 1966.
  • The eruption is the subject of a 1969 Hollywood film starring Maximilian Schell, which was titled Krakatoa, East of Java — even though Krakatoa is in fact west of Java. This blatant error is perhaps the most remembered thing about the film. (Tambora, on Sumbawa, is the violent volcano east of Java).
  • Simon Winchester explores the eruption of Krakatoa in his book Krakatoa: The Day the World Exploded, 27 August 1883. (2003, ISBN 0066212855). The book examines the history of the region, the early spice trade, the growth of colonial governments, explains the geology of volcanos and describes in detail the series of eruptions and tsunamis and their effects around the globe.
  • The name of the living island Krakoa which battled the new X-Men called together by Professor X in Giant-Size X-Men #1 is obviously derived from the real Krakatoa.
  • In the television series Doctor Who, the Third Doctor implied that he had heard the sound of the eruption — or possibly that of the creatures known as the Primords — sometime prior to the serial Inferno. In the episode Rose, a sketch dated 1883 was said to have washed ashore following the eruption; it showed the Ninth Doctor in front of the volcano.
  • In Chapter 3 of Don Rosa's Life and Times of Scrooge McDuck, Scrooge McDuck rides out the tsunami from the eruption of Krakatoa.
  • Ultimate Blast: Eruption at Krakatau Template:Sic has been aired on Discovery Channel, as part of the Moments in Time series.
  • In the Spongebob Squarepants episode "Mermaidman and Barnacleboy 5," Squidward is "Captain Magma". He says "Krakatoa" before lava spews out of the volcano shaped helmet.
  • Fantasy author Graham Edwards' Stone trilogy (made up of Stone and Sky [1999], Stone and Sea [2000] and Stone and Sun [2001]) begins with the eruption of Krakatoa, which becomes the catalyst for the events that befall the main character Jonah Lightfoot and his companion Annie West. The force of the eruption blasts the two into a mysterious world called Amara. Volcanic eruption in general becomes a device later used when the eruption of Mount St. Helens in 1980 sends another person from our world into Amara.
  • In the 1996 SNES game Donkey Kong Country 3: Dixie Kong's Double Trouble!, the lost world of that game is a volcanic island by the name of "Krematoa," an obvious nod to the real-life Krakatoa. In addition, the Brothers Bear that lives in Krematoa, Boomer, specializes in bombs, spoofing the original Krakatoa's explosive nature.
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See also

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References

  • Furneaux, Rupert (1964) Krakatoa
  • Self, S. and Rampino, M.R. "The 1883 eruption of Krakatau", Nature Vol. 294, 24/31 December 1981
  • Symons, G.J. (ed) The Eruption of Krakatoa and Subsequent Phenomena (Report of the Krakatoa Committee of the Royal Society). London, 1888
  • Verbeek, R.D.M. Nature 30, 10-15 (1884)
  • Verbeek, R.D.M. Krakatau. Batavia, 1886
  • {{cite book 
| last = Winchester | first =  Simon
| title = Krakatoa: The Day the World Exploded, 27 August1883
| publisher = HarperCollins
| year = 2003
| id = ISBN 0066212855
}}
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External links

da:Krakatau de:Krakatau es:Krakatoa fi:Krakatau fr:Krakatoa he:קרקטואה id:Krakatau it:Krakatoa ja:クラカタウ nl:Krakatau no:Krakatau pl:Krakatau pt:Ilha de Krakatoa ru:Кракатау sv:Krakataus utbrott 1883 uk:Кракатау zh:喀拉喀托火山

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