Jump to content

Krakatoa

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 68.238.82.34 (talk) at 15:13, 27 May 2006. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Krakatoa
Highest point
Elevation813 m (2,667 ft) Edit this on Wikidata
Prominence813 m (2,667 ft) Edit this on Wikidata
Isolation21.71 km (13.49 mi) Edit this on Wikidata

Krakatoa (Indonesian name: Krakatau) is a volcanic island in the Sunda Strait between 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. 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 reported — the cataclysmic explosion was distinctly heard as far away as Perth in Australia (Approx. 3100 km/1900 mi), and the island of Rodrigues near Mauritius (Approx. 4800 km/3000 mi). 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, at least 36,417 (official toll) people died, and many thousands were injured by the eruption, mostly in the tsunamis 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).

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 generally accepted spellings, Krakatoa and Krakatau. While "Krakatoa" is more common in the English-speaking world, 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.

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

There is a popular story 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 before 1708.

Before 1883

Before the 1883 eruption, Krakatoa consisted of 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 long by 5 km 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: running South to North they were: Rakata (823m), Danan (445m), and Perboewatan (also spelled Perbuatan) (122m). (Danan may have been a twin volcano). Krakatoa is directly above the subduction zone of the Eurasian Plate and Indo-Australian Plate, 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 (Pustaka Raja) records that in the year 338 Saka (416 CE) "A thundering sound was heard from the mountain Batuwara ... a similar noise from Kapi ... 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 Raja Basa, was inundated by the sea; the inhabitants of the northern part of the Sunda country to the mountain Raja Basa were drowned and swept away with all property[2] ... 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, referring to an eruption in 535 CE, also referred to in the Javanese Book of Kings, and for which there is geological and some corroborating historical evidence.

David Keys and others have postulated that the violent eruption 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 Modern Civilization. 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's size. However, there seems to be little, if any, datable charcoal from that eruption, even if there is plenty of circumstantial evidence.

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

In February 1780, the crew of 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.

R. D. M. Verbeek made an official survey of the islands in 1880 and published a report. This was of great help constructing what happened in 1883.

The 1883 eruption

In the years before 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 regularly from Perboewatan, the northern 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. Activity 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 vents which formed between Perboewatan and Danan, more or less where the current volcanic cone of Anak Krakatau is. 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. On 11 August larger eruptions began, with ashy plumes being emitted from at least 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 places on the Sumatran coast were 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 Krakatoa 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, except for half of the cone of Rakata cut off along a vertical cliff, 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 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; 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 13000 times the yield of the Little Boy bomb which devastated Hiroshima, Japan). 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 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 ('Bosun'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. Seawater on hot volcanic deposits on Steers and Calmeyer caused steam which some people mistook for continued eruption.

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. Theories are:-

  • Contemporary investigators believed that the volcano's vents had sunk below sea level on the morning of 27 August, letting seawater flood into it and causing a massive series of phreatic (interaction of ground water and magma) explosions.
  • 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 these ideas assumed that the island 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.
  • A massive underwater land slump or partial subsidence suddenly left the highly pressurized magma chamber wide open.
  • 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 is 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.

Worldwide 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. The area around Java is now known as Lady Bull because of its fiery nature. 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.

Subsequent volcanism

Verbeek, in his report on the eruption, predicted that any new activity would manifest itself in the region that had been between Perboewatan and Danan. This prediction came true in June, 1927 when evidence of a submarine eruption was seen in this area. 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 several later islands) was quickly eroded away by the sea; but eventually Anak Krakatoa 4 (broke water 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 since 1960. 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.

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, virtually sterilized, certainly with no macroscopic life surviving the explosion. 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.

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).
  • In the novel Songs of Distant Earth, by Science Fiction giant Arthur C. Clarke, communications with a new human colony on far away planet Thalassa are interrupted when a giant Volcano named “Krakan” erupts. “Child of Krakan”, a smaller volcano, also features in the novel. The two are obvious links to Krakatoa.
  • 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 [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.
  • The 1883 eruption is reconstructed in the BBC drama 'Krakatoa - The Last Days', first broadcast in May 2006.

See also

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. (Rogier Diederik Marius) Nature 30, 10-15 (1884)
  • Verbeek, R.D.M. (Rogier Diederik Marius) Krakatau. Batavia, 1886
  • Winchester, Simon (2003). Krakatoa: The Day the World Exploded, 27 August1883. HarperCollins. ISBN 0066212855.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Krakatoa&oldid=55424377"