Krakatoa or Krakatau or Krakatao 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 eruption culminated in a series of massive explosions on August 26-27 1883.
The 1
883 eruption ejected more than 25 cubic kilometres 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). 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 which 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, 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 (or Krakatao in an older Portuguese based spelling) tends to be favored by Indonesians and geologists. 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 Krakatoa include:
* Onomatopoeia, imitating the noise made by cockatoos which used to inhabit the island.
* From Sanskrit karka or karkata or karkataka, meaning "lobster" or "crab".
* From Malay kelakatu, meaning "white-winged ant".
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.
Pre 1883 history
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 (823 m), Danan (445 m), and Perboewatan (also spelled Perbuatan) (122 m). (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.
416 AD event
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, also referred to in the Javanese Book of Kings, and for which there is geological and some corroborating historical evidence.
535 AD event
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 the Modern World. 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.
1600s
At least three Dutch travelers reported that Danan and Perboewatan were seen erupting in May 1680 and February 1681.
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 northernmost of the island's three cones. Eruptions of ash reached an altitude of 6 km (20,000 ft) and explosions could be heard in Batavia (Jakarta) 160 km (100 miles) away. Activity died down by the end of May. Also, to help the eruption along, water seeped into the magma chamber and created vast amounts of super-pressured steam. It had been thought Krakatoa was 3 different volcanoes, but it was actually just one with a huge magma chamber.
The volcano began erupting again around 20 July. 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 (11 nautical miles) of the volcano reported heavy ash fall, with pieces of hot pumice up to 10 cm 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.
Cataclysmic stage
On August 
27, the volcano entered the final cataclysmic stage of its eruption. Four enormous explosions took place at 5:30 a.m., 6:42 a.m., 8:20 a.m., and 10:02 a.m., the last of which was worst and loudest. Each was accompanied by very large tsunamis believed to have been over 30 meters (100 ft) 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.[4] 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.
"The Burning Ashes of Ketimbang"
Around
noon on August 27, a rain of hot ash fell around Ketimbang in Sumatra. Around a thousand people were killed, the only large number of victims killed by Krakatoa itself, and not the waves or after-effects.[5] Verbeek and later writers believe this unique event was a lateral blast or pyroclastic flow (perhaps traveling over the floating pumice rafts), similar to what happened in 1980 at Mt. St. Helens. The region of the ashfall ended to the northwest of Ketimbang, where the bulk of Sebesi Island offered protection from any horizontal surges.
After eruptions
Small eruptions continued through October, and continued to be reported through February 1884 (although any after mid October were discounted by Verbeek). In the aftermath of the eruption, it was found that the island of Krakatoa had almost entirely disappeared, except for the southern half of Rakata cone cut off along a vertical cliff, leaving behind a 250-meter-deep caldera.
Effects
The combin
ed 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 Banten on Java and the Lampung on Sumatra were devastated. 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.
Tsunamis
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. The tsunamis which 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 cubic kilometers of material to enter the sea, displacing an equally huge volume of seawater. In the town of Merak, a Tsunami 46 metres high destroyed the little town. 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 (15 km) from the volcano.
On a recent film and documentary, a research team at Kiel University of Germany conducted tests of pyroclastic flows moving over water. The tests revealed that hot ash traveled over the water on a cloud of superheated steam with the heavy matter precipitating out of the flow, shortly after initial contact with the water, to create a tsunami due to the precipitate mass.
Geographic effects
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 km³ of ignimbrite was deposited over an area of 1.1 million km², largely filling the 30-40 m 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. Poolsche Hoed ("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 after the two naval officers who investigated them) 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.
Global climate
In the year following the eruption, average global temperatures fell by as much as 1.2 degrees Celsius. Weather patterns continued to be chaotic for years, and temperatures did not return to normal until 1888. The eruption injected an unusually large amount of sulfur dioxide (SO2) gas high into the stratosphere which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfurous acid (H2SO3) concentration in high-level cirrus clouds. The resulting increase in cloud reflectivity (or albedo) would reflect more incoming light from the sun than usual, and cool the entire planet until the suspended sulfur fell to the ground as acid precipitation
Legacy of the 1883 eruption
The 1883 eruption of Krakatoa is among the most violent volcanic events in modern times (a VEI of 6, equivalent to 200 megatonnes of TNT — about 13,000 times the yield of the Little Boy bomb which devastated Hiroshima, Japan). Concussive air waves from the explosions travelled seven times around the world.[8] The sky was darkened for days afterwards. Sea waves caused by the eruption were recorded as far away as the English Channel.[9] The explosion is considered to be the loudest noise ever recorded to be heard by humans
MOUNT CRACATOA - VOLCANO TREKKING
Duration: 03 DAYS / 02 NIGHTS
Start / Finish: JAKARTA
Grade: Easy - Moderate
DAY 01: JAKARTA - CARITA BEACH
Upon arrival at Jakarta Airport, you will have drive to Carita beach on the western overcoast Jakarta.This land journey will takes 6- 7hours drive in normaly traffic road condition. Stay Overnight at simple hotel in Carita beach. (D)
DAY 02: CARITA BEACH - SERTUNG ISLAND "CAMPSITE"
Transfer to Sertung island by speedboat from Carita beach. You will enjoy cross the sunda strait for about 3 - 4 hours through the Cracatoa island. You will have stay overnight in tents at Sertung island as our campsite. (B, L, D)
DAY 03: SUMMIT MOUNT CRACATOA - CARITA BEACH - JAKARTA
On this morning, you will leave campsite by speadboat across to the opposite island of the Sertung island which "Sun of Cracatoa" situated, for trek to summit. Return to Carita beach and transfer to Jakarta. Stop at local restaurant in Carita enroute to Jakarta. (B,L)