Krakatoa

Krakatoa (), also transcribed Krakatau (), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group (Krakatoa archipelago) comprising four islands. Two of them are known as Lang and Verlaten; another, Rakata, is the only remnant of an island, also called Krakatoa, mostly destroyed by an eruption in 1883 which created the caldera.

In 1927, a fourth island, Anak Krakatoa, or "Child of Krakatoa", emerged from the caldera formed in 1883. There has been new eruptive activity since the late 20th century, with a large collapse causing the 2018 Sunda Strait tsunami. A new cinder cone eventually grew out of its collapse scar from eruptions in the 2020s.

Historical significance

The most notable eruptions of Krakatoa culminated in a series of massive explosions over 26–27 August 1883, which were among the most violent volcanic events in recorded history.

With an estimated Volcanic explosivity index (VEI) of 6, 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) dropped on Hiroshima, Japan, during World War II, and four times the yield of Tsar Bomba, the most powerful nuclear device ever detonated at 50 Mt.

The 1883 eruption ejected approximately 25 km³ (6 cubic miles) of rock. The cataclysmic explosion was heard 3,600 km (2,200 mi) away in Alice Springs, Australia, and on the island of Rodrigues near Mauritius, 4,780 km (2,970 mi) to the west.

According to the official records of the Dutch East Indies colony, 165 villages and towns were destroyed near Krakatoa, and 132 were seriously damaged. At least 36,417 people died, and many more thousands were injured, mostly from the tsunamis that followed the explosion. The eruption destroyed two-thirds of the island of Krakatoa.

Eruptions in the area since 1927 have built a new island at the same location, named Anak Krakatau (which is Indonesian for "Child of Krakatoa"). Periodic eruptions have continued since, with recent eruptions in 2009, 2010, 2011, and 2012, and a major collapse in 2018. In late 2011, this island had a radius of roughly 2 kilometres (1.2 mi), and a highest point of about 324 metres (1,063 ft) above sea level, growing five metres (16 ft) each year. In 2017, the height of Anak Krakatau was reported as over 400 m (1,300 ft) above sea level; following a collapse in December 2018, the height was reduced to 110 meters (361 ft).

Etymology

One of the earliest mentions of the name Krakatoa is in the Old Sundanese text Bujangga Manik, which was probably written in western Java in the late 15th century. Here Krakatoa is referred to as "the island of Rakata, a mountain in the middle of the sea" (pulo Rakata gunung ti tengah sagara, f. 27v). Although there are earlier descriptions in European sources 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 labelled the island "Pulo Carcata" (pulo is the Sundanese 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 Schouten, 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:

• From Sanskrit karka or karkaṭa or karkaṭaka, meaning "lobster" or "crab". The abbreviated form rakaṭa also means "crab" in the Old Javanese language. The fact that the earliest recorded mentions of the word closely resemble the pronunciation of these words for crab (rakata in Bujangga Manik and carcata in Waghenaer's map) makes this Sanskrit etymology the most likely origin of the word.
• 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, on the other side of the Wallace Line).
• 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.

The Smithsonian Institution's Global Volcanism Program cites the Indonesian name, Krakatau, as the correct name, but says that Krakatoa is often employed.

Geographical setting

Indonesia has over 130 active volcanoes, the most of any nation. They make up the axis of the Indonesian island arc system 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 Strait located at a bend in the axis of the island arc. Krakatau is directly above the subduction zone of the Eurasian Plate and the Indo-Australian Plate where the plate boundaries make a sharp change of direction, possibly resulting in an unusually weak crust in the region.

Pre-1883 history

At some point in prehistory, an earlier caldera-forming eruption had occurred, leaving as remnants Verlaten (or Sertung); Lang (also known as Rakata Kecil, or Panjang); Poolsche Hoed ("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. At the time of the 1883 eruption, the Krakatoa group comprised Lang, Verlaten, and Krakatoa itself, an island 9 km (5.6 mi) long by 5 km (3.1 mi) wide. There were also the tree-covered islet near Lang (Poolsche Hoed) and several small rocky islets or banks between Krakatoa and Verlaten.

There were three volcanic cones on Krakatoa island: Rakata, (820 m or 2,690 ft) to the south; Danan, (450 m or 1,480 ft) near the center; and Perboewatan, (120 m or 390 ft) to the north.

AD 416 event

The Javanese Book of Kings (Pustaka Raja), a 19th-century compilation of historical traditions from Central Java, records that in the year 338 Śaka (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 [(Banten) 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 ... The water subsided but the land on which Kapi stood became sea, and Java and Sumatra were divided into two parts.

The Pustaka Raja does not draw on primary sources for its description of this event, and its historical reliability is highly dubious. It is therefore impossible to verify its description of this eruption. There is no geological evidence presented that substantiates this eruption. David Keys, Ken Wohletz, and others have postulated that a violent volcanic eruption, possibly of Krakatoa, in 535 was responsible for the global climate changes of 535–536. Drilling projects in Sunda Strait ruled out any possibility that an eruption took place in 535 AD.

Middle Ages

Thornton 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 having occurred in 850, 950, 1050, 1150, 1320, and 1530.

1680

In February 1681, Johann Wilhelm Vogel, a Dutch mining engineer at Salida, Sumatra (near Padang), on his way to Batavia (now Jakarta) passed through the Sunda Strait. In his diary he wrote: