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Krakatoa (Indonesian name: Krakatau) is a volcano on the Indonesian island of Rakata in the Sunda Strait. It erupted repeatedly, massively and with disastrous consequences on August 26, 1883.

The eruptions occurred at 5:30 am, 6:42 am, 8:20 am and 10:02 am local time. The lattermost was the loudest and most destructive one, and could be heard from locations in Australia 2200 miles away, and even from 3000 miles away, on the island of Rodrigues near Mauritius.

They were the most severe volcanic explosions on Earth in modern times (VEI of 6, equivalent to 200 megatons of TNT). Sound waves from the explosions travelled seven times around the world. The sky was darkened for days afterwards. The island of Rakata itself largely ceased to exist, and its surrounding ocean floor was drastically altered. Two nearby islands, Verlaten and Lang, had their land masses increased. Volcanic ash continues to be a significant part of the geological composition of these islands.

There had been volcanic and seismic activity present around the island earlier that year, when an earthquake occurred. On May 20, 1883, the hitherto inert volcano erupted. By August 11, 1883, three vents were regularly erupting on the volcano. Tides continued to be unusually high, and phenonema such as windows suddenly shattering were commonplace. Ships at anchor were sometimes tied down with chains.

About 36,000 people (some sources say 36,417) were killed by the resultant tsunami waves generated. Amongst the settlements that were wiped out were Telok Batong in Sumatra, and Sirik and Semarang in Java. Bodies of victims could be found floating in the ocean for weeks after the event. An additional 1000 or so people also died from volcanic fumes and ashes.

It has been suggested that an eruption of Krakatoa may have been responsible for the 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 that early Krakatoa's caldera size, and not the long-believed eruption of approx 416 CE, for which conclusive evidence does not exist. Indeed, it has been argued by Winchester (see Sources below), that the book which chronicles this possible event, the Javanese 'Book Of Kings', completed in the 1680's, may have been embellishing the truth, or even a complete fiction.

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.

Krakatoa was the name of a short 1933 movie about the volcano which won the Academy Award for Best Short Subject, Novelty for its producer Joe Rock. This movie was also 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.

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