Krakatoa is a volcano in Indonesia that lies at the convergent boundary between the Eurasian and Indo-Australian tectonic plates. It was formed sometime within the past million years, when the two plates collided and the Indo-Australian plate began sliding under the Eurasian plate. The volcano is famous for its major eruption in 1883, which killed 36,000 people and was one of the deadliest eruptions in human history.
This eruption created tsunamis that swept along the coasts of the nearby islands of Sumatra and Java, and the explosion was so loud that it was heard more than 2,000 miles away in Australia.
Prior to the eruption in 1883, the massive Krakatoa volcano was spread out over three islands: Krakatoa, Verlaten and Lang. Perlaten and Lang Islands had been formed by two other volcanoes, Danan and Perbuwatan. However, this eruption was so violent that it destroyed most of all three volcanic cones and much of Krakatoa Island.
In 1927, a new island began to surface in between the three islands, caused by further small eruptions of Krakatoa. The name of this new island is Anak Krakatoa, which means Son of Krakatoa, and this new caldera has experienced quite frequent but fairly minor eruptions since it emerged from the ocean.