Monday 25 April 2022

Eruption on Anak Krakatoa produces column of ash 3 km high.

Anak Krakatoa, a volcanic island located in the Sunda Strait between Sumatra and Java, underwent a major eruption on Sunday 24 April 2022, producing a column of ash about 3 km high. The volcano had been erupting intermitantly for several weeks, but this event was significantly larger than previous eruptions in this cycle, and 24 hours after the initial eruption the Anak Krakatoa was still erupting intermitently, producing ash columns between 500 m and 3 km high. The Badan Nasional Penanggulangan Bencana has advised that people living close to the volcano wear dust masks when going outside until the volcano subsides.

An ash column over Anak Krakatoa (at the right of the image) on 24 April 2024. Dziki Oktomauliyadi/AFP.

Anak Krakatau is a volcanic island located in the Sunda Strait between Sumatra and Java. The volcano (then known simply as Krakatoa) famously exploded in 1883, killing over 36 000 people (possibly over 120 000), largely through a series of tsunamis. This explosion more-or-less completely destroyed the island, but since then a new volcano, Anak Krakatau (meaning the 'son of Krakatoa'), has grown in its place. Anak Krakatau is almost never completely quiet, but goes through periods of greater and lesser activity. An eruption on 22 December 2018 triggered a tsunami which tsunami caused over 430 fatalities, injured 14 000 people, and displaced 33 000 more along the Sunda Strait. The tsunami risk of this area is particularly high as the coast is very popular with both locals and tourists and is home to over 20 million people within a 100 km distance from the volcano.

Anak Krakatau is located to the north of the Sunda Trench, along which the Australian Plate is being subducted beneath the Sunda Plate, on which the island sits. As the Australian Plate is subducted it is partially melted by the friction and the heat of the planet's interior. Some of this melted material then rises through the overlying Sunda Plate, fuelling Krakatau and the volcanoes of Sumatra and Java.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

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