Monday 17 September 2012

Eruptions on Krakatau.

Krakatau is a volcanic island located in the Sunda Strait between Sumatra and Java. The volcano 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, sometimes called Anak Krakatau, has grown in its place.

An eruption on the new Krakatau volcano. Stromboli Online.

Anak Krakatau is almost never completely quiet, but goes through periods of greater and lesser activity.  The volcano has reportedly been obscured from casual observations for much of the time by fog since June this year (2012), but seismic activity has occasionally been recorded and small plumes noted over the island. On 2 September 2012 a sharp rise in earthquake activity was noted, followed by a Strombolian eruption in the evening that through hot (incandescent) lava 200-300 m above the crater. On 3 September NASA's Terra Satellite observed an ash-plume over the volcano, and on the fourth the Earth Observing-1 Satellite observed fresh lava-flows on the southeastern flank of the island. 

Terra Satellite image of the ash-plume from Krakatau on 3 September 2012. NASA/Earth Observatory.

Earth Observing-1 Satellite image of fresh lava on Krakatau on 4 September 2012. NASA/Earth Observatory.

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, fueling Krakatau and the volcanoes of Sumatra and Java.

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