Saturday 13 July 2013

Eruption on Suwanosejima.

The Tokyo Volcanic Ash Advisory Center reported that a 1.5 km ash plume was sighted over Suwanosejima on 3 July 2013. Such events are frequent on Suwanosejima, a sparsely inhabited 8 km volcanic island in the Tokara Archipelago, though it is the first such event observed this year. The volcano is one of Japan's most active, and has caused the island to be abandoned on a number of occasions.

A smaller column over Suwanosejima in April 2011. Wikimeda Commons.

Suwanosejima is essentially a single giant stratovolcano, with four craters arranged in a line from the centre of the island, nine kilometers southwest to within a kilometer of the sea. The northeasternmost of these craters is the highest, at 799 m, and the most active, though there are occasional eruptions from the other craters. The island is about 200 km south of Kagoshima, mainland Japan's most southerly city, and has a population of about 50, including a commune run by the Buzuko counter-culture group. 

The Tokara Archipelago form part of the Ryukyu Island Arc, which sits on top of the boundary between the Eurasian and Philippine Plates. The Philippine Plate is being subducted beneath the Eurasian Plate, in the Ryukyo Trench, to the Southeast of the Islands. As it is drawn into the interior of the Earth, the tectonic plate is partially melted by the heat of the Earth's interior, and liquid magma rises up through the overlying Eurasian Plate to form the volcanos of the Ryukyu Islands and Kyushu.

The location of Suwanosejima. Google Maps.

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