Saturday 5 October 2013

Eruption and pyroclastic flow on Sakurajima, Kyushu.

The Sakurajima Volcano, situated on an island in Kagoshima Bay, Kyushu, underwent a large explosive eruption on the morning of Friday 4 October 2013, producing a 4 km high ash column and triggering a pyroclastic flow (avalanche of hot gas and ash) on the mountain's northwest flank. This was the third such eruption so far in October this year. The volcano is currently undergoing a particularly eruptive phase, and has undergone several hundred explosive eruptions so far this year (the exact figure is hard to derive as eruptions often occur close together and may run into one another).

Webcam image of Sakurajima on the morning of 4 October 2013, taken from the east. MBC.

Japan has a complex tectonic environment with four plates underlying parts of the Islands; in addition to the Pacific in the east and the Othorsk in the North, there are the Philipine Plate to the south and the Eurasian Plate to the West. Kyushu Island lies at the northeast end 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 Mount Sakurajima on Kagoshima Island in Kagoshima Bay on the southern tip of Kyushu Island, Japan. Google Maps.

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