Friday 6 April 2018

Ongoing eruptions on Mount Shinmoedake, Japan.

Mount Shinmoedake, a 1421 m volcano that part of the Kirishima Volcanic Complex on southern Kyūshū Island, erupted again on the morning of Thursday 2 April 2018, producing a column of ash that rose over 5 km above the summit of the volcano. This was the first eruption on the volcano since 25 March, and the largest eruption since the current cycle of activity began at the beginning of March. Pyroclastic flows were observed on the southeast flank of the volcano, descending about 800 m from the its crater.

A five kilometre high ash column above Mount Shinmoedake, Japan, on 5 April 2018. Note the lightning in the upper part of the column; such strikes are common in large ash columns, which can build up considerable charge variations due to friction between particles, leading to frequent electrical discharges. Kyodo News.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Kyūshū 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 volcanoes of the Ryukyu Islands and Kyūshū.

The movement of the Pacific and Philippine Plates beneath eastern Honshu. Laurent Jolivet/Institut des Sciences de la Terre d'Orléans/Sciences de la Terre et de l'Environnement.

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