The Japan Meteorological Agency has reported an eruption on Mount Shinmoedake, a 1421 m volcano that forms part of the Kirishima Volcanic Complex on southern Kyūshū Island. The agency began to monitor small Earthquakes beneath the mountain at about 8.15 am Japan Standard Time on Thursday 1 March 2018 (seismic activity beneath volcanoes can be significant, as they are often
caused by the arrival of fresh magma, which may indicate that a volcano
is about to undergo an eruptive episode), which was followed by an eruption at about 11.00 am, which produced an ash column about 300 m high that caused ash-falls in the town of Takaharu, to the east of the volcano. This was followed by several more small eruptions on Thursday 1 and Friday 2 March.
An ash column over Mount Shinmoedake on Kyūshū Island on Thursday 1 March 2018. 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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