Saturday, 9 November 2019

Spectacular eruption on Mount Sakurajima, Japan.

The Sakurajima volcano on Kyūshū Island, Japan, underwent a major eruption slightly before 5.25 pm local time on Friday 8 November 2019, producing an ash column more than 5.5 km in height. This is the largest eruption on the volcano since July 2016, and more than the hundredth eruption this year (though with very active volcanoes it can be difficult to give an exact number of eruptions, as they tend to run into one-another). This high level of activity is impressive, but prevents Sakurajima from becoming a major hazard, partly because people tend not to build homes or other structures too close to very active volcanoes, but also because the high levels of activity tend to prevent pressure within the volcano from building up to dangerous levels, which can lead to sudden very large and destructive eruptions on less obviously active volcanoes.

 Eruption on Mount Sakurajima on Friday 8 November 2019. Sengun-en/Reddit.

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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