Friday, 8 May 2015

Alert level around Mount Hakone raised amid fears of a phraetic erruption.

Authorities in Kanagawa Prefecture have closed off an area of Mount Hakone, a popular tourist destination, following a rise sharp in seismic activities since 26 April 2015. An area of around 300 m around the Oowakudani Vent, as authorities are concerned about the possibilities of a phraetic eruption (explosion caused by water coming into contact with hot lava and vapourising). The Hakone area is noted for its hot springs, which are caused by water coming into contact with burried hot rocks, then rising to the surface, however Earthquakes near volcanoes are often caused by liquid magma moving through chambers beneath the volcano, and can be symptoms of future eruptions. In the case of Hakone there is a concern that magma closerto the surface my come into contact with liquid water, leading to explosions capable of throwing debris into the air at the surface.

 Steam burst at a hot spring in the Owakudani hot spring district of Mt. Hakone on 6 May 2015. Such bursts are common in the area, but have become larger and more frequent in the past week, wich may be a sign of liquid magma close to the surface. Kyodo News.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Eastern Honshu area lies on the boundary between the Pacific, Eurasian and Philipine Plates, where the Pacific Plate is passing beneath the Eurasian and Philipine Plates as it is subducted into the Earth. This is not a smooth process; the rocks of the two plates constantly stick together, only to break apart again as the pressure builds up, causing Earthquakes in the process. 
 The approximate location of Mount Hakone. Google Maps.
Mount Hakone is located directly on the Bonin Arc, a chain of volcanoes fed by liquified material from the Pacific Plate which is melted by the heat of the Earth's interior and rises through the overlying Eurasian Plate.
 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.
 
See also...

http://sciencythoughts.blogspot.co.uk/2015/02/magnitude-57-earthquake-off-east-coast.htmlMagnitude 5.7 Earthquake off the east coast of Honshū Island, Japan.                                  The Japan Meteorological Agency (which also monitors seismic activity) recorded a Magnitude 5.7 Earthquake at a depth of 50 km off the coast of Iwate Prefecture, slightly after 1.45 pm Japan Standard Time (slightly after 4.45 am GMT) on Tuesday 17 February 2015. There...
http://sciencythoughts.blogspot.co.uk/2014/11/magnitude-68-earthquake-in-nagano.htmlMagnitude 6.8 Earthquake in Nagano Prefecture, Japan.                                                 The Japan Meteorological Agency (which also monitors seismic activity) recorded a Magnitude 6.8 Earthquake at a depth of 10 km in Nagano...
Ten people have been confirmed dead and 63 have been injured following an unpredicted eruption of Mount Ontake on central Honshū on Saturday 27 September 2014. At least 26 people remain...

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