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JohnD
2014-Sep-29, 09:01 PM
Large, sudden, without-warning eruption of Mt.Ontake has killed many and injured others who were climbing on the mountain sides.

It's believed not to be a large lave eruption, with the preceding magma shifts that can be measured, but a steam explosion - a phreatic eruption - as water seeped into hot rocks below.

Is this the fate of Barthabunga, as the magma reaches along the fault as far as Askja Lake, the caldera of the the 1875 eruption, one of the biggest of all time?

John

Squink
2014-Sep-29, 11:10 PM
Magma plumbing system beneath Ontake Volcano (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2F Takeyoshi_Yoshida%2Fpublication%2F230377110_Magma_ plumbing_system_beneath_Ontake_Volcano_central_Jap an%2Flinks%2F00b7d52c8ed41c1e79000000&ei=n-QpVNbvCcGkyATX1ID4Ag&usg=AFQjCNF5838oki6e1OYtAMof6eBK5XXcSA&sig2=JdIwiduBkQzkWYlcsCBD8Q) - PDF

Includes a nice map of the plate boundaries around Ontake. Turns out Ontake is on the Eurasia plate, while nearby Fuji lies in the Philippine sea plate. Both overlie subducted Pacific plate. It's not clear that the recent great earthquake (2011) pressurized the Ontake magma chamber(s) to the same extent it did Fuji's.

Squink
2014-Oct-06, 01:12 PM
Japan News: Volcanic eruptions linked to quakes (http://the-japan-news.com/news/article/0001621981)
Masaaki Churei, a former official at the Japan Meteorological Agency who is familiar with the links between earthquakes and volcanoes, said: “When a huge earthquake occurs off the Sanriku coastline, volcanoes that have remained dormant tend to erupt two or three years after the earthquake. It’s possible the Great East Japan Earthquake instigated the eruption of Mt. Ontake.”

JohnD
2014-Oct-06, 08:54 PM
Was he comparing like-with-like?
Ontaksan's was a phreatic, not a magmatic eruption.
JOhn

Squink
2014-Oct-07, 02:41 PM
Was he comparing like-with-like?Hard to tell. This went through a journalist, rather than peer review.

Inclusa
2014-Oct-08, 06:50 PM
Was he comparing like-with-like?
Ontaksan's was a phreatic, not a magmatic eruption.

So, steam explosion in other words?