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Thread: Let's talk Ontakesan

  1. #1
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    Let's talk Ontakesan

    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

  2. #2
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    Magma plumbing system beneath Ontake Volcano - 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.

  3. #3
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    Japan News: Volcanic eruptions linked to quakes
    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.”

  4. #4
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    Was he comparing like-with-like?
    Ontaksan's was a phreatic, not a magmatic eruption.
    JOhn

  5. #5
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    Quote Originally Posted by JohnD View Post
    Was he comparing like-with-like?
    Hard to tell. This went through a journalist, rather than peer review.

  6. #6
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    Quote Originally Posted by JohnD
    Was he comparing like-with-like?
    Ontaksan's was a phreatic, not a magmatic eruption.
    So, steam explosion in other words?

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