Geological findings in the 2021 Nishinoshima comprehensive scientific research project

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  • 2021年に実施された西之島総合学術調査における火山地質学的知見

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Abstract

Through the Nishinoshima comprehensive scientific research project in 2021, we examined the outline of distribution and lithological profiles of the pyroclastic deposits of Nishinoshima volcano after eruption in 2019–2020 (Episode 4), and conducted a preliminary petrological analysis. The 2019–2020 eruption activity changed from andesitic lava outflow to basaltic–andesitic violent strombolian eruption within the period. In the survey conducted, it became clearer that the changes in chemical composition and eruption style occurred around the same time. After a continuation of the violent strombolian eruption, the eruption style changed furthermore to ash eruption or phreatomagmatic eruption, which is characterized by the brittle fragmentation of pyroclastic materials. The eruption style on August 14, 2021 (the first eruption of Episode 5) was inferred to be similar to the late stage of Episode 4, because of their similar ash deposit characteristics.

Journal

  • Ogasawara research

    Ogasawara research 49 45-69, 2023-03

    東京都立大学小笠原研究委員会

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