Investigation into precursory magma migration into a shallow conduit

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22357
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: Tohoku University
• Principal Investigator: Araya Naoki 東北大学, 理学研究科, 助教 (80880103)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 火山噴火 / マグマ / 噴火メカニズム

Outline of Final Research Achievements

Recently, a noble process “pre-charge”, in which magma migrates into a shallow conduit prior to a large explosive eruption, has been found. This process attract attention because it could control the onset of a large explosive eruption. This study clarified the time sequence of magmatic processes leading to historical explosive eruptions at Sakurajima volcano where the pre-charge was discovered. We found that there was no mafic magma recharge and subsequent mixing, which is often considered as an eruption trigger, just prior to the eruptions. Therefore, the pre-charge could be involved in the final trigger process. It is suggested that the pre-charge could have occurred in some other arc volcanoes. Therefore, this process may be a universal process prior to large explosive eruptions.

Free Research Field

火山学

Academic Significance and Societal Importance of the Research Achievements

本研究では、近年新たに発見され、大規模噴火の発生を支配する過程として注目を集めているプレチャージ現象（噴火に先立つ火道浅部へのマグマ上昇）のタイミングを明らかにすることで、プレチャージ現象が最終的なトリガープロセスに関与している可能性を見出した。これは、噴火の発生予測においてプレチャージ現象の検知が重要であることを意味する。さらに、国内外の噴火事例においてもプレチャージ現象が起きていた可能性があり、普遍的な現象であることが示唆される。普遍性のある新たな現象の発見により、火山噴火メカニズムに関する研究の進展が見込まれるため、その学術的な意義は大きい。