Pre-eruptive magma processes in a magma chamber that led to a catastrophic caldera-forming eruption

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K05616
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Tomiya Akihiko 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 主任研究員 (30357553)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: マグマ・火成岩 / 噴火 / 火山 / マグマ溜まり / 洞爺カルデラ / 斑晶 / 流紋岩 / 軽石

Outline of Final Research Achievements

I conducted a series of petrological and petrographical studies on Toya caldera, Hokkaido, Japan, to investigate the pre-eruptive magma processes in the magma chamber that led to a catastrophic caldera-forming eruption. This study revealed that, just prior to the eruption, a large amount of homogeneous rhyolitic magma was stored at ca. 7 km in depth in the main magma chamber, which had stably existed for a long time. High-temperature magma had been repeatedly injected and mixed into the magma chamber since at least hundreds of years before the eruption, and the last magma mixing occurred just prior to or during the eruption.

Free Research Field

火山学

Academic Significance and Societal Importance of the Research Achievements

洞爺カルデラのマグマ溜まりの深さ・温度，噴火準備過程，およびそのタイムスケール等を明らかにすることができ，カルデラ噴火のメカニズムへの理解の進展に貢献した．また，本研究結果をもとに，地球物理学的モデル化を進めていけば，将来巨大カルデラ噴火の前にどのようなことが観測され得るのかについての指針を与えることが可能と考えられ，防災上の意義も大きい．