A numerical study of conduit flow: Origin of diverse eruption styles by island-arc basaltic magma

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04029
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: National Research Institute for Earth Science and Disaster Prevention (2022); Tohoku University (2019-2021)
• Principal Investigator: Kozono Tomofumi 国立研究開発法人防災科学技術研究所, 火山防災研究部門, 主任研究員 (40506747)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 火道流 / 玄武岩質マグマ / 噴火の多様性 / 数値モデル / 伊豆大島

Outline of Final Research Achievements

We have successfully developed a numerical model of conduit flow for low-viscosity basaltic magma. In particular, applying a thermodynamic equilibrium calculation program for magmas made it possible to incorporate more realistic effects of magma viscosity change due to decompression crystallization and compositional change into the conduit flow model. Based on this model, we systematically investigated the characteristics of the relationship between magma chamber pressure and discharge rate in steady conduit flow, which describes the dynamical system of the conduit flow in a wide parameter range. The results show that the conditions for sub-Plinian and lava flow eruptions in basaltic magma are strongly controlled by conduit geometry and gas escape from magma, respectively.

Free Research Field

火山物理学

Academic Significance and Societal Importance of the Research Achievements

本研究における低粘性の玄武岩質マグマを対象とした火道流数値モデルの開発の成功により、将来の噴火が懸念されている伊豆大島や富士山などで発生し得る、溶岩を流出する非爆発的噴火、噴煙形成・火山灰拡散を伴う爆発的噴火という玄武岩質マグマによる多様な噴火タイプの成因解明が可能となった。噴火タイプの推移予測は、噴火時の周辺地域への影響評価や避難計画などに大きな影響を与えるため、本研究の成果は火山災害の軽減に貢献する重要な社会的意義がある。