| Project/Area Number |
14380204
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
WATANABE Koichiro KYUSHU UNIVERSITY, Faculty of Engineering, Professor, 大学院・工学研究院, 教授 (10182916)
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| Co-Investigator(Kenkyū-buntansha) |
IMAI Akira KYUSHU UNIVERSITY, Faculty of Engineering, Associate professor, 大学院・工学研究院, 助教授 (90223304)
NAKANISHI Tetsuya KYUSHU UNIVERSITY, University Museum, Associate professor, 総合研究博物館, 助教授 (50315115)
MOTOMURA Yoshinobu KYUSHU UNIVERSITY, Faculty of Sciences, Research Associate, 大学院・理学研究院, 助手 (20037237)
TAGUCHI Sachihiro Fukuoka University, Faculty of Sciences, Professor, 理学部, 教授 (00108771)
曽 南石 九州大学, 大学院・工学研究院, 助手 (20294887)
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| Project Period (FY) |
2002 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥12,600,000 (Direct Cost: ¥12,600,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2003: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2002: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Keywords | Early Stage of eruption / Magma processes / Mount St.Helens / Juvenile material / Vesicular glass / Micro FTIR / Kuju Volcano / 噴火活動初期 / セントヘレンズ火山 / 発砲ガラス / 火山災害 |
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| Research Abstract |
Early phreatic eruptions may contain juvenile material that provide information about the ascending magma, and thus serve as precursors of impending magmatic eruptions. Samples of early tephra erupted in late March, 1980, from Mount St.Helens, were collected seven weeks before the lateral blast and climactic Plinian eruption that followed on May 18. Recently, sparse, vesicular glass shards that were found in these early tephra samples were reexawmined. Light density fractions from several samples of early tephra were concentrated with some fresh, microlite-poor vesicular glass shards detected in the tephra erupted in March 28 1980. The glass shards were then analyzed using electron microprobe analysis (EPMA) to obtain their chemical compositions for comparison to those of the pre-1980 tephra. Furthermore dehydration process of several shards during heating was measured using micro fourier transform infrared spectrophotometery (Micro-FTIR) to estimate the extent of hydration. Results of these experimentas follows;(1)The 1980 early tephra erupted from Mount St.Helens contained not only the material from the pre-1980 tephra layers (recycled material) but also juvenile material (although the amount was very small). (2)A half of vesicular glass shards in SH0328 are identified juvenile material with the remaining shards from pre 1980 tephra layers (mainly from P tephra). The shards from two different origins can be divided by difference of chemical composition. Juvenile vesicular glass shards could be distinguished from those derived from the pre-1980 tephra layers by difference of chemical composition. (3)Of the vesicular glass shards erupted from Mount. St.Helens, glass shards aged more than several ten thousands can be distinguished from those aged less than several thousands by dehydration curve. Thus, there is a possibility that direct participation of ascending magma could be predicted with this technique using tephra from earlier stages of eruptive activity.
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