1999 Fiscal Year Final Research Report Summary
Investigation of volcanic ash monitoring system to predict the manner of magma
| Project/Area Number |
09558050
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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 | 展開研究 |
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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 Univ., Dept. of Earth Resources, Eng., Assoc. Prof., 工学研究科, 助教授 (10182916)
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| Co-Investigator(Kenkyū-buntansha) |
TAGUCHI Sachihiro Fukuoka Univ., Dept. of Earth Science, Professor, 理学部, 教授 (00108771)
WATANABE Kazunori Kumamoto Univ., Dept. of Earth Science, Professor, 教育学部, 教授 (10040049)
IZAWA Eiji Kyushu Univ., Dept. of Earth Resources, Eng., Professor, 工学研究科, 教授 (50037751)
NAKANISHI Tetsuya Kyushu Univ., Dept. of Earth Resources, Eng., Research Assistance, 工学研究科, 助手
MOTOMURA Yoshinobu Kyushu Univ., Dept. of Earth and Planet Sciences, Research Assistance, 理学研究科, 助手 (20037237)
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| Project Period (FY) |
1997 – 1999
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| Keywords | volcanic ash monitoring / Unzen Volcano / juvenile material / vesiculated glass / Kuju Volcano / manner of magma / non-hydrated glass / 顕微FTIR |
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| Research Abstract |
Volcanic ash erupted in an initial stage of volcanic activity has possibility to contain juvenile material directly deprived from latent magma. Detailed studies of the extracted juvenile material may provide effective information to predict magma composition and the manner of magma involving timing and scale of eruption if it will occur. Therefore, monitoring system of volcanic ashes may be one of a potential tool to mitigate volcanic disasters. Based on this concept, we have examined a series of volcanic ash samples erupted from Fugen-dake in Unzen volcano during 1990-1991 and from Iwo-yama in Kuju volcano erupted in 1995, located in the central part of Kyushu island in SW Japan.
In order to asses the existence of latent magma near the surface, we collected ash samples erupted from November 1990 to April 1991 in Unzen. Under a microscope, we found a small amount of vesiculated volcanic glasses with remarkably low refractive index in ash erupted on February and April, 1991. We predicted that the existence of latent magma in the shallow level on the basis of our observation. To confirm that the vesiculated volcanic glass is juvenile material, the vesiculated glass without impurities were extracted as glass flakes from each polished this sections. These glass flakes were sprited into two aliquots. One is for measurement of untreated refractive index and other is for measurement of refractive index after annealing to dehydrate. The vesiculated volcanic glass in ash indicated almost the same value in these two kinds of refractive index. Thus the non-hydrated vesiculated volcanic glass in ash seems to be from new magma. It means that these glasses are newly produced because these have not experienced hydration after the formation. The detection of essential material at the time processed more than three months of the lava dome appearance suggests that the monitoring of the volcanic ash is effective for prediction of the manner of latent magma and magmatic eruption.
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Research Products
(10 results)
