| Project/Area Number |
13680104
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
自然地理学
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| Research Institution | Nagasaki University |
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Principal Investigator |
NAGAOKA Shinji Nagasaki University, Faculty of Education, Associate professor, 教育学部, 助教授 (80244028)
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| Project Period (FY) |
2001 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Volcanic activity / Explosive erption / Tephra / Pyroclastic flow / Tephra falls (pyroclastic falls) / Kyushu / Volcano / Landform / 噴火 / 溶岩 / 噴火史 / 阿蘇火山 / 九重火山 / 中央火口丘 / 鬼岳火山 / スコリア丘 |
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| Research Abstract |
The four volcanoes in Kyushu were surveyed using tephrochronological and geomorphologyical methods in addition to the ordinary geological one and dating in order to reconstruct high-resolution explosive eruptive histories.
The eruptive history during 100 ka-30 ka of Aira caldera, southern Kyushu, is revealed by tephrostratigraphical studies. In this period, seven explosive eruptions of the caldera are identified. The last 0.1 Ma(=100 ka) is the active period occurring many explosive and effusive eruptions. The Aira pyroclastic eruption at 27 ka(more than 411 km^3 in bulk volume) separates this active period. Total mass of erupted magma during 100 ka-30 ka is 63.3×10^<12>kg. And the average rate is 0.9×10^<12>kg/ky. The Aira caldera had repeated its magmatic eruptions at intervals of ca.7500 years. The Onidake volcano group on Fukue island is one of the monogenetic volcano groups with basaltic lava flows and scoria cones, and contains eleven monogenetic volcanoes. The K-Ar and ^<14>C dating results show that these volcanoes were active during 0.5-0.018 Ma. The average interval of monogenetic volcano-forming eruption is fifty thousand to thirty thousand years. Takenotuji volcano located in the southern part of the island is one of the youngest volcanoes in the Iki island which has late Miocene to Pleistocene volcanoes including scoria cones, shield volcanoes and lava plateau of alkalic and subalkalic rocks. We recognize and describe a total of 14 units formed successively. The K-Ar dating indicates that the volcano occurred in 0.9-0.6Ma. The central strato-volcanoes of Aso volcano have been active during the last 800 ka after the last caldera-forming Aso-4 eruption. The activity has been so continuous without 300-250ka and formed more than 100 tephra units including pumice falls, scoria falls, lithic falls, ash falls, and pyroclastic surges which show various eruption styles occurred in volcanic centers.
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