著者
早川 由紀夫 由井 将雄
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.28, no.1, pp.1-17, 1989-05-31 (Released:2009-08-21)
参考文献数
23
被引用文献数
22 10

The eruptive history of the Kusatsu Shirane volcano is well described by means of 14 beds of key tephra and intercalating loess soil. Three eruptive stages are recognized. During early or middle Pleistocene the Matsuozawa volcano was formed; this is the first stage. The second stage was initiated by effusion of the Horaguchi lava, which was followed by eruptions of the Oshi pyroclastic flow, older lava flows, 3P pumice fall, and Yazawahara pyroclastic flow. Brown loess soil about 10m thick covering these deposits indicates that a dormant period of more than 100, 000 years followed this stage. The summit area upheaved about 400m or more against the foot of the volcano during this period, as is suggested by the extraordinarily steep (6.1°-3.0°) surface of the Oshi ignimbrite plateau. The third stage, which started about 14, 000 years ago, is the formation of three pyroclastic cones on the summit and contemporaneous effusion of the younger lava flows, e. g. the Kagusa lava of 7, 000 years ago and the Sessyo lava of 3, 000 years ago. In historic times, phreatic explosions have frequently occurred on the summit crater, Yugama. This means that the present belongs to the third stage. It is unlikely that eruptions of the third stage are caused by cooling of the magma chamber which was active in the second stage. The activity of the third stage seems to denote arrival of a new magma chamber at shallow depth.

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論文題名に「噴火史」の語を1989年に初めて入れた私がいうのだから一定の説得力があると思う。「草津白根火山の噴火史」 https://t.co/3p7BHH7ayf
早川由紀夫・由井将雄,草津白根火山の噴火史,第四紀研,28,1-17,1989(https://t.co/woDWxGhv8v)を読み、草津白根火山がユニークな履歴を持つ火山と知る。オープンアクセスでどなたでも読めるはずなので、興味ある方はダウンロードを。
草津白根火山の噴火史 早川 由紀夫, 由井 将雄(1989)第四紀研究 https://t.co/3p7BHGPz9F 本白根山は、30万年前の青葉溶岩台地の上に、3000年前にできあがった。高さはわずか150メートル。振子沢溶岩… https://t.co/ZTImFm6inv

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