地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
論説
八甲田カルデラ東方,八幡岳火山群の地質と火山活動史
工藤 崇檀原 徹岩野 英樹山下 透
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2020 年 129 巻 1 号 p. 21-47

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 The stratigraphy and spatio-temporal distribution of the Early Pleistocene volcanic rocks in the east of Hakkoda Caldera, Northeast Japan were revealed. The Hachimandake Volcanic Group (HVG) was newly distinguished in this area. Volcanic activity of the HVG occurred during 2.5-1.4 Ma. Basaltic andesite magma erupted from several eruptive centers and formed several small volcanic bodies in the east of the present Hakkoda Caldera. Volcanic activity of the HVG is characterized by repeated outflows of basaltic andesite lava flows, each several meters thick. Volcanic activity of the HVG was notably smaller than that of Minami- and Kita-Hakkoda Volcanic Groups from 1.1 Ma to the present. Dacite to rhyolite pyroclastic flows were found to have occurred simultaneously during HVG activity. Those source vents are unknown.

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© 2020 公益社団法人 東京地学協会
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