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タイトル: Some Geological Considerations on the Ha-yama Volcano
その他のタイトル: 葉山火山の地質学的考察
著者: Ichimura, Takeshi
著者(別言語): 市村, 毅
発行日: 1963年7月30日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第41冊第2号, 1963.7.30, pp. 391-402
抄録: (i) The Ha-yama Volcano rises up to 687.4 m. above sea-level at the opposite side of Kaminoyama, resting upon the upper Miocene sediments called the Dorobu formation and plagioryholite which were disturbed and eroded to some degree. (ii) The volcano is formed of lavas and ejecta. One of these is the Sengoku lava, while the other is the Ha-yama lava and agglomerate, both being represented by two-pyroxene andesite rich in brown glass. They were erupted from the crater now broken by the subsequent explosion and opened north-westwards. (iii) The Sengoku lava first poured out and covered largely the undulatory surface of bases rocks composed of the Dorobu formation and plagiorhyolite. It was then followed by the eruption of the Ha-yama lava and agglomerate from the same crater. In this case, the lava flow passes locally into agglomerate at its base. (iv) These lavas are different in the texture of the groundmass and also in the chemical character. In the latter case, the Ha-yama lava seems to be more acidic when compared with the Sengoku lava. (v) The Ha-yama Volcano was born at the area where the Dorobu formation had accumulated under the lacustrine environment. It was active in the Quaternary. The formation of the volcano has, therefore, no direct connection with the deposition of the Dorobu formation which consists of tuffaceous sediments intercalated by lava flows and suggests that there was also a volcanism during its deposition.
URI: http://hdl.handle.net/2261/12117
ISSN: 00408972


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