著者

菅 香世子 小林 勝己 印牧 もとこ 宮原 智哉 遠藤 邦彦

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.37, no.2, pp.71-83, 1992

参考文献数

21

被引用文献数

4

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Kozushima consists of rhyolitic monogenetic volcanoes (lava domes and thick lava flows), and is located on Zenisu Ridge, northern part of Izu-Bonin Arc. Activities of the momogenetic volcanoes were accompanied with pyroclastic flows and surges. But their succession and stratigraphy are not well known. We tried to discuss them based on observation in construction field of Kozushima Airport and its neighborhood in southern part of the island. Three pyroclastic surge deposits were confirmed on thick lava flow which was fomed tens of thousands years ago. They are, Chichibuyama pyroclastic-surge deposit-B which was older than 22,000 y.B.P., Chichibuyama pyroclaslic-surge deposit-A which erupted 21,000-19,000y.B.P. and Tenjosan pyroclastic-surge deposit which was fomed 838 A.D. in ascending order. Two regional ash-fall deposits which originated from gigantic eruptions in Southern Kyushu and several ash-fall deposits from another islands were interbeded with them. Thus, only three pyroclastic surge deposits have come to deposit in southern part of Kozushima while tens of thousands years. It does not mean that only three eruptions occurred in Kozushima the while, but suggests that most eruptions could not bring pyroclasic materials on the thick lava flow whose height is 100-300 m in southern part of Kozushima except above mentioned three eruptions. Most pyroclastic flows and surges were strongly controled by topography in Kozushima, but some were not. That might be caused by the difference of eruption energy or eruption types.

著者

菅 香世子

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.37, no.2, pp.59-75, 1998-05-31 (Released:2009-08-21)

参考文献数

48

被引用文献数

3 4

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伊豆・小笠原弧北部の火山フロントに位置する八丈島火山群は,活動年代が異なる複数の小型成層火山の複合体である.入丈島火山群を構成する各火山の原形と生成順序は,それらの地質と火山地形から推定することができる.八丈島火山群の火山は,安山岩を主体とする火山と,玄武岩を主体とする火山とに分けられ,後者でも活動の後期には安山岩あるいはデイサイトマグマが活動することがある.このため,八丈島火山群では安山岩の産出頻度が高い.また,最近の10数万年間だけでも7~8個の小型成層火山が生成されてきた八丈島火山群は,マグマの上昇径路となる開口割れ目が比較的生じやすい条件下にあるといえる.八丈島火山群は,伊豆・小笠原弧北端部と本州弧との衝突に起因するNW-SE方向の圧縮の影響を多少は受けているものの,基本的には伊豆・小笠原弧で卓越する伸張のテクトニクストの下に置かれていると考えられる.

著者

平田 大二 山下 浩之 谷口 英嗣 菅 香世子 西川 正 青池 寛 有馬 眞 鈴井 正和

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1996, no.2, 1996-11-05