著者
宮本 毅 中川 光弘 長瀬 敏郎 菅野 均志 大場 司 北村 繁 谷口 宏充
出版者
東北大学東北アジア研究センター
雑誌
東北アジア研究 = Northeast Asian studies (ISSN:13439332)
巻号頁・発行日
no.7, pp.93-110, 2003-03-31

Baitoushan volcano (Changbaishan volcano in China), situated on the border between China and North Korea, is one of the most active volcanoes in mainland Asia. The volcanism is divided into three stages, firstly the shield volcano-forming stage effusing large amount of basaltic lava flow, secondly volcanic cone-building stage consisting of trachytic magma, and finally summit caldera (called Tianchi caldera)-forming stage erupting the vigorous alkali-rhyolitic pyroclastics. Tianchi caldera has been formed by some huge eruptions (10th century, 4000yBP eruption and more) since Pleistocene. In caldera-forming stage, the time sequence of such huge eruption progress from Plinian pyroclastic fall to following large pyroclastic flow (ignimbrite). Based on our geological and petrological studies and Radiocarbon dating about wood and charcoal samples in pyroclastics, we found that 9th century eruption, unknown until now, has occurred before 10th century eruption. From the relation of stratigraphy and radiocarbon age the dormancy between this episode and 10th century one is estimated about a hundred year. The time sequence and eruptive style of this new episode is similar to 10th century eruption, but the magma composition is different.
著者
山本 裕朗 谷口 宏充
出版者
東北大学
雑誌
東北アジア研究 (ISSN:13439332)
巻号頁・発行日
vol.3, pp.201-232, 1999-03-31

Numerous cinder cones from Ojikajima monogenetic volcanic group are well-exposed by marine erosion that allows a detailed investigation of the proximal products. Observation of the exposures at sea cliffs and petrological study of the volcanic rocks revealed the formation process and the internal structure of cinder cones. These cones are divided into three types in terms of evolution: 1) scoria cone+lava flow, 2) spatter cone+lava flow, 3) maar,tuff-ring (phreato-magmatic phases)+scoria cones+lava flow. Four eruption styles of lava flow are found: 1) over flow from crater edge, 2) outflow from middle part of scoria cone with horseshoe-shaped collapse (intrusion of dike oblige from fissure), 3) without collapse, 4) outflow from middle part or basement (intrusion of dike parallel to fissure).論文Article