小値賀島単成火山群の火山地質

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Other Title
  • Geology of the Ojikajima Monogenetic Volcano Group

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Description

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).

Journal

  • Northeast Asian studies

    Northeast Asian studies (3), 201-232, 1999-03-31

    東北大学東北アジア研究センター

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