栗駒火山の形成史

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Kurikoma volcano is located at the volcanic front of northeastern Japan arc. The volcano can be divided into 6 volcanic edifices on the bases of the inferred eruption centers, relative preservation of primary micro-topographic features on the eruptive materials, and stratigraphic relations. Lava flow has been dominant through the development history of each edifice, while pyroclastic deposits are conspicuous near the craters of several ones. Newly analyzed 7 K-Ar ages for the representative samples range from ca. 0.53 to around 0.11 Ma, practically reconcilable with the stratigraphy. Based on these data, an internally consistent scenario on the development history is summarized as follows: 1) Magmatic eruption started at about 0.5 Ma to make up the southern volcanic row. South and east to northeast flank of the Higashi-Kurikoma volcanic edifice was probably formed nearly the same time. Following these eruptions from the southern vents, central vents effused lava flows, resulting to build the Higashi-Kurikoma edifice and Kokuzou lavas (part of Kurikoma edifice) around 0.4 Ma. 2) After terminating eruption from the southern and east-north eastern vents, the Higashi-Kurikoma vent had been active until 0.1 Ma, and Kurikoma vent lasted several tens of thousands years ago. 3) Magusadake cone was built through repeated lava effusions from several vents in the western part of the volcano from 0.45 Ma to 0.1 Ma. 4) Viscous magma erupted to form Tsurugidake lava dome as the last event of magmatic eruption so far in the Sukawa horse-shoe shaped crater which was formed in northern portion of the Kurikoma (Okomayama) volcanic edifice.
特定非営利活動法人日本火山学会の論文
2001-11-20

栗駒火山の形成史

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