The eruption history and silicic magma systems of caldera-forming eruptions in eastern Hokkaido; Japan

摘要

The eruptive history and magma systems of large-scale explosive eruptions (VEI >5) in eastern Hokkaido; Japan; are reviewed on the basis of recently reported high-resolution tephrostratigraphy. More than 70 large-scale explosive eruptions have been recorded from the Akan; Kutcharo; Atosanupuri; and Mashu caldera volcanoes in the past 1.7 Ma. The total tephra volume of these eruptions is estimated to be approximately 1000 km3. The discharge rate increases remarkably from 0.2 km3/kyr to 2.0 km_3/kyr at approximately 0.2 Ma. The discharge rate is still high owing to the recent frequent activity of the Mashu caldera. The silicic magma systems of the Akan; Kutcharo; and Mashu calderas formed independently. On the other hand; the magma of Atosanupuri is associated with that of Kutcharo caldera.