The history of caldera-forming eruptions in eastern Hokkaido, Japan

Abstract

The eruptive history and magma systems of large-scale eruptions (VEI>5) in eastern Hokkaido, Japan was reviewed on the basis of resent studies. Approximately 80 tephra layers were derived from Akan, Kutcharo, Atosanupuri and Mashu volcanoes in the past 1.7 Ma. The latter two are the post caldera, active volcanoes of Kutcharo. Total volume of all tephras is 1000 km3. Their discharge rate is remarkably increased at 0.4~0.2 Ma from 0.2 to 2.0 km3/ky. This rate is not decreased during the last 3.5 ky, post caldera stage of Kutcharo. Although silicic magma systems of Akan, Kutcharo and Mashu were distinct, chemistry of Atosanupuri magma is similar to Kutcharo's one.