Large-scale Caldera-forming Eruption and Active Post-caldera Volcano: General Geology and Representative Outcrops of Toya Caldera and Usu Volcano, Southwestern Hokkaido, Japan

Abstract

 Toya caldera, eastern Hokkaido, was formed approximately 110 ka, and has two post-caldera volcanoes, Nakajima and Usu volcano. Caldera-forming eruptions ejected a large-scale Toya pyroclastic flow, and related co-ignimbrite ash which covered a wide area in northern Japan. Usu volcano is one of the most active volcanoes in Japan, and has had repeated magmatic eruptions during historical time since AD 1663. The latest major eruption occurred in AD 2000. General geology and representative outcrops of eruptive deposits from Toya caldera and its post-caldera volcanoes are introduced, on the basis of a training field course at the 6^th IAVCEI Collapse Caldera Workshop held in September 2016.