Global Volcanism Program | Image GVP-10540
The deep blue waters of 6-km-wide Mashu caldera are seen here from its western rim. The small island of Kamuishu in the center of Lake Mashu (right-center) is the tip of a mostly submerged lava dome. Mashu is a Holocene caldera of a volcano constructed on the ESE rim of the Kussharo caldera. Following caldera collapse, Kamuinupuri (whose lower flanks are visible at the far right) formed beginning about 4,000 years ago.
Copyrighted photo by Shun Nakano, 2001 (Japanese Quaternary Volcanoes database, RIODB, http://riodb02.ibase.aist.go.jp/strata/VOL_JP/EN/index.htm and Geol Surv Japan, AIST, http://www.gsj.jp/).