- VolcanoMashu volcano is a 7 km wide caldera in NE Hokkaido, Japan. The caldera formed ca. 7000 years ago and truncates a stratovolcano which formed the ESE rim of the large Kutcharo caldera to the west. The steep-walled Mashu caldera contains Lake Mashu (摩周湖 Mashū-ko), known for its very clear water, and is one of the scenic highlights of Hokkaido.
Volcano type caldera normal or dormant Location Japan Summit elevation 855 m / 2,805 ft Mashu volcano eruptions 1080 ± 100 years, 350 AD ± 100 years, 150 AD ± 100 years, 2050 BC ± 40 years, 2800 BC ± 1000 years, 3550 BC ± 40 years, 5550 BC ± 100 years (Plinian eruption, caldera formation) (radiocarbon dated) Typical eruption style explosiveA small andesitic stratovolcano, Kamuinupuri, was constructed beginning about 4000 years ago in the SE part of of the deep caldera lake. The latest dated eruption of the volcano was a large explosive eruption about 1000 years ago, which created a 1.2 x 1.5 km crater at the summit of Kamuinupuri.
Kamuishu is a small island in the center of Lake Mashu. It is the tip of a mostly submerged dacitic lava dome.