Mashu is a caldera. It has not erupted in historic time. Large eruptions occurred in 4875 B.C. and in 970 A.D. The eruption in 4875 B.C. was from the central vent and produced pyroclastic flows. The eruption in 970 A.D. was the most recent at Mashu. It was from a flank vent. Photograph courtesy of and copyrighted by Paul J. Buklarewicz.
Location map for the Kutcharo and Mashu calderas from Newhall and Dzurisin (1988).
Space Shuttle photo STS059-0154-0113 looking southwest across east Hokkaido.
Mashu. Photograph by Mike Lyvers
The following are additional photos of Lake Mashu. Photographs courtesy of and copyrighted by Mike Lyvers.
Space Shuttle photo STS059-0207-0037 of the Shibetsu area.
Source of Information:
Newhall, C.G., and Dzurisin, D., 1988, Historical unrest at large calderas of the world: U.S. Geological Survey Bulletin 1855, 1108 p.
Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.