"The truncated Komaga-take volcano on the Oshima Peninsula of southern Hokkaido is one of the most active volcanoes of Japan's northernmost island. Komaga-take's sharp-topped 1131-m-high summit lies at the western side of a large breached crater that formed as a result of edifice collapse in 1640 AD. Hummocky debris avalanche material occurs at the base of the volcano on three sides. Much of the andesitic Komaga-take volcano is Pleistocene in age. Two late-Pleistocene and two Holocene plinian eruptions occurred prior to the first historical eruption in 1640, which began a period of more frequent explosive activity. The 1640 eruption, one of the largest in Japan during historical time, deposited ash as far away as central Honshu and produced a debris avalanche that reached the sea. The resulting tsunami caused 700 fatalities. Three plinian eruptions have occurred since 1640; in 1694, 1856, and 1929."  -Smithsonian Volcano Archive
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