Report on Hokkaido-Komagatake (Japan) — March 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 3 (March 1996)
Managing Editor: Richard Wunderman.
Hokkaido-Komagatake (Japan) Additional information about the 5 March eruption
Please cite this report as:
Global Volcanism Program, 1996. Report on Hokkaido-Komagatake (Japan). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 21:3. Smithsonian Institution. https://dx.doi.org/10.5479/si.GVP.BGVN199603-285020.
42.063°N, 140.677°E; summit elev. 1131 m
All times are local (unless otherwise noted)
Volcanic tremor was registered for six minutes starting at 1810 on 5 March by the JMA station 4.1 km WSW of the crater. During this activity, two main vents opened on and near the S side of Showa 4-nen (1929) crater. A line of vents extending ~200 m N-S formed on the S part of the crater floor. Strong eruptive activity was observed until 7 March and then decreased. Volcanic earthquakes had increased somewhat prior to the eruption, but seismicity remained low afterwards through mid-April.
Geologic Background. The truncated Hokkaido-Komagatake volcano on the Oshima Peninsula of southern Hokkaido is one of the most active volcanoes of Japan's northernmost island. The 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 CE. Hummocky debris avalanche material occurs at the base of the volcano on three sides. Much of the andesitic 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.
Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.