Komaga-take

Japan - Hokkaido

SUMMARY:

Type: composite
Activity: active
Last Eruption: 1996 AD
Rock Type: ?
Eruptive Volume: ? cu km
Location Map from Xerox PARC
Latitude: 42.07 N
Longitude: 140.68 E

Geologic Background:

The truncated Komaga-take volcano sits 30 km north of Hakodate City on the Oshima Peninsula of southern Hokkaido. It is one of the most active volcanoes of Japan's northernmost island. The andesitic stratovolcano has a 2-km-wide horseshoe-shaped caldera open to the east, that formed as a result of edifice collapse. Hummocky debris avalanche material occurs at its base on three sides. Much of Komaga-take 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 volcano has generated large pyroclastic eruptions, including historical eruptions in 1640, 1856, and 1929.

Historic 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.
  • On June 17, 1929, a large eruption included pumice fall and pumice flows killed 2 people and damaged 2000 homes. The volcano last erupted in November 1942.

Recent Activity:

  • Seismicity has generally remained low since 1966 except for earthquake swarms in June 1983 and December 1989.
  • Volcanic tremor was registered for 6 minutes prior to eruption which began on March 5, 1996. During this activity two main vents opened on and near the south side of Showa 4-nen (1929) crater. Strong eruptive activity was observed until March 7. Steaming has continued thru May.
  • A small-scale phreatic eruption on Oct. 25, 1998.
  • Two small eruptions on Sept. 4 & Sept. 28, 2000.

Data Sources

  • Global Volcanism Network (V. 15, No. 5 to V. 25, No. 8).

ADDITIONAL INFORMATION

Last Update: 12/10/00