Report on Asamayama (Japan) — November 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 11 (November 1980)
Managing Editor: David Squires.
Asamayama (Japan) Frequent seismicity continues
Please cite this report as:
Global Volcanism Program, 1980. Report on Asamayama (Japan) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 5:11. Smithsonian Institution.
36.406°N, 138.523°E; summit elev. 2568 m
All times are local (unless otherwise noted)
Monthly seismicity at Asama increased from 1,114 recorded events in September to [1,365] in October, the highest monthly total since August 1977. Seismic activity decreased to 897 recorded events in November. No eruption or increase in steam emission were observed. Asama last erupted in 1973, when the earthquakes reached 5,612 per month.
Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.
Information Contacts: JMA, Tokyo.