Report on Asamayama (Japan) — October 2012
Bulletin of the Global Volcanism Network, vol. 37, no. 10 (October 2012)
Managing Editor: Richard Wunderman.
Asamayama (Japan) No changes in high-temperature areas around summit crater; seismicity remained low
Please cite this report as:
Global Volcanism Program, 2012. Report on Asamayama (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 37:10. Smithsonian Institution.
36.406°N, 138.523°E; summit elev. 2568 m
All times are local (unless otherwise noted)
Asama's quiescence during May-December 2009 noted in our previous report (BGVN 35:10) continued into 2010. Only two minor incidents were noteable during the end of the year. During 11-12 November seismic activity was at a low level, though it was slightly above background. White plumes were seen rising to a height of ~100-400 m above the crater. No remarkable changes were noted by either GPS or tiltmeter observations. Alert Level 1 continued during this period.
An observation flight was conducted in cooperation with the Japan Ground Self-Defense Force (JGSDF) on 2 November. High-temperature areas were confirmed in and around the center of the summit crater. No changes in the distribution of thermal anomalies was detected since the last observation on 13 April. The SO2 flux averaged ~200-300 tonnes/day (t/d) during November.
In December, seismic activity continued at a low level except for a slight increase during 28-31 December. A white plume was observed rising ~100-300 m above the crater. The SO2 flux measured an average of 100-300 t/d. No remarkable changes were noted by either GPS or tiltmeter observations.
There was no exceptional activity during either 2011 or 2012 to date.
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: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ke Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).