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Report on Asamayama (Japan) — 12 April-18 April 2023


Asamayama

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 12 April-18 April 2023
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2023. Report on Asamayama (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 12 April-18 April 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (12 April-18 April 2023)

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


JMA reported that minor inflation on Asamayama's W flank persisted during 10-17 April. The daily number of shallow volcanic earthquakes was 40-80 during 10-14 April and around 40 during 14-17 April. Sulfur dioxide emissions were high at 700 tons per day on 14 April. The Alert Level remained at a 2 (on a scale of 1-5) and warned the public that ejected blocks and pyroclastic flows may travel as far as 2 km from the crater during an eruption.

Geological Summary. 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 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-Asamayama 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 observed activity 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.

Source: Japan Meteorological Agency (JMA)