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Report on Izu-Oshima (Japan) — December 1990

Bulletin of the Global Volcanism Network, vol. 15, no. 12 (December 1990)
Managing Editor: Lindsay McClelland.

Izu-Oshima (Japan) Decreased seismicity; continued steam emissions

Please cite this report as:

Global Volcanism Program, 1990. Report on Izu-Oshima (Japan). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 15:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199012-284010.

Volcano Profile |  Complete Bulletin


Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Steady steam emission continued following the 4 October ash emission, reaching 1,000 m above the crater (figure 23). No additional eruptions from Mihara-yama cone had occurred as of 14 January 1991. A total of 57 earthquakes were recorded in December, down from 155 in November. No tremor episodes have been recorded since late April.

Figure (see Caption) Figure 23. Monthly mean estimated plume heights from Oshima, 1987-90. Arrows mark eruptions. Courtesy of JMA.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: JMA.