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Report on Suwanosejima (Japan) — August 1979


Suwanosejima

Scientific Event Alert Network Bulletin, vol. 4, no. 8 (August 1979)
Managing Editor: David Squires.

Suwanosejima (Japan) Activity since January 1977 tabulated

Please cite this report as:

Global Volcanism Program, 1979. Report on Suwanosejima (Japan) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 4:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197908-282030



Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Activity has been observed only once since mid-March (table 1), in contrast to the pattern of the preceding 26 months. From January 1977-March 1979 there were 1-4 periods of tephra ejection per month, each lasting up to a few days.

Geological Summary. The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two active summit craters. The summit is truncated by a large breached crater extending to the sea on the E flank that was formed by edifice collapse. One of Japan's most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits covered residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating an open collapse scarp extending to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: JMA, Tokyo.