Report on Aira (Japan) — September 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 9 (September 1994)
Managing Editor: Edward Venzke.
Aira (Japan) Eruptive activity decreases
Please cite this report as:
Global Volcanism Program, 1994. Report on Aira (Japan) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 19:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199409-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Explosive volcanism continued through September but caused no damage. Nine eruptions occurred . . ., including four explosive ones, a significant decrease from last month. The highest ash plume of September rose to 3,200 m on the morning of 12 September. No volcanic earthquake swarms were detected, but 438 distinct events were registered at a seismic station 2.3 km NW of Minami-dake crater. Ashfall was sometimes observed at [KLMO], where 425 g/m2 was measured in September.
Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Information Contacts: JMA.