Report on Aira (Japan) — October 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 10 (October 1992)
Managing Editor: Lindsay McClelland.
Aira (Japan) Increased explosive activity feeds ash plumes and incandescent columns
Please cite this report as:
Global Volcanism Program, 1992. Report on Aira (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:10. Smithsonian Institution.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Eighteen explosions and 18 ash eruptions occurred . . . in October, a significant increase from September. Ten of the 18 seismically recorded explosions produced an incandescent column. The highest column rose 800 m for 60 seconds at 0440 on 20 October, scattering incandescent blocks to 700 m distance. This was the first large incandescent column since glowing material rose 1,000 m on 13 July 1991. The month's highest ash plume rose more than 4 km . . . at 0843 on 22 October. Seismicity was relatively low with no swarms recorded.
Activity continued at a similar rate, with nine explosions and four quiet ash eruptions, through mid-November. The highest ash plume rose 3 km on 11 November. Explosions on 8 and 13 November produced incandescent columns, each lasting 10 seconds and rising 200-300 m.
Geological Summary. 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.