Report on Aira (Japan) — February 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 2 (February 1992)
Managing Editor: Lindsay McClelland.
Aira (Japan) Fewer explosions, but tephra cracks car windshields; seismicity remains high
Please cite this report as:
Global Volcanism Program, 1992. Report on Aira (Japan). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 17:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199202-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
The monthly number of recorded explosions declined from a 6-year high of 60 in January, to 16 in February. Seven car wind shields were cracked by lapilli from an explosion at 1009 on 1 February, and two more were cracked at 0630 on 2 February, when the month's highest plume rose 3.5 km. Seismicity was higher than normal, with swarms of volcanic earthquakes recorded on 4, 7-15, 17-19, and 23-29 February.
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.