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Report on Aira (Japan) — 4 March-10 March 2009


Aira

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 4 March-10 March 2009
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2009. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 4 March-10 March 2009. Smithsonian Institution and US Geological Survey.

Weekly Report (4 March-10 March 2009)

Aira

Japan

31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)


During 7-10 March, JMA reported that 12 Vulcanian explosions occurred from Showa Crater, on the E flank of Sakura-jima. Some explosions were seen from JMA's Kagoshima Observatory; observers reported that ejected bombs landed as far away as 800 m from the crater and plumes rose to an altitude of 2.9 km (9,500 ft) a.s.l. Based on information from JMA, the Tokyo VAAC reported that an eruption on 7 March, and explosions during 8-10 March, produced plumes that rose to altitudes of 1.8-2.7 km (6,000-9,000 ft) a.s.l. Plumes drifted N and S during 8-10 March. [Correction: Ejected bombs landed as far away as 1,800 m from the crater.]

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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Sources: Japan Meteorological Agency (JMA), Tokyo Volcanic Ash Advisory Center (VAAC)