Report on Aira (Japan) — 29 June-5 July 2011
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 29 June-5 July 2011
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2011. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 29 June-5 July 2011. Smithsonian Institution and US Geological Survey.
31.5772°N, 130.6589°E; summit elev. 1117 m
All times are local (unless otherwise noted)
According to pilot observations, the Tokyo VAAC reported that ash plumes rose from Sakura-jima to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l on 28 and 30 July. Reports from JMA stated that plumes rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. during 30 June-1 July. An explosion was noted on 4 July.
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.