Report on Aira (Japan) — 23 April-29 April 2014
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 23 April-29 April 2014
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2014. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 23 April-29 April 2014. Smithsonian Institution and US Geological Survey.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
JMA reported that seven explosions from Showa Crater at Aira Caldera’s Sakurajima volcano during 22-25 April ejected tephra as far as 1,300 m. Incandescence from the crater was detected at night. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 23-24 and 26 April plumes rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted NW, W, and SE. On 26 April a pilot observed an ash plume that rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted WNW. An explosion was reported on 29 April.
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.