Report on Aira (Japan) — 8 April-14 April 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 April-14 April 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 8 April-14 April 2009. Smithsonian Institution and US Geological Survey.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
Based on information from JMA, the Tokyo VAAC reported that on 8 April an eruption from Sakura-jima produced a plume that rose to an altitude of 2.7 km (9,000 ft) a.s.l. JMA reported that on 9 April a Vulcanian explosion from Showa crater on the E flank ejected bombs as far away as 1.3 km. A plume rose to an altitude of 4.8 km (15,700 ft) a.s.l. and drifted SW; JMA stated that the plume altitude was the highest altitude a plume reached since June 2006. A pyroclastic flow traveled 1 km E. According to a news article, heavy ashfall was reported in Kagoshima City (about 10 km W), the first ashfall reported there since October 2002. On 10 April, the Tokyo VAAC reported that eruptions produced plumes that rose to altitudes of 2.1-2.7 km (7,000-9,000 ft) a.s.l. and drifted W and S.
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.