Report on Aira (Japan) — 14 August-20 August 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 August-20 August 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 August-20 August 2013. 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 24 explosions at Sakura-jima's Showa Crater were detected during 12-19 August and ejected tephra as far as 1.8 km. Incandescence from the crater was observed on 14 August. A very small eruption from Minami-dake Crater occurred on 16 August, producing an ash plume that rose 200 m.
An explosion from Showa Crater on 18 August generated a large ash plume that rose 5 km above the crater and drifted NW. A small pyroclastic flow traveled SE. According to news sources, the 50-minute-long eruption produced ashfall in the central and northern parts of Kagoshima (10 km W), causing train delays and poor visibility for car drivers. The event was the 500th explosion this year.
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.