Report on Aira (Japan) — 6 November-12 November 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 November-12 November 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 November-12 November 2019. 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 incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible at night during 5-11 November. There were 13 explosions and 25 non-explosive eruptive events detected by the seismic network. Blocks were ejected as far as 1.3 km away. Explosions at 1557 and 1615 on 7 November generated ash plumes that rose 3.8 and 3.5 km above the crater rim, respectively. An explosion at 1724 on 8 November generated an ash plume that rose 5.5 km above the crater rim and drifted E, and ejected large blocks that fell 500-800 m away. The last time plumes rose over 5 km from the active vents was on 26 July 2016 at Showa Crater and on 7 October 2000 at Minamidake Crater. The Alert Level remained at 3 (on a 5-level scale).
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.