Report on Aira (Japan) — 15 November-21 November 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 November-21 November 2017
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2017. Report on Aira (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 November-21 November 2017. 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 an explosion at Minamidake summit crater (at Aira Caldera’s Sakurajima volcano) detected at 2207 on 13 November, ejected material as far as 1.3 km. The explosion vibrated structures in Kagoshima and Miyazaki prefectures. Poor weather conditions prevented views of a plume. An explosion at Showa Crater at 0955 on 14 November produced a plume that rose 1.3 km above the crater rim. Another explosion at Minamidake occurred at 2343 on 14 November, generating a plume that rose 1.3 km above the crater rim. Sulfur dioxide flux measured that same day was 1,400 tons per day, up from 400 tons per day on 10 November. Very small events at Minamidake were occasionally detected during 17-20 November. 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.