Report on Aira (Japan) — 10 May-16 May 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 May-16 May 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, 10 May-16 May 2017. Smithsonian Institution and US Geological Survey.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
According to JMA, fieldwork at Aira Caldera’s Sakurajima volcano revealed that the sulfur dioxide flux rose from 300 tons on 28 April to 1,700 tons on 8 May; the last time sulfur dioxide flux was above 1,000 tons was 23 June 2015. At 1312 on 12 May an explosion at Showa Crater generated a plume that rose 700 m above the crater rim, into a weather cloud. Four events were detected during 13-15 May; one of the events, an explosion at Showa Crater on 14 May, produced a plume that rose 2.3 km above the crater rim. 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.