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Report on Aira (Japan) — 7 January-13 January 2015


Aira

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 7 January-13 January 2015
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2015. Report on Aira (Japan) (Sennert, S, ed.). Weekly Volcanic Activity Report, 7 January-13 January 2015. Smithsonian Institution and US Geological Survey.

Weekly Report (7 January-13 January 2015)

Aira

Japan

31.5772°N, 130.6589°E; summit elev. 1117 m

All times are local (unless otherwise noted)


JMA reported that four explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 5-9 January. Incandescence from the crater was visible at night during 7-8 January. Inflation continued to be detected. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 7-8, 10, and 12-13 January plumes rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted SE, SW, and NW. On 8 and 10 January pilots observed ash plumes that rose to altitudes of 1.5 km (10,000 ft) a.s.l. The Alert Level remained at 3 (on a scale of 1-5).

Geological Summary. 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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Sources: Japan Meteorological Agency (JMA), Tokyo Volcanic Ash Advisory Center (VAAC)