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Report on Aira (Japan) — June 2006


Bulletin of the Global Volcanism Network, vol. 31, no. 6 (June 2006)
Managing Editor: Richard Wunderman.

Aira (Japan) First eruption outside of the summit crater in 58 years

Please cite this report as:

Global Volcanism Program, 2006. Report on Aira (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 31:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200606-282080



31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)

According to Yukio Hayakawa, on 4 June 2006 Sakura-jima erupted. The vent, which was outside the summit crater, was near or within the crater which issued the 1946 (Showa) lava flow, on the E slope of Minami-dake summit. The eruption continued intermittently until the next morning. A small amount of ash fell in Kagoshima city. In the following days it became calm.

Aviation reports noted that ash clouds that reached unknown heights. No ash was visible on satellite imagery.

On 10 June, the Sakura-jima Volcano Research Center reported an increase in low-frequency earthquakes since mid-March and in small tremors with a less than 2 minute duration since mid-May 2006. A thermal anomaly at the volcano grew in size after February 2006.

This was the first reported Sakura-jima eruption from a vent outside the summit crater in 58 years. The 1946 vent was the source of major lava flows that reached the E and S coasts of the former island.

Our last Sakura-jima report noted the frequent ash plumes and eruptions through May 2004 (BGVN 29:05). The Tokyo Volcanic Ash Advisory Center's reports enabled an overview of ash plumes during mid-2005 to mid-2006 (table 13).

Table 13. Sakura-jima plumes during 2 June 2005-19 June 2006. Courtesy of the Tokyo VAAC.

Date Event Plume Type, Height, and Drift
02 Jun 2005 explosion Ash; unknown height
08 Jul 2005 explosion --
10 Jul 2005 explosion --
13-19 Jul 2005 explosion ~1.8 km height; drifting N
21 Jul 2005 explosion --
22 Jul 2005 explosion --
02 Sep 2005 eruption Ash; ~2.1 km high; drifting NW
09 Dec 2005 explosion ~2.7 km height; drifting S
05 Feb 2006 explosion ~1.8 km height; drifting N
19 Apr 2006 explosion ~2.4 km height; drifting NE
28 Apr 2006 explosion Ash; 2.1 km height
01 May 2006 explosion --
04-05 Jun 2006 intermittent Ash clouds; 200-300 m height, unknown drift eruptions
07-12 Jun 2006 -- Ash; unknown height, drift
14, 16, 19 Jun 2006 -- Ash; 2.1 km height

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 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.

Information Contacts: Hayakawa Yukio, Gunma University, 4-2 Aramaki-machi, Maebashi City, Gunma, 371-8510, Japan; Tokyo Volcanic Ash Advisory Center (VAAC), Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: https://ds.data.jma.go.jp/svd/vaac/data/); Sakura-jima Volcano Research Center, Disaster Prevention Research Institute (DPRI), Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan (URL: http://www.dpri.kyoto-u.ac.jp/).