The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 20-27 January. Nightly crater incandescence was visible in webcam images. On 20 January sulfur dioxide emissions were extremely high, averaging 3,200 tons per day. Explosions at 1220 on 21 January, 1709 and 2246 on 22 January, 0243 on 23 January, and 1626 on 25 January produced ash plumes that rose 800-2,500 m above the crater rim and drifted E, SE, S, and SW. Some explosions ejected large blocks 900-1,300 m from the crater rim. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 km away from both craters.

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.

Source: Japan Meteorological Agency (JMA)