The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 6-13 January. Nightly crater incandescence was visible in webcam images. Explosions at 1451 and 1913 on 6 January, at 1946 and 2225 on 7 January, at 0516 on 8 January, and at 0449 on 12 January produced ash plumes that rose 0.9-1.5 km above the crater rim and drifted SE. All of the explosions, except for those at 1451 on 6 January and at 1946 on 7 January, ejected large blocks 300-1,100 m above the crater rim. An eruptive event at 0541 on 12 January produced an ash plume that rose 1.2 km above the crater rim and drifted SE. 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)