JMA reported ongoing eruptive activity at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) consisting of a few eruptive events and two explosions. Crater incandescence was visible nightly, sometimes characterized as incandescent flashes. An explosion at 0340 on 2 December produced an ash plume that rose as high as 3.2 km above the crater rim and ejected large blocks as far as 1.1 km from the vent. The second explosion, recorded at 1929 on 3 December, produced an ash plume that rose as high as 3 km and ejected large blocks 1-1.3 km away. Webcam video of the event showed incandescent material ejected above the crater and lightning in the ash plume. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

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.

Sources: Japan Meteorological Agency (JMA), Treasure Official Channel