JMA reported nightly incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 14-21 December and that the sulfur dioxide emission rate remained high. Four explosions were recorded during 16-18 December. One of the explosions, at 1959 on 17 December, generated a plume that rose 3 km above the crater rim and ejected bombs 1.3-1.7 km away from the crater. Another explosion, at 0439 on 18 December, produced a plume that rose 1.8 km and ejected bombs 1-1.3 km away from the crater. The Alert Level remained at 3 (on a 5-level scale).

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)