JMA reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 22-29 July. Nighttime crater incandescence was visible in webcam images. An eruptive event at 0249 on 23 July produced an ash plume that rose 1.1 km above the crater rim and drifted N. Sulfur dioxide emissions were relatively low, averaging 800 tons per day (t/d) on 24 July, and lower than the average of 2,400 t/d on 5 July. Eruptive events at 1155 on 27 July and at 0208, 0514, and 1439 on 28 July produced ash plumes that rose 1-1.8 km above the crater rim and drifted mainly N. An explosion at 1646 on 29 July generated a large ash plume that rose 4.4 km above the crater rim and drifted SE and ejected large blocks 1.3-1.7 km from the crater rim. An ash plume from an eruptive event at 1856 on 29 July rose 1.1 km above the crater rim and drifted S. 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)