July was the first eruption-free month since June 1989, although a white (occasionally gray) plume weakly rose 100-200 m above the crater rim throughout the month. Seismicity in July was about 10% of normal, with 331 small earthquakes recorded. . . . Eruptive activity had not resumed as of 13 September, bringing the sequence of explosion-free days to 159 since 8 April. This is the longest explosion-free period in over 20 years. Since the current eruption began in 1955, the longest quiet period prior to this was 307 days from April 1971 until March 1972.

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.

Information Contacts: JMA.