Report on Suwanosejima (Japan) — June 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 6 (June 1997)
Managing Editor: Richard Wunderman.
Suwanosejima (Japan) Ashfall in March and continued ash emissions in April
Please cite this report as:
Global Volcanism Program, 1997. Report on Suwanosejima (Japan). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 22:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199706-282030.
29.638°N, 129.714°E; summit elev. 796 m
All times are local (unless otherwise noted)
An ash column 500-600 m high above the summit resulted in ashfall starting at about noon on 24 March and continuing until the evening of the following day. Ash emissions on 16-17 April sent a column 500-700 m high. Seismicity was characterized by numerous B-type earthquakes in March (~50/month), and by volcanic tremors during April (~ 200/month).
Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
Information Contacts: Sakurajima Volcanological Observatory (SVO), Disaster Prevention Research Institute, Kyoto University, Sakurajima-cho, Kagoshima 89114, Japan; Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.