Report on Suwanosejima (Japan) — May 1977
Natural Science Event Bulletin, vol. 2, no. 5 (May 1977)
Managing Editor: David Squires.
Suwanosejima (Japan) Frequent explosions and considerable ashfall
Please cite this report as:
Global Volcanism Program, 1977. Report on Suwanosejima (Japan) (Squires, D., ed.). Natural Science Event Bulletin, 2:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197705-282030
29.638°N, 129.714°E; summit elev. 796 m
All times are local (unless otherwise noted)
Frequent explosions from the summit crater occurred 26-29 April (table 1). Considerable ash fell nearby from eruptive clouds that rose 3,000 m above the vent. Explosion sounds and air shocks were often detected and glow was seen on one or two occasions.
Geological Summary. 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 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: JMA, Tokyo.