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Report on Fukutoku-Oka-no-Ba (Japan) — September 1987


Scientific Event Alert Network Bulletin, vol. 12, no. 9 (September 1987)
Managing Editor: Lindsay McClelland.

Fukutoku-Oka-no-Ba (Japan) Discolored and spouting seawater

Please cite this report as:

Global Volcanism Program, 1987. Report on Fukutoku-Oka-no-Ba (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198709-284130



24.285°N, 141.481°E; summit elev. -29 m

All times are local (unless otherwise noted)

Discolored seawater continued to be seen in August by the JMSA. On 1 August, a zone of yellow-green seawater stretched 3 km NW-SE. The next day water over the vent was discolored green. Discolored water was next reported on 13 August, when cobalt-blue water covered an area of 0.01 x 4 km along an E-W axis. On 17 August the discolored area was 3 km in diameter, and spouting seawater was seen twice. No floating pumice was observed.

Geological Summary. Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the island of Minami-Ioto. Water discoloration is frequently observed, and several ephemeral islands have formed in the 20th century. The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986. The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.

Information Contacts: Y. Sawada, JMA; D. Shackelford, Fullerton, CA.