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Report on Fukutoku-Oka-no-Ba (Japan) — April 1996


Bulletin of the Global Volcanism Network, vol. 21, no. 4 (April 1996)
Managing Editor: Richard Wunderman.

Fukutoku-Oka-no-Ba (Japan) Yellowish-brown discolored seawater seen again

Please cite this report as:

Global Volcanism Program, 1996. Report on Fukutoku-Oka-no-Ba (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199604-284130



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

All times are local (unless otherwise noted)

On 4 April, an aviator from the Japan Marine Safety Agency reported discoloration of seawater to yellowish brown at Fukutoku-Okanoba (BGVN 21:03). On 6 and 7 April, similar discoloration was observed by an aviator of the Maritime Defense Force. More discoloration was reported on 12 and 30 April. No floating pumice was observed. Discolored seawater has been seen on a smaller scale at this location, since 24 November 1995 (BGVN 20:11/12).

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: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.