On 6 September, a Japan Maritime Safety Agency aviator reported yellow-green (in part yellowish brown) discoloration of seawater at Fukutoku-Okanoba over an area of 50 x 150 m, and to light green over a 300 x 500 m area. On 18 September green discoloration was seen by an aviator of the Japan Maritime Self-Defense Force. Smaller areas of discolored seawater have been seen at this location since 24 November 1995 (BGVN 20:11/12, v. 21, nos.1 and 3-5).

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, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan; Volcano Research Center, Earthquake Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html).