Report on Fukutoku-Oka-no-Ba (Japan) — 29 June-5 July 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 June-5 July 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Fukutoku-Oka-no-Ba (Japan). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 29 June-5 July 2005. Smithsonian Institution and US Geological Survey.
24.285°N, 141.481°E; summit elev. -29 m
All times are local (unless otherwise noted)
On the evening of 2 July, members of the Japan Coast Guard observed a steam plume rising ~1 km above the sea near the island of Minami-Iwo-jima. On 3 July, JMA confirmed that a small-scale eruption had occurred at the submarine volcano Fukutoku-Okanoba, prompting the Japan Coast Guard to issue a warning against sailing in the area. Observers saw rock and mud rising to the sea's surface near the volcano and a ~1-square-km area of water that had turned orange-brown. As of 4 July, a new island had not formed.
Geologic Background. Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the pyramidal island of Minami-Ioto. Water discoloration is frequently observed from the volcano, 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.