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Report on Fukutoku-Oka-no-Ba (Japan) — 18 August-24 August 2021


Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
18 August-24 August 2021
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2021. Report on Fukutoku-Oka-no-Ba (Japan). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 August-24 August 2021. Smithsonian Institution and US Geological Survey.

Weekly Report (18 August-24 August 2021)



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

All times are local (unless otherwise noted)

The Japan Coast Guard reported that the eruption at Fukutoku-Oka-no-Ba continued during 16-22 August. Gas-and-steam emissions continued to be observed from the center of the island on 16 August. The pumice raft that was first identified on 15 August had expanded to about 100 km to the WNW and was about 13 km wide. Brown discoloration was visible surrounding the new island, which had a variable shape but a consistent diameter of 1 km by 16 August.

A local fisherman in the Ogasawara Islands who was fishing in South Iwo Jima (5 km NNE) posted photos and videos on 17, 20, and 22 August that showed strong white gas-and-steam plumes rising above the volcano. On 20 August lightning was visible within the gas-and-steam plume. On 22 August the plume was observed during 0430-0630.

Geological Summary. 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.

Sources: Japan Coast Guard, Yutaka Kosugi