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Report on Submarine Volcano NNE of Iriomotejima (Japan) — March 1991

Bulletin of the Global Volcanism Network, vol. 16, no. 3 (March 1991)
Managing Editor: Lindsay McClelland.

Submarine Volcano NNE of Iriomotejima (Japan) High-frequency earthquake swarm; many felt shocks; no surface activity

Please cite this report as:

Global Volcanism Program, 1991. Report on Submarine Volcano NNE of Iriomotejima (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 16:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199103-282010.

Volcano Profile |  Complete Bulletin

Submarine Volcano NNE of Iriomotejima


24.57°N, 123.93°E; summit elev. -200 m

All times are local (unless otherwise noted)

A swarm of high-frequency earthquakes . . . began 23 January, peaked in February, and continued at high levels through mid-April. The press reported that more than 940 earthquakes had been recorded by 14 April. Epicenters were on the W coast (at shallow depth) where many shocks were felt daily. Tremor episodes were not recorded and surface activity was not observed on the island or the surrounding sea.

Geologic Background. The southernmost Ryukyu Islands volcano is a shallow submarine volcano NNE of Iriomote-jima island. It is located 20 km NNE of Iriomotejima and 35 km WSW of the northern tip of the island of Ishigakishima in an area with an estimated depth of 200-300 m. A major submarine eruption took place on 31 October 1924. It produced rhyolitic pumice rafts with an estimated volume of about 1 km3 that were carried by currents along both coasts of Japan as far north as Hokkaido. The largest pumice blocks exceeded 1 x 2 m in size, and the volume of ejecta places this poorly known eruption among the largest in historical time in Japan.

Information Contacts: JMA.