is a group of volcanic rocks in the Philippine Sea about south of Tokyo and south-southeast of Aogashima, in the south portion of the Izu archipelago, Japan. The rocks were discovered by the French corvette ''Bayonnaise'' in 1850, while surveying the islands south of Tokyo Bay.


The rocks are the exposed portion of the western ridge of a submarine volcanic caldera, approximately in diameter at a depth of approximately .Christopher G. Newhall, Daniel Dzurisin: ''Historical Unrest at large Calderas of the World.'' Volume 1, U.S. Geological Survey Bulletin 1855, Washington 1988, p. 506
Bathymetric map around "Bayonnaise Rocks" based on Basic Map of the Sea
(1:50.000, retrieved 2012-12-13).
The above sea-level portion has a surface area of approximately 0.01 square kilometers, with a summit height of . and consists of three large rocks and many smaller rocks. The caldera is known to have erupted in 1869–1871, 1896, 1906, 1915, 1934, 1946, 1952–1955, 1957–1960, and 1970. The last known submarine eruption of the caldera was in 1988, which discolored the local water. On the northeast rim of the same caldera to the east of the Bayonnaise Rocks is a submerged reef named , which is a post-caldera cone with a depth of approximately . During a submarine volcanic eruption of 17 September 1952, an ephemeral island was formed, with a height of , which was created and destroyed several times by volcanic activity until completely disappearing on 23 September 1953. The following day, an eruption killed 31 researchers and crewmen aboard the Maritime Safety Agency survey ship No.5 Kaiyo-Maru. The island reappeared on 11 October, sinking again on 11 March 1954 and reappeared one more time between 5 April and 3 September 1954. Vegetation is sparse among the Bayonnaise Rocks. The islands are a resting place for migratory birds. Located in the Kuroshio Current, the area has abundant sea life, and is popular with sports fishermen.

See also

* Izu Islands * Desert island * List of islands


External links

* - Japan Meteorological Agency
Myojinsho: Global Volcanism Program
- Smithsonian Institution

- volcanolive.com {{Authority control Category:Izu Islands Category:Uninhabited islands of Japan Category:Volcanoes of Japan Category:Islands of Tokyo