- VolcanoUshishur volcano in the central Kuriles has one of the world's most beautiful calderas, forming a almost complete ring rising above the sea. Most of the volcano's edifice is under water, but the submerged part forms 2 small islands. The southern island contains the summit caldera and the northern a portion of the volcano's flanks. The small 1.6-km-wide caldera of the southern island formed about 9400 years ago and has only a narrow breached on the south, allowing sea water to fill the caldera. Eruptions after the formation of the caldera formed small islands in the caldera bay.
Volcano type caldera normal or dormant Location Russia Summit elevation 401 m / 1,316 ft Ushishur volcano eruptions 1884, 1769, 1710 Typical eruption style explosive, lava dome building2 younger andesitic lava domes occupy part of the caldera bay. 2 other older domes are joined by a sand bar to the SE caldera wall. The 2 younger domes erupted sometime after the 1769 visit of Captain Snow to form islands in the bay.
A cluster of strong fumaroles and hot springs along the SE caldera shoreline was a sacred place to 18th- and 19th-century Kurile Ainu peoples. Vigorous submarine hydrothermal activity has modified the geochemistry of sea water within the caldera bay.
Aside from growth of the 2 younger lava domes, only minor phreatic eruptions have occurred at Ushishur during historical time.
Source: Smithsonian GVP Ushishur volcano information