Background2 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
See also: Sentinel hub | Landsat 8