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an island in the central part of the Greater Kuril Chain, in Sakhalin Oblast, RSFSR. Simushir is 58 km long and 6-10 km wide; at the Kostochko Isthmus it narrows to 2.5 km. The island consists of a chain of volcanic domes joined by foothills. Active volcanoes include the Prevo (1,360 m), the Zava-ritskii Caldera, and the Goriashchaia Sopka. Major volcanoes that have recently erupted are the Mil’na (1,539 m) and the Uratman, whose enormous caldera is occupied by Broutona Bay. The slopes are covered with alder and birch krummholz, and the shore is occupied by a marine marsh with scattered dwarf Kuril bamboo. Simushir has one population center, Kitoboinyi.