a group of three small islands in the central part of the Greater Kuril Chain, between the Boussole and Urup straits. The islands of Chirpoi and Brat Chirpoev are separated by the Bystryi Strait, which is 2.7 km wide.
Chirpoi Island (area, 21 sq km) consists of four volcanic cones rising to a maximum elevation of 691 m. Two of the volcanoes are active: Chernyi has erupted in 1712 and 1713, 1854, and 1857; Snou, in 1879, 1960, and other years. The island is composed of andesitic basalts.
Brat Chirpoev Island (area, 20 sq km) is a chain of volcanic cones showing traces of recent activity and rising to a maximum elevation of 749 m. It is composed of basalts.
Morskaia Vydra Island, a rocky crag rising to an elevation of 150 m, is a volcanic dome.