The islands are mainly of volcanic origin.
Active volcanoes are present and earthquakes are frequent.
The low temperature, high humidity, and persistent fog make the islands unpleasant for human habitation. There are, however, communities engaged in sulfur mining, hunting, and fishing. The Yalta Conference ceded the islands to the USSR, and Soviet forces occupied the chain in Sept., 1945. Japan challenged the Soviet right to the Kuriles, and demanded the return of the four southernmost islands. The failure to resolve the impasse has remained a major stumbling block in Russo-Japanese relations in the second half of the 20th cent.