The island consists of a dormant stratovolcano, Pik Severgin -(; Japanese 春牟古丹岳; "Harikotan-dake"), which rises to above sea level. The peak is marked by two horseshoe shaped volcanic craters created by the collapse of the volcano's upper slopes. Other evidence of the collapse can be seen on the peninsulas to the east and northwest which were formed by the debris. The volcano has erupted occasionally from the 18th century onwards, with the last recorded eruption in 1933 sending volcanic ash as far away as Paramushir. The collapse of the cone resulted in a debris-avalanche which subsequently caused a tsunami, which killed two people on Pamamushir. The path on which the debris took is visible on satellite imagery.