It has 7.5 km wide caldera formed during a catastrophic eruption less than 10,000 years ago (reported ages range from 5,550 to 9,400 Before Present).

Krenitsyn Peak has a summit crater 350 m wide and is the highest point of the volcano and on the entire Onekotan Island.

Another caldera, Nemo Peak, lies at the northern end of the island, and it also contains a central cone and crater lake.

The caldera forming eruption yielded about 50–60 cubic kilometres (12–14 cu mi) of material and destroyed the upper parts of the pre-existing volcano.

[3] The caldera forming eruption wiped out vegetation on southern Onekotan, and it took a long time for it to recover.