The eroded twin stratovolcanoes of Ostraya and Ovalnaya Zimina form a ridge north of the Udina complex at the SE end of the Kliuchevskaya volcano group. The larger Ovalnaya Zimina, on the W side of the complex, is capped by a large icecap and contains two summits. The extensively eroded Ostraya Zimina to the E has a sharp-peaked summit spire. A large debris avalanche from Ovalnaya Zimina traveled more than 10 km. No historical eruptions have occurred from these volcanoes.