The symmetrical Kronotsky stratovolcano lies between the Pacific Ocean and Lake Kronotsky, Kamchatka's largest lake. The lake formed during the late Pleistocene and early Holocene when extensive lava flows on the south side of Kronotsky volcano dammed the Listvenichnaya River. The flanks of the massive volcano are dissected by radial valleys up to 200 m deep. A volcanic neck plugs the summit crater. Cinder cones are found on the north and primarily on the SE and SW flanks. Kronotsky lavas have been dominantly basaltic, with the exception of the small basaltic andesite summit lava extrusion and a flank lava flow. Weak phreatic eruptions took place in the 20th century.