Korovin, the most frequently active volcano of the large volcanic complex at the NE tip of Atka Island, contains a 1533-m-high double summit with two craters located along a NW-SE line.  The NW summit has a small crater, but the 1-km-wide crater of the SE cone has an unusual, open cylindrical vent of widely variable depth that sometimes contains a crater lake or a high magma column.  A fresh-looking cinder cone lies on the flank of partially dissected Konia volcano, located on the SE flank of Korovin.  The volcano is dominantly basaltic in composition, although some late-stage dacitic lava flows are present on both Korovin and Konia.