The circular, 5.5-km-wide island of Baluan in the Admiralty Islands is formed by a Pleistocene stratovolcano with a large summit crater and several flank vents. Some of these might be of Holocene age (Johnson 1990, pers. comm.). In contrast to its neighboring islands to the north, Baluan has erupted basaltic rather than rhyolitic rocks. Sabroma, the elliptical summit crater, has a maximum width of about 1 km. The arcuate rim of the Batapona Mountain pyroclastic cone is prominent at the north edge of the island. Several small islands consisting of cone remnants are located within a kilometer of the north coast. Warm springs occur along the coast. The only reported activity is an uncertain description of a submarine eruption near the island in 1931.