From Miller and others (1998) 
: "Carlisle Island consists of a single symmetric cone, 1524 m high and 6.5 km in diameter at sea level; its steep upper slopes are generally snow-covered year round. Little is known about Carlisle volcano's structure and composition. The topography suggests that the lower slopes of Carlisle are slightly more irregular in form and more dissected by erosion than are the uppermost slopes. According to Sekora (1973) 
, the western margin of the island consists of a small plateau at an elevation of 50 m, suggesting that the Carlisle stratovolcano is constructed on an emergent marine terrace."