Augustine Volcano is a central lava dome and lava flow complex, surrounded by pyroclastic debris. It forms Augustine Island in southwestern Cook Inlet in the Kenai Peninsula Borough of southcentral coastal Alaska, 280 kilometers (174 mi) southwest of Anchorage. Augustine Island has a land area of 83.872 square kilometers (32.4 sq mi), while West Island, just off Augustine's western shores, has 5.142 km2 (2.0 sq mi).The island is made up mainly of past eruption deposits.