Ambitle is a stratovolcano, reaching 450 metres (1,480 feet) above sea level. It last erupted in about 350 BCE based on radiocarbon dating. Its caldera, 3 kilometres (2 miles) wide, contains thermal areas on its western side. Venting of hydrothermal water also occurs in coral reefs to the west of this island.[1]
Pichler, Thomas; Dix, George R. (May 1996). "Hydrothermal venting within a coral reef ecosystem, Ambitle Island, Papua New Guinea". Geology. 24 (5). Geological Society of America: 435–438. doi:10.1130/0091-7613(1996)024<0435:HVWACR>2.3.CO;2.