The Bismarck Sea lies off the north coast of New Guinea. It is surrounded by volcanic islands, the largest being New Britain. The underlying Bismarck Microplate is caught between the Australian Plate, moving north, and the Pacific and Caroline plates, moving west. The northern islands of the archipelago arise from the subduction of the Caroline and Pacific plates, marked by the Manus Trench to the north. Volcanoes on the south side of the sea are currently more active, arising from the subduction of the Solomon Sea Microplate at the New Britain Trench. To the east of the Bismarck Sea lies the Ontong Java Rise. This submarine plateau is one of the world’s largest expanses of igneous rock. It is composed of flood basalts, some of which date back to 120 million years ago.