History of Ambrym

caldera is the result of a huge plinian explosion, which took place around 50 AD. Its explosive force is rated 6, the second highest in the Smithsonian Institution's Volcanic Explosivity Index ranks of the largest volcanic explosions in recent geological history.

The massive, 1900-year-old, 12 kilometres (7.5 mi) × 8 kilometres (5.0 mi) caldera is the site of two active volcanic cones, Benbow and Marum (also spelled Maroum).

While at higher elevations cinder cones predominate, the western tip of the island is characterized by a series of basaltic tuff rings, of which the largest is about 1 kilometre (0.62 mi) in diameter. These were produced by phreatic eruptions when magma contacted the water table