Long-term eruptive activity at a submarine arc volcano

Bubbling under Three quarters of the Earth's volcanic activity takes place beneath the oceans. We rarely know when and where eruptions occur, and most observations have been indirect, made from surface vessels or after the eruption had ended. Now Embley et al. report direct observations and sampling of an active eruption at a submarine arc volcano in the Northern Mariana Islands northeast of Guam. Remote-controlled submersibles were used first to identify an active hydrothermal plume at a depth of 540 metres near the summit of a recently mapped submarine volcano. Then volcanic activity was monitored in March 2004 and October 2005. Long-term eruptive activity has produced an unusual chemical environment and an ecosystem perhaps distinctive of active arc and hotspot volcanoes.