A recently concluded expedition to explore seven submarine volcanoes in the Mariana Arc in the western Pacific Ocean made what is thought to be the first direct observation of a deep-sea volcano during an eruptive episode.

At a 13 May briefing in Washington, D.C., scientists with the National Oceanic and Atmospheric Administration described how an unmanned submersible, the Remotely Operated Platform for Ocean Science (ROPOS), dived into murky waters about one half of a kilometer below the ocean surface off of NW Rota 1 volcano.