By far, most of the Earth's volcanic eruptions take place in the deep ocean. Until very recently, however, submarine eruptions had never been observed or studied. This spring, NOAA scientists returned to the Northern Marianas to document a continuous seven-year submarine eruption near Rota Island. In additiion, they studied the very deep (5250ft/1600m) eruption of Mata volcano off Tonga, capturing spectacular underwater lava bursts and gas explosions. Dr. Stephen Hammond, Chief Scientist of NOAA's Office of Ocean Exploration and Research, shares these exciting findings and discusses the physical, chemical and biological impacts of submarine volcanic activity.