Most of Earth’s volcanoes are in the oceans, yet scientists know very little about them compared to volcanoes on land. Schmidt Ocean Institute’s research vessel Falkor recently completed a 41-day expedition near Tonga, using cutting-edge technology to map, view, and sample underwater volcanoes while sharing observations with the public using real-time video streaming and chat programs. Findings include detecting widespread evidence of deep sea explosive volcanism, observing one of the rarest volcanic rock types on Earth, exploring the largest known dacite lava flow on our planet, and discovering three new hydrothermal venting sites.