Captured by high-resolution cameras aboard a robotic submersible, mineral-rich water spews from hydrothermal vents in this June 30 picture of Kawio Barat, a massive undersea volcano off Indonesia.

During the past few weeks, the submerged volcano–one of the world’s largest–was mapped and explored in detail for the first time by a joint Indonesian-U.S. expedition north of the island of Sulawesi.