<p><strong>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 <a id="v92v" title="volcano" href="http://environment.nationalgeographic.com/environment/natural-disasters/volcano-profile/">volcano</a> off <a id="bshw" title="Indonesia" href="http://travel.nationalgeographic.com/travel/countries/indonesia-guide/">Indonesia</a>. <br></strong></p><p>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 <a id="u7-q" title="Sulawesi (map)" href="http://maps.nationalgeographic.com/map-machine#s=r&amp;c=-1.9764730799149242, 122.04495996236794&amp;z=5">Sulawesi (map)</a>.</p><p>Mining companies first spotted the Kawio Barat volcano in the 1990s with satellite altimetry. But "we were the first to go there with a [remotely operated vehicle] and actually discover hydrothermal fluids coming out of the volcano," microbiologist <a id="p7xl" title="Jim Holden" href="http://www.bio.umass.edu/micro/faculty/holden.html">Jim Holden</a>, chief U.S. scientist for the Kawio Barat expedition, said in an email.</p><p>(Watch <a id="jvq9" title="video of the giant Kawio Barat underwater volcano" href="http://news.nationalgeographic.com/news/2010/07/100714-indonesia-okeanos-volcano-exploration-vin/">video of the giant Kawio Barat underwater volcano</a>.)</p><p><em>—John Roach </em></p>