When the rocky mound lurched onto his computer screen aboard the R/V OGS Explora, geophysicist Emanuele Lodolo couldn’t believe his eyes. Just four miles off the coast of Sicily, the team had stumbled on a previously unknown volcano with an old lava flow trailing some 2.5 miles westward across the seafloor.

“We were quite surprised about this, because we were really very close to the coast,” says Lodolo, a researcher at Italy’s National Institute of Oceanography and Experimental Geophysics.

The edifice, named Actea, is one of six volcanoes recently discovered while scientists were mapping the underwater landscape of the Sicilian Channel, a heavily trafficked waterway off the southwest coast of the island. While Actea is the closest to shore, the