More than two kilometres beneath the surface of the Pacific, off the coast of Oregon, an active underwater volcano has been hiding one of the strangest landscapes ever mapped on the seafloor. Using robotic vehicles capable of withstanding crushing depths, scientists from the Monterey Bay Aquarium Research Institute have spent more than two decades surveying Axial Seamount, a volcano along the Juan de Fuca Ridge that has erupted repeatedly since its discovery in the 1980s.