Sonar Survey Spies Mysterious Plume Off California Coast

An oceanographic survey has discovered a 1,400-meter-tall plume rising from the seafloor off the coast of California. Water samples taken at the site, about 32 kilometers northwest of Cape Mendocino, indicate that the feature isn’t mineral-rich water spewing from a hydrothermal vent, but researchers aren’t yet sure exactly what the feature is made of.