Vast seabed chasms are carved by riverlike processes
In April 2003, scientists on the German research vessel Meteor were cruising toward a site off the arid northwestern coast of Africa. On a mission to examine the erosion that sculpts the ocean floor, the crew was anxious to reach the study site to focus the ship's seafloor-scanning sonar on an area where they knew undersea landslides had occurred. It's a good thing they turned their equipment on early. At least 150 kilometers short of their destination, the sonar revealed a previously unknown undersea canyon deep enough to swallow an 85-story skyscraper.