In 1977, oceanographic cartographer Marie Tharp and geophysicist Dr. Bruce Heezen stunned the scientific community by publishing the first comprehensive map of the topography of the ocean floor. Tharp and Heezen drew the details by hand from thousands of ocean bottom soundings.

While working on the map, sponsored by the Office of Naval Research, Tharp discovered a rift valley at the peak of the Mid-Atlantic Ridge – a stretch of mountains running north-to-south through the middle of the Atlantic Ocean. Notably, the striking similarities between the shape of the ridge and the shape of the coastlines on both sides of the ocean contributed to a greater acceptance of the theory of continental drift.