Marie Tharp's discovery of the Mid-Atlantic Ridge showed that the seafloor was spreading, validating the theory of plate tectonics. She was an American geologist and oceanographic cartographer born #OTD in 1920. . . . . . . . . . #womeninscience #ocean #map #cartography #mapmaking #geology #tectonics #science #platetectonics #women #womancrush #sea #earth