Geologist Marie Tharp (born 1920) is known for her maps of ocean floors. These maps are helpful in showing the structure and evolution of the sea floors.

Marie Tharp is a mapmaker who charted the bottom of the ocean at a time when little was known about undersea geology. Her detailed maps showed features that helped other scientists understand the structure and evolution of the sea floor. In particular, Tharp's discovery of the valley that divides the Mid-Atlantic Ridge convinced other geologists that sea floor was being created at these ridges and spreading outward. The confirmation of "seafloor spreading" led to the eventual acceptance of the theory of continental drift, now called plate tectonics.

Tharp was born in Ypsilanti, Michigan, on July 30, 1920. Her father, William Edgar Tharp, was a soil surveyor for the United States Department of Agriculture's Bureau of Chemistry and Soils; he told his daughter to choose...