Tharp, Marie, 1920–2006, American oceanographer and cartographer, grad. Univ. of Michigan (M.A. 1944). A geologist with experience in mapping, she came to Columbia Univ. as a geology research assistant in 1948, retiring in 1983. Painstakingly converting oceanographic soundings to physiographic maps of the North Atlantic Ocean floor, Tharp, working with Bruce Heezen, identified (1952) the Mid-Atlantic ridge and rift valley; when Heezen's group confirmed that seismic activity along the ridge was centered on the rift, it provided solid evidence of seafloor spreading and plate tectonics . Tharp and Heezen's work mapping the oceans ultimately led to the discovery of a 40,000 mi (64,000 km) panoceanic underwater ridge, made visible in their World Ocean Floor map published (1977) by the Office of Naval Research.
See biography by H. Felt (2012).
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