Tharp, Marie

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 spreadingseafloor spreading,
theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges. First proposed in the early 1960s by the American geologist Harry H.
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 and plate tectonicsplate tectonics,
theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
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. 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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