Ewing, (William) Maurice (1906-1974)

US geologist whose studies of the ocean floor provided crucial data for the plate-tectonics revolution in geology in the 1960s. He demonstrated that midocean ridges, with deep central canyons, are common to all oceans. Ewing was born in Lockney, Texas, and studied at the Rice Institute in Houston. He developed his geological interests by working for oil companies. In 1944 he joined the Lamont-Doherty Geological Observatory, New York. From 1947 he was professor of geology at Columbia University, while also holding a position at the Woods Hole Oceanographic Institute. Using marine sound-fixing and ranging seismic techniques and pioneering deep-ocean photography and sampling, Ewing ascertained that the crust of the Earth under the ocean is much thinner (5-8 km/3-5 mi thick) than the continental shell (about 40 km/25 mi thick). His studies of ocean sediment showed that its depth increases with distance from the midocean ridge, which gave clear support for the hypothesis of sea-floor spreading.