U.S. geophysicist who made fundamental contributions to understanding of marine sediments and ocean basins, using seismic methods.

Studying the structure of the Earth's crust and mantle and making seismic refraction measurements in the Atlantic basins, along the Mid-Atlantic Ridge, and in the Mediterranean and Norwegian seas, Ewing took the first seismic measurements in open seas in 1935. He was among the geophysicists who proposed that earthquakes are associated with the central oceanic rifts that encircle the globe, suggested that sea-floor spreading may be worldwide and episodic in nature, and took the first deep-sea photographs (1939). A professor of geology at Columbia University from 1959 and director of the Lamont Geological Observatory from 1949, he collaborated with others in writing Propagation of Sound in the Ocean (1948), Elastic Waves in Layered Media (1957), and The Floors of the Oceans: I. The North Atlantic (1959).