Dietz, Robert Sinclair

▪ 1996

      U.S. geophysicist and oceanographer (b. Sept. 14, 1914, Westfield, N.J.—d. May 19, 1995, Tempe, Ariz.), plumbed the ocean depths and set forth (1961) a theory of seafloor spreading, the process in which new crustal material continually upwells from the Earth's depths along the mid-ocean ridges and spreads outward at a rate of several centimetres per year. He later helped incorporate that theory into the broader, revolutionary concept of plate tectonics, which describes the Earth's surface as a mosaic of more than a dozen crustal plates in relative motion. Dietz also was noted for demonstrating that asteroidal and meteoritic impacts have been important geologic processes acting on the Earth and Moon for billions of years. He conceived and organized the manned deep-diving expedition to the Pacific Ocean's Challenger Deep in the bathyscaphe Trieste, the descent of which on Jan. 23, 1960, set a submarine depth record of 10,912 m (35,800 ft). Dietz was educated at the University of Illinois (B.S., 1937; M.S., 1939; Ph.D., 1941). During World War II he rose to the rank of lieutenant colonel in the U.S. Army Air Corps, and following the war he served (1946-54 and 1959-63) as a civilian scientist with the U.S. Navy. In this capacity he oversaw the oceanographic research on Adm. Richard E. Byrd's last Antarctic expedition (1946-47). Dietz was also associated with such organizations as the U.S. Coast and Geodetic Survey (1958-65) and the Atlantic Oceanography and Meteorology Laboratories (1970-77). From 1977 until his retirement in 1985, he served as professor of geology at Arizona State University.

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