Dietz, Robert Sinclair

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(b. Westfield, New Jersey, 14 September 1914;

d. Tempe, Arizona, 19 May 1995), marine geology and geomorphology, plate tectonics, planetary science.

Widely known for pioneering contributions to the geology of the seafloor and to geological aspects of the theory of plate tectonics, Dietz also made important scientific contributions to the recognition of impact structures, particularly of ancient, eroded impact scars on Earth, which he named astroblemes(star wounds). He also contributed to and used new methods of seafloor exploration, including scuba and bathyscaph. Dietz published prolifically in scientific and popular scientific journals and was both a synthesizer of key research and a generator of controversial speculation.

Early Life . Robert Sinclair Dietz was the second youngest of seven children (the eldest a girl, then six boys); his father Louis was a civil engineer and his mother Bertha a devout Christian Scientist. Dietz reminisced that by high school he had rejected all religion, developed a serious interest in science, and become an ardent amateur naturalist and rock hound; his interest in astronomy, and especially the Moon, commenced at this time. Dietz’s mother died when he was in high school, and his father died a few years later.

In 1933, Dietz hitchhiked west from New Jersey to the University of Illinois, attracted by the Chicago World’s Fair and cheap tuition. Dietz intended to major in geology and to pursue his interests in astronomy at Illinois, although its astronomy department was weak at the time. He took the two available astronomy classes and studied every lunar photograph he could obtain. Dietz decided that lunar craters must be formed by meteorite impact and submitted a PhD proposal to study craters on the Earth and Moon. His professors, however, turned it down, steering Dietz instead toward marine geology.

On the Illinois geology faculty was a first-generation marine geologist, Francis Parker Shepard, who conducted research in the summer at the Scripps Institution of Oceanography in La Jolla, California. Dietz befriended fellow student K. O. (Kenneth Orris) Emery, and together they were Shepard’s first two graduate students, both going on to prominent careers. For his MS degree (1938), Dietz studied phosphorite deposits off the coast of southern California, and for his PhD (1941) degree he examined deep-sea clays. Dietz spent a good portion of his graduate student years at Scripps and some time at the Smithsonian Institution in Washington, DC, as well.

Career . Once graduated from Illinois with his PhD, Dietz returned to Scripps and applied for work with the navysponsored Division of War Research in San Diego. However, he had enrolled in the ROTC at Illinois and was already a first lieutenant in the U.S. Army Reserve, so the navy would not hire him. Instead, in August 1941, he was called to active duty as a ground officer in the U.S. Army Air Corps. After Pearl Harbor, he applied for and went through flight training, serving thereafter as an instructor in Hondo, Texas, for about eighteen months and then transferring to a photographic mapping squadron. Most of his photo-mapping work was in South America, where he was fascinated with aerial views of Earth.

During the 1940s, Dietz worked on papers interpreting lunar craters and certain ancient circular structures on Earth as impact features. While based in Texas, Dietz flew repeated proficiency and recreational flights to Meteor Crater, a 183-meter (six-hundred-foot) deep depression in Arizona, which helped convince him that meteor craters existed on Earth. Contradicting the prevailing “cryptovolcanic” hypothesis for the origin of certain ancient circular structures on Earth, Dietz called them “cryptoexplosion” structures and used shatter cones as critical evidence for impact.

From the late 1930s through the 1950s, most of Dietz’s publications and reports focused on aspects of marine geology and technology. In 1946, Dietz joined the U.S. Navy Electronics Laboratory (NEL) in San Diego as a civilian scientist, becoming head of the Sea-Floor Studies Section; Henry W. Menard, hired in 1949 by this group, chronicled some of its history in his memoir, The Ocean of Truth(1986). Dietz worked with a wide range of marine geologists during this postwar exploratory oceano-graphic era, including a cast of leading oceanographers at NEL and Scripps.

Dietz’s first assignment at NEL was to lead the oceanographic research effort of Admiral Richard E. Byrd’s fourth and last Antarctic expedition, Operation Highjump, in 1946 and 1947. Dietz also co-led the Mid-Pacific (MidPac) expedition, sponsored by the navy and the Scripps Institution in 1950. Always looking for better ways to study the ocean floor, in 1952 he authorized the first U.S. purchase of “aqua-lungs,” invented by Jacques-Yves Cousteau and Emile Gagnan in France. NEL researchers and colleagues from Scripps then made the first offshore geological map of the seafloor using scuba gear. In 1953, Dietz was a Fulbright Fellow at the University of Tokyo, which inspired him to name the chain of mountains he mapped in the northern mid-Pacific after Japanese emperors—the Emperor Seamounts.

From 1954 to 1958, Dietz was assigned to the U.S. Office of Naval Research (ONR) in London as scientific liaison conducting overt scientific intelligence in western Europe, covering all earth sciences. During the London years Dietz began collaborating with Swiss engineer Jacques Piccard in developing the bathyscaphe Trieste for ultra-deep-sea diving. The collaboration culminated in 1960, when the Trieste dived seven miles, an experience described in their popular and widely translated book, Seven Miles Down(1961). During his London assignment, Dietz’s writing consisted primarily of technical reports on scientific meetings and on the status of science in various countries.

While in London, Dietz kept up with science in the United States and had a keen interest in developments regarding interpretation of continents and ocean basins and of the nature and topography of the seafloor. By 1958, at a meeting in France on the topography and geology of the deep sea, Dietz was entertaining the possibility of continental drift, was aware of accumulating evidence (some of which he had helped collect) that the seafloor was relatively young, and was cognizant of detailed descriptions of seafloor topography. Thus it should not be surprising that he and Harry Hammond Hess independently arrived at the idea of seafloor spreading (Dietz’s term) in the early 1960s.

Dietz returned in 1959 to the Navy Electronics Laboratory in San Diego, moved in 1963 to the U.S. Coast and Geodetic Survey in Washington, DC, and through a series of bureaucratic reorganizations ended his government service at the National Oceanic and Atmospheric Administration (NOAA) in Miami. Dietz formed a team of marine scientists at NOAA similar to the seafloor studies group at NEL. He also held several visiting professorship positions in the 1970s as he became disenchanted with his government position; Dietz felt that the “o” in NOAA was receiving less attention than the “a” and that his agency’s efforts in geology and geophysics were minimal. In 1977, he retired from government service and moved permanently to Arizona State University at Tempe, where he was professor of geology and then emeritus professor, remaining active until his death. Especially during his later years, he became deeply involved in the creation-evolution debate.

Scientific Contributions . Dietz made major contributions in three general areas of Earth and planetary sciences: marine geology and geomorphology; continental drift and plate tectonics; and planetary geology, particularly the study of impact structures. He traveled widely in the United States and around the world, was a keen observer, and had a gift for finding adventure. He was an independent and broad thinker who relished the discussion of ideas and who commonly recognized the significance of new concepts before their originators.

One of the first professional marine geologists, Dietz made significant contributions in mapping and interpreting the sea floor, particularly of the North Pacific and the Arctic basins, as well as the Hawaiian swell. He recognized the importance of diving technology, and with colleagues at Scripps and NEL, he helped map submarine fans (fan-shaped deposits at the mouths of submarine canyons) off California and contributed to early recognition of the significance of submarine canyons and turbidity currents. Dietz published important analyses of the geomorphic evolution of continental margins, and he later considered the geologic architecture of these margins.

As early as 1953, Dietz was thinking about how the Hawaiian chain of islands and seamounts might be moving on a “conveyor belt.” By 1958, he was entertaining ideas about continental drift, and in 1961, he published his pioneering concept of seafloor spreading, independently proposed by Hess. Dietz went on to analyze the long-term evolution of continents, especially of their boundaries with the ocean. With student and illustrator John C. Holden, he published several influential and widely cited papers on geological aspects of plate tectonics, the most famous being their geological reconstruction of the ancient supercontinent of Pangea.

From his days as a student, Dietz thought of Earth in a planetary sense and commonly compared Earth with its Moon, speculating on why they looked so different when they should have had a shared history. An early proponent of the idea that the Moon’s craters were impact-generated rather than volcanic, Dietz expected such craters to have been formed also on Earth. However, he noted, Earth is geologically active and has an ocean and atmosphere, so these craters would have been eroded, deformed, and recycled. Certain ancient circular structures on Earth had characteristics that Dietz, along with a few other renegades, assigned to impact rather than volcanism. In this field, he is best known for having interpreted the Sudbury structure in Canada as a deformed and eroded impact structure.

Earth scientists and historians of science have noted that the second half of the twentieth century featured two major conceptual shifts in Earth sciences. The better known is the plate tectonics revolution, in which Dietz played a significant role. The second is the birth of planetary geology—the shift in viewing the Earth from an Earth-bound perspective to seeing it as a planet in a planetary system, and Dietz was involved here as well. Moreover, he was an important proponent of the scientific view that catastrophes are a natural part of Earth’s history. Dietz spent a good part of his time in later years refuting creationist views, co-authoring Creation-Evolution Satiricon(1987) with John Holden and even offering a monetary reward for solid evidence of Noah’s Ark.

Among many honors for his diverse contributions, he received the American Geophysical Union’s Bucher Medal (1971) and the Geological Society of America’s Penrose Medal (1988). Moreover, an Antarctic mountain, a Pacific seamount, and a Phoceaid asteroid have been named in his honor.


For unpublished documents pertaining to Dietz, see Robert Sinclair Dietz Papers, 1905–1995, Archival Collection MC 28, Scripps Institution of Oceanography Archives, University of California, San Diego. An online catalog of the collection is available at


“The Meteoritic Impact Origin of the Moon’s Surface Features.” Journal of Geology 54 (1946): 359–375.

“Geomorphic Evolution of Continental Terrace (Continental Shelf and Slope).” Bulletin of the American Association of Petroleum Geologists 36 (1952): 1802–1819.

“Shatter Cones in Cryptoexplosion Structures (Meteorite Impact?).” Journal of Geology 67 (1959): 496–505.

“Astroblemes.” Scientific American205 (1961): 50–58.

“Continent and Ocean Basin Evolution by Spreading of the Sea Floor.” Nature 190 (1961): 854–857.

“Vredefort Ring Structure: Meteorite Impact Scar?” Journal of Geology 69 (1961): 499–516.

With Jacques Piccard. Seven Miles Down: The Story of the Bathyscaph Trieste. New York: Putnam, 1961.

“Collapsing Continental Rises: An Actualistic Concept of Geosynclines and Mountain Building.” Journal of Geology 71 (1963): 314–333.

“Wave-base, Marine Profile of Equilibrium, and Wave-built Terraces: A Critical Appraisal.” Geological Society of America Bulletin 74 (1963) 971–990.

“Sudbury Structure as an Astrobleme.” Journal of Geology 72 (1964): 412–434.

“Reconstruction of Pangea—Breakup and Dispersion of Continents, Permian to Present.” Journal of Geophysical Research 75 (1970): 4939–4956.

With John C. Holden. Creation-Evolution Satiricon: Creationism Bashed. Winthrop, WA: Bookmaker, 1987.

“Earth, Sea, and Sky: Life and Times of a Journeyman Geologist.” Annual Review of Earth and Planetary Sciences 22 (1994): 1–32.


Bourgeois, Joanne, and Steven Koppes. “Robert S. Dietz and the Recognition of Impact Structures on Earth.” Earth Sciences History 17 (1998): 139–156.

Menard, Henry W. The Ocean of Truth: A Personal History of Global Tectonics. Princeton, NJ: Princeton University Press, 1986.

Sorkhabi, Rasoul B. “Robert S. Dietz—An Appreciation.” Journal of the Geological Society of India44 (1994): 121–126.

Joanne Bourgeois

Dietz, Robert Sinclair

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Dietz, Robert Sinclair (1914–95) An American naval oceanographer, Dietz worked on magnetic anomaly patterns in the north-eastern Pacific, and in 1961 he coined the term sea-floor spreading for his theory that new ocean floor was created at ocean ridges. He also worked on lunar cratering, and recognized craters on Earth as being of meteoric origin.

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