Plate Tectonics and People

Robert S. Dietz

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Biographical Information                      

Robert S. Dietz was an American Geologist who was known for his substantial contributions to and for the promotion of Theory of Plate Tectonics.  Dietz was born in Westfield, NJ on September 14, 1941 and died in Tempe, Arizona in 1995.  Dietz was educated at the University of Illinois where he received his BS., MS. and Ph.D. in Geology.  Originally, Dietz wanted to study the surface of the moon for his dissertation but was told that there was no way to confirm his findings; instead he completed his work at the Scripps Institute of Oceanography in San Diego where he mapped the sea floor canyons off the coast of California.  

After completing his graduate work in 1941 , Dietz worked as a government scientist for thirty years.  At that time, marine geology was so young that academic positions where almost unheard of.  As a government scientist, Dietz could pursue questions of science that interested him because, working in government, no one was paying attention to what he published. According to Dietz, "science was simple then." This  resulted in substantial contributions made by Dietz to meteor impact theory as well as plate tectonics.  He worked in sea floor studies at the United States Navel Electronics Laboratory from 1946 - 1963 after which he took a position at the USCGS in Washington DC and then at the National Oceanographic and Atmospheric Administration until 1976.  He closed his career with a tenured position at the University of Arizona in planetary sciences.

Specific Contributions to Plate Tectonic Theory / Solid Earth Geophysics

During the 1950's and 1960's, Dietz was an advocate for both the motion of the sea floor and later Sea Floor Spreading, a term he coined in his 1961 Nature article entitled Continent and Ocean Basin Evolution by Spreading of he Sea Floor.   Both he and Harry Hess had simultaneously articulated very similar theories about sea floor spreading, however Hess is credited with idea because he distributed a preprint of his ideas the year before Dietz's paper was published which would ultimately become Hess's 1962 paper, History of the Ocean Basins. In addition, Hess had spent many years studying the Mid-Ocean Ridges, where Dietz had not.  

Both Hess and Dietz theorized new crust formation at the mid-ocean ridges and subduction of older crust at the trenches; the whole sea floor was moving outward from the mid-ocean ridges there by widening the sea floor.   Both stated that upwelling in the convection currents caused magma to reach the ocean bottom forming new rock and that downwelling of the convection currents dragged the sea floor downward at the trenches, thus holding the size of the Earth constant. Image of sea floor spreading 1

One important way in which Dietz's theory of sea floor spreading differed from Hess', was that Dietz correctly surmised that the lithosphere was moving on top of the plastic Asthenosphere with the convection currents, where as Hess suggested the the base of the crust was moving with currents. Dietz described the ocean floor as the "exposed and outcropping limbs of convection" (Dietz, 1961). Hess and Dietz also disagreed about the fracture zones that ran perpendicular to the ridges.  Hess thought that fracture zones were unrelated to the mid-ocean ridges; Dietz, meanwhile believed that the fracture zones were a result of uneven convection motion in the mantle thereby moving parts of the ocean floor at different rates.

Another way in which ideas of the two men differed was in the rock type being formed at the ridges: Dietz correctly thought it was basalt and Hess believed the rock was serpentine. Dietz felt that the merit in the theory that both he and Hess proposed was its ability to explain a plausible mechanism to support Continental Drift. 

Dietz's primary interests in plate tectonics were in the area of subduction and continental slopes as rift scars and and as prisms for accretion (wedge-shaped bodies of folded and faulted sea floor that abut a continental margin at areas of subduction or compression of plates). He found that guyots appeared tilted and were moving into the deep trenches of the Pacific Ocean. Dietz spent the early sixties, speaking about the 'Commotion under the Ocean' describing how sea floor spreading supported the idea of motionism and refuted questions about an expanding earth and the fixed sea floor, beliefs that were held by many scientists. 

Dietz's interest in a mobile sea floor began after he had been involved in the following findings:

  • There were few sediments on the sea floor compared with the continents.
  • In 1952 , Dietz, along with Menard, discovered fracture zones in the Pacific Ocean floor which led to his ideas about sea floor spreading. 
  • Image of the Pacific Fracture zones 2
  • The sea floor, based on fossil evidence, was much younger (Cretaceous as opposed to Cambrian) than the continents. This evidence was found by Hamilton, a graduate student working under Dietz at the Scripps Institute of Oceanography.
  • That guyots (flat-topped seamounts) were tilted toward and appeared be moving into the deep trenches.
  • In 1953, during his Fulbright Fellowship in Japan, he analyzed the Japanese-made soundings of the North Pacific where he mapped and named the Emperor Seamount chain which trace northwest from Midway to the Kamchatka Trench.  He noted in 1953 to fellow scientist, Robert Fisher, over lunch,  that this line of seamounts 'must be on some sort of conveyor belt.' 
  • Image of the Emperor Sea Mounts 3

Other Scientific Contributions

  • Dietz was the lead navy scientist who worked with Jacques Piccard on the bathyscaph Trieste, a "deep-diving blimp" (Dietz, 1994) that explored the ocean bottom of the Mariana Trench in 1960.
  • Image of the Trieste Bathyscaph 4
  • Dietz's most substantial contribution to science were his ideas about impact craters on Earth, which he referred to as Astroblemes.  He investigated circular structures on Earth that had long been held to be crypto volcanic and showed through his work investigating 'shatter cones' that the land features were impact craters. Dietz found that the Sudbury site in Canada was an 'astrobleme.'
  • Image of the Sudbury Basin 5
  • Contributed widely to the idea of catastrophic events in Earth's history.
  • Accompanied Admiral Byrd on his final expedition to Ant Arctica. 

Other Cool Stuff You Should Know

  • Dietz has three geologic formations named for him:  A mountain called Dietz Bluff in Antarctica; a tablemount in the Pacific and an asteroid (#4666-Dietz).
  • Brought the first scuba gear into Japan in 1953.
  • Dietz was an ardent evolutionist and was at loggerheads with creationists.  Late in his career, Dietz spoke out publicly against creationism.

Books written by R.S Dietz

  • With Jacques Piccard. Seven miles down: the story of the Bathyscaph Trieste. New York: Putnam, 1961
  • With John C. Holden. Creation-evolution satiricon: Creationism Bashed. Winthrop, WA: Bookmaster, 1987

Awards Earned:

  • Walter H. Bucher Medal of the American Geophysical Union for his work in the area of Plate Tectonics
  • God Medal of the Department of Commerce
  • Alexander Humboldt Prize
  • Penrose Medal of the Geological Society of America 
  • The Barringer Medal for his meteorite crater research


Dietz, RS. (1961) "Continent and Ocean Basin Evolution by Spreading of the Sea Floor." Nature 190: 854-516.

Dietz, RS. (1994) "Earth ,Sea and Sky: Life and Times of a Journeyman Geologist." Annual Review of Earth and Planetary Science 22: 1-32.

Frankel, HR. (2012) The continental drift controversy: introduction of sea floor spreading. Cambridge, UK: Cambridge University Press

Dietz, Robert Sinclair.Complete Dictionary of Scientific Biography. 2008. 15 Jun. 2013<>.

For the love of geology. Arizona State University. Retrieved from on 6/11/2013.

Robert Sinclair Dietz Biography. Retrieved from on 6/11/2013.

Commotion In the ocean: Lecturer gave his view of the bottom line. Retrieved from on 6/9/2013.