A revolutionary 1957 thematic map of the North Atlantic Basin by geologists Marie Tharp and Bruce Heezen, which contributed greatly to acceptance of the theory of plate tectonics and continental drift.
The map depicts the North Atlantic Ocean and surrounding basin, including most of eastern North America, with landmasses in yellow and submerged regions in blue. Submarine and terrestrial topography is shown pictorially, with vertical relief exaggerated “about 20:1”. Whereas the popular imagination had long viewed the ocean floor as flat, muddy and nondescript, Heezen and Tharp’s map revealed its radically-varied topography, as dramatic as that of the terrestrial world.
For geologists, however, the stunning feature was the mid-Atlantic Ridge, clearly visible as a shallow “S” traversing the entire north-south extent of the map, and in particular the rift valley at its very center. The existence of this rift, when correlated by Tharp with separately-gathered evidence of strong seismic activity along its length, provided powerful evidence leading to the acceptance of A. Wegener’s revolutionary theory of continental drift, first posited decades earlier. When Heezen presented their findings at a 1957 lecture at Princeton, eminent geologist Harry Hess is said to have pronounced, “Young man, you have shaken the foundations of geology!”
The map was compiled from reams of echo-sounding data and drafted by Marie Tharp at Columbia University’s Lamont Geological Observatory. Though “just” a research assistant to Ph.D. student Bruce Heezen, it was Tharp who was first to recognize the mid-Atlantic Ridge, the rift, and their implications. The theory of continental drift was at the time controversial—so much so that adherence could break a young geologist’s career—and when Tharp first presented Heezen with her interpretation of the data he dismissed it as “girl talk”. Heezen finally came around after many months, when Tharp presented him with data demonstrating a concentration of seismic activity along the length of the rift, convincing evidence that it in fact marked the meeting point of two vast plates of the Earth’s crust.
The map accompanies “Oceanographic Information for Engineering Submarine Cable Systems”, an article by Heezen and C.H. Elmendorf in The Bell System Technical Journal for September 1957, examining “the application of the rapidly developing science of oceanography to the development and engineering of submarine cable systems” (p. 1093) This is to my knowledge the first publication of the map, and thus the first appearance of a systematic relief map of any region of the ocean floor. The map was republished in 1959 in Special Papers no. 65 of the Geological Society of America, in which Heezen, Tharp and Ewing describe their methodology.
As per plan, Heezen and Tharp followed this map with Physiographic Diagram of the South Atlantic Ocean, the Caribbean Sea, the Scotia Sea, and the Eastern Margin of the South Pacific Ocean (1961) and Physiographic Diagram of the Indian Ocean, the Red Sea, the South China Sea, the Sulu Sea and the Celebes Sea (1964). In 1977 the National Geographic Society published their capstone World Ocean Floor Panorama, painted by Austrian topographical painter Heinrich Berann.
Marie Tharp (1920-2006) and Bruce Heezen (1924-1977)
Heezen was born in Iowa in 1924 and received a B.A. from the University of Iowa in 1947. After being inspired by a talk by geologist Maurice Ewing, later his boss at Columbia, Heezen talked his way in to a job on the Wood’s Hole Oceanographic Institute’s research vessel Atlantis. He then followed Ewing to Columbia, where he received a Ph.D. in Geology in 1957. In addition to his and Tharp’s work on undersea topography, his research yielded important findings on submarine landslides and sedimentation, volcanism, and prehistoric impact events. Some writers accuse him of claiming the lion’s share of the credit for Tharp’s epochal discoveries, but in 1976, the year before his death, he wrote: “So over the last ten or fifteen years, what people think the bottom of the ocean looks like; that is, what most scientist and informed laymen think it looks like; is what Marie Tharp thinks it looks like.” (cited in North, p. 26)
Heezen died at sea of a heart attack in 1977, before he had had an opportunity to see the final printed version of his and Tharp’s capstone work, the World Ocean Floor Panorama. That year Antarctica’s Heezen Glacier was named after him, and in 1999 the U.S. Navy christened the research vessel USNS Bruce C. Heezen.
Tharp was born in Michigan in 1920, her mother a Latin teacher and her father a soil surveyor. After a peripatetic childhood in at least eight states and the District of Columbia, Tharp earned a B.A. in English from Ohio University. Though she had intended to teach, during World War II she was recruited into a geology program for women at the University of Michigan, at a time when male geologists were in short supply. Her first job, which she probably loathed, was a desk job with the Standolind Oil and Gas Company in Tulsa. In 1946 she married and in or around 1948 moved to New York City to be with her husband, though the marriage didn’t last.
There she got a job in the Columbia University Geology Department, then chaired by Maurice Ewing, and she and Heezen soon formed their three-decade research partnership. The roles were clearly delineated, with Heezen spending much of his time at sea gathering bathymetric data, and Tharp remaining at Columbia to compile and correct his raw data and translate it into the physiographic maps for which she is now famous (Women were for many years prohibited from working on research vessels, and it was only in 1968 that Tharp had an opportunity to participate in a research expedition.) Tharp retired from Columbia in 1983 and died in 2006 at her long-time home in the Hudson River town of Nyack, New York.
Later in life Tharp’s contributions began to be recognized, and she has been widely celebrated in the cartographic community. She received numerous awards, and from 1997-2007 one of her maps was featured in the Treasures of the Library exhibition celebrating the 100th anniversary of the Library of Congress’ Jefferson Building. In 2012 she received her own full-length biography, Hali Felt’s 2012. Soundings: The Story of the Remarkable Woman Who Mapped the Ocean Floor. Her vast archive, more than 40,000 items, is now at the Geography and Map Division of the Library of Congress.
In all, a landmark map by two of the greatest figures in 20th-century science and cartography.
Rumsey 6368. Background from Bruce C. Heezen, Marie Tharp and Maurice Ewing, “The Floors of the Oceans[:] I. The North Atlantic”, The Geological Society of America Special Paper 65 (1959); Gary W. North, “Marie Tharp and Her Ocean Floor Maps”, The Portolan, no. 79 (Winter 2010), pp. 20-27; Erin Blakemore, “Seeing Is Believing: How Marie Tharp Changed Geology Forever” published Aug. 30, 2016 at smithsonianmag.com; and Walter Sullivan, “Dr. Bruce C. Heezen, 53, Dies; Mapped Ocean Floors”, New York Times, June 23, 1977, p. 28 (all accessed May-June 2022).