THARP, MARIE

(b. Ypsilanti, Michigan, 30 July 1920;

d. Nyack, New York, 23 August 2006), cartography, sea-floor mapping, oceanography.

One of the most influential cartographers of the mid-twentieth century, Tharp created the first physiographic maps of the seafloor. These maps, made in collaboration with the geologist Bruce Heezen, were the first to reveal the detailed topography and multi-dimensional geographical landscape of the ocean bottom; they became significant evidence for the emerging theory of plate tectonics in the late 1960s. A research associate at Columbia University’s Lamont Geological Observatory for the first part of the career, Tharp worked as an independent researcher after the late 1960s.

Early Years. Marie Tharp was born in Ypsilanti, Michigan, the daughter of William Edgar Tharp, a soil surveyor for the federal Bureau of Chemistry and Soils, and Bertha Louise (Newton) Tharp, a teacher of German and Latin. Her father’s work caused the family to move frequently, and Tharp attended more than twenty different public schools in six states and the District of Columbia. After her father’s retirement in 1931, the family settled on a farm in Bell Fountain, Ohio, where Tharp graduated from high school. She subsequently enrolled in the University of Ohio.

Tharp had not decided on a major when she started college. Her father insisted that she pick a subject that she liked and that would offer her a way to earn her own living. While at Ohio, Tharp changed her major every semester, and might have decided to become a teacher had her mother not died before she graduated. She received her bachelor’s degree in English and music in 1943.

While she was finishing her degree at Ohio, Tharp happened upon a brochure from the University of Michigan’s geology program encouraging young women to apply for graduate training to prepare for positions in the petroleum industry. With classrooms empty of men during the war years, Michigan—which had never allowed women into its geology program—was trying to fill seats. Tharp jumped at the chance, graduated with a master’s degree in 1944, and went to work for Standlind Oil and Gas Company in Tulsa, Oklahoma, as a junior geologist. Upon her arrival, she discovered that women were not allowed to do field work, and so Tharp was stuck in an office coordinating maps and data for her male colleagues. During this time, she took enough courses at the University of Tulsa to earn a second bachelor’s degree in mathematics in 1948.

East to Columbia University. Four years in Tulsa left Tharp eager for a new challenge that would include research. She headed east to Columbia University and found a position as a research assistant to geology graduate student Bruce Heezen. Heezen worked under the direction of the eminent geophysicist W. Maurice Ewing. He became her close professional collaborator and the two worked together as a creative couple, a relationship that continued almost thirty years until Heezen’s death in 1977.

Her initial task at Columbia involved compiling oceanic bathymetry data. Prior to World War II, only widely scattered measurements had been made in the deep oceans, principally by government-sponsored expeditions such as those conducted by the British HMS Challenger(1872–1876) and the German Meteor (1925–1927). Although these expeditions had revealed certain large-scale features, including an extended rise called the Mid-Atlantic Ridge, the general characteristics of the seafloor remained largely unknown.

Interest in the oceans increased during and after World War II, owing to military concerns with understanding the ocean environment for anti-submarine warfare. By the early 1950s Heezen (now a junior PhD associate of Ewing at Columbia’s new Lamont Geological Observatory) and his colleagues began gathering wide-ranging data on the ocean floor, including its elevation. Tharp’s role at Lamont expanded to include assessing the reliability of past and contemporary depth measurements and interpreting the geographic landscapes they began to reveal. In the process Tharp made one of her most important discoveries: a rift valley bisecting the Mid-Atlantic Ridge that was structurally similar to the Great Rift Valley in Africa. Initially Heezen refused to accept this find, but relented after noticing that seismological records of undersea earthquake epicenters correlated with the mid-Atlantic rift valley. As precise measurements extended across Earth’s oceans, Heezen, Tharp, and Ewing also discovered that the Mid-Atlantic Ridge was part of a 40,000 mile long world-encircling ridge system, the largest tectonic feature on Earth’s surface and a significant geological finding.

Seafloor Cartography. In 1952 Heezen sought to make a detailed map of the North Atlantic seafloor, aware that existing maps were coarse and provided limited insight into distinct geographical provinces and landforms (including abyssal plains and mountain ridges) that depth soundings were revealing. He and Tharp decided against making a contour map in favor of a physiographic one, portraying physical features from an oblique perspective with scale and position carefully controlled. They did this for several reasons: beyond providing a realistic bird’s eye view, a physiographic map enabled them to circumvent navy classification policies because it did not provide precise depth data. By 1957, with support from telecommunications companies then laying the first transatlantic undersea telephone lines, Heezen and Tharp completed their pioneering detailed physiographic map of the North Atlantic Ocean seafloor, one of the most significant new maps of the twentieth century.

In the 1960s and 1970s Heezen and Tharp extended their mapping project to all the world’s oceans. Drawing on her artistic and drafting skills to create individual ocean basin maps, Tharp worked with Heezen and also the Austrian artist Heinrich Berann to produce the 1977 “World Ocean Floor” panorama, a widely circulated iconic map that depicted what was then known about seafloor topography. While these maps stimulated geophysical and oceanographic research—Heezen used the North Atlantic map to support the expanding Earth concept—the mapping project also exacerbated tensions between Heezen and Ewing involving publication credit and priority. In the late 1960s Ewing barred Tharp, who unlike Heezen did not occupy a tenured position, from working at Lamont, causing her to shift her mapping work to her nearby home.

Awards and Later Career. Tharp gained her first opportunity to go to sea in 1965 on a research cruise Heezen organized on Duke University’s R/V Eastward (at Lamont, Ewing still prohibited women from working at sea).

Largely invisible as a researcher early in her career, Tharp gained recognition for her geographic insights and cartographic skills later in life. She received awards from the Geography and Map Division of the Library of Congress and Woods Hole Oceanographic Institution, as well as the first annual Lamont-Doherty Earth Observatory Heritage Award in 2001. Four years later, Lamont created the Marie Tharp Visiting Fellowship program to aid promising women researchers.

After Heezen’s death, Tharp remained a professional map-maker, selling copies of the Heezen-Tharp seafloor maps from her research office-home in Nyack, New York, overlooking the Hudson River. Largely unfazed by the intense professional rivalry between Heezen and Ewing, Tharp was regarded by Lamont colleagues as intensely focused, wholly devoted to Heezen, and largely unconcerned with fashion or worldly pursuits. Tharp died of cancer in Nyack, New York, in August 2006.

BIBLIOGRAPHY

A collection of transcribed oral history interviews with Tharp resides at the Niels Bohr Library of the American Institute of Physics in College Park, Maryland. Her map collection is held at the Geography and Map Division of the U.S. Library of Congress.

WORKS BY THARP

With Bruce C. Heezen. “Physiographic Diagram of the North Atlantic.” Geological Society of America Bulletin 67 (1956): 1704.

With Bruce C. Heezen and Maurice Ewing. The Floors of the Ocean. Geological Society of America Special Paper 65. New York: Geological Society of America, 1959.

With Bruce C. Heezen. “Tectonic Fabric of the Atlantic and Indian Oceans and Continental Drift.” Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 258, no. 1088 (1965): 90–106.

With Bruce C. Heezen. “Physiography of the Indian Ocean.” Philosophical Transactions of the Royal Society of London, Series A: Mathematical and Physical Sciences 259 (1966): 137–149.

With Henry Frankel. “Mappers of the Deep: How Two Geologists Plotted the Mid-Atlantic Ridge and Made a Discovery that Revolutionized the Earth Sciences.” Natural History 95, no. 10 (1986): 49–62.

OTHER SOURCES

Barton, Cathy. “Marie Tharp, Oceanographic Cartographer, and Her Contributions to the Revolution in the Earth Sciences.” In The Earth Inside and Out: Some Major Contributions to Geology in the Twentieth Century, edited by David R. Oldroyd. London: Geological Society, 2002.

Doel, Ronald E., Tanya J. Levin, and Mason K. Marker. “Extending Modern Cartography to the Ocean Depths; Military Patronage, Cold War Priorities, and the HeezenTharp Mapping Project, 1952–1959.” Journal of Historical Geography 32 (2006): 605–626.

Ronald E. Doel
Kristine C. Harper