Skip to main content
EGU Award Ceremony (Credit: EGU/Foto Pfluegl)

Portrait Marie Tharp

EGU logo

European Geosciences Union

Marie Tharp

Image of Marie Tharp
Marie Tharp

Marie Tharp studied geology at the University of Michigan, where an accelerated geology degree offering a job guarantee in petroleum industry upon graduation was created in 1942. This program had been especially designed for the needs of the oil industry and was intended to attract women students, to compensate for the lack of young men who were sent to World War II. After obtaining her master's degree she was employed at the Stanolind Oil and Gas Company in Tulsa (Oklahoma). She considered her work there as “limited” and took night classes at the University of Oklahoma, thus completing a BSc in mathematics, with a final course in spherical trigonometry that served her in later years.

In 1948 Marie Tharp was desperately hoping to get a job in research at Columbia University, New York: ”If they had asked me to put seismographs on the moon instead of the bottom of the oceans I’d have agreed” she said. She was hired at Columbia and moved shortly after with the whole group of Maurice Ewing to the newly created Campus of Lamont Geological Observatory, where she stayed until her retirement, although until the mid-1960s she never became tenured. Tharp did not have a PhD and started as research assistant before being promoted to a research geologist, and later to a research scientist. Finally, in 1963 she became a research associate.

She worked on the mapping of the Ocean floors, in close collaboration with Bruce Heezen. Since women were not allowed to go on research vessels at that time, it was only in 1965 that Marie Tharp could participate to a data-collection expedition. Before that she specialized in the techniques of reduction and visualization of data that other colleagues brought back from research-vessel campaigns. She converted raw bathymetric data, from the numerical form, into profiles and maps, and developed the very successful technique of physiographic maps. Producing such maps required tedious calculations, but also a profound understanding of the structure and processes shaping the ocean floor, because large extrapolations and interpolations between the available sounding profiles needed to be performed.

In 1952, examining sounding profiles of the Atlantic, she noticed that they all show a V-shape at the center of the mid-ocean ridge and suggested that this structure corresponded to a rift valley. Her interpretation was not accepted by her colleagues and it was only in 1955 that these findings were published in an abstract, though without the name of Marie Tharp in the authors list. Only from 1959 onwards, after a decade of hard work on the structure of the ocean floor, she co-authored several significant publications, never being the first author. However, Bruce Heezen, in a tectonophysics paper of 1969, clearly acknowledged that she was the first to recognize the existence of “essentially continuous tectonically active median rift valleys along mid-ocean ridges”, both in the Atlantic and Indian Oceans. This result received many critiques, especially concerning the continuity of the latter structures based on large interpolations.

The major scientific achievement of Marie Tharp was the global mapping of the ocean floors, which brought her to the discovery of the axial valleys along the mid-ocean ridges, and their meaning as extensional tectonic structures. These findings together with her accurately mapped fracture zones, were fundamental steps towards the formulation of the theory of Plate Tectonics. The work Marie Tharp and Bruce Heezen had devoted their life to, was magnificently synthetized by the 1977 publication of the “World Ocean Floor Panorama”, which visualizes large-scale features as well as an immense number of details of the Ocean floors that have proven until today to be precisely mapped.

Image credit: Lamont-Doherty Earth Observatory and the estate of Marie Tharp.