102 | Great Geologists
Marie Tharp
The impetus for the plate tectonics paradigm came in part from the discovery of the spectacular
geomorphology of the ocean floor from the 1940s onwards. At the center of these discoveries was
Marie Tharp, a pioneering oceanographer and geologist, who was largely responsible for generating
the first global map of the ocean floor and noting the rifted nature of mid-ocean ridges.
The geological map of England, Wales and part of Scotland, published by William Smith in 1815,
has been called “the map that changed the world.” But there is a more recent map that can rightly
make the same claim. Marie Tharp, in collaboration with her career-long colleague Bruce Heezen,
created the World Ocean Floor Map published in 1977. For the first time, in bright colour and a three-
dimensional rendition, the true scale of sea-floor topography was clearly illustrated. An inspiration to
scientists and armchair travelers, alike! The map was the product of thirty years of research led by
Tharp and Heezen, including discoveries that would provide critical impetus to the development of the
theory of plate tectonics.
Marie Tharp was born in Ypsilanti, Michigan in 1920. Her father was a soil surveyor for the US
Department of Agriculture and this led her to move around the country, such that she attended 24
different schools before attending college. Going into the field with her father doubtlessly inspired an
interest in maps, although it would take some time before this found an application in her career.
An avid reader, Tharp chose for her first degree a BA in English at Ohio University. Whilst there, she
decided to take a course in geology out of general interest. This led her to review her career options
and in 1944, she embarked on a Master’s degree in geology at the University of Michigan. The
programme was designed to attract women into the sciences by guaranteeing them jobs in the oil and
gas industry. Thus, the ten students in her class were called the “PG girls” (petroleum geology girls).
After a brief spell as a junior geologist with the US Geological Survey, Tharp went to work for
Standolind Oil and Gas in Tulsa, Oklahoma. Unfortunately, she found the office work unrewarding and
decided to undertake a further degree in mathematics at Tulsa University, graduating in 1948. She
then relocated to New York in search of a new career opportunity.
During the Second World War, the US Navy and its allies had collected a vast amount of bathymetric
data from the world’s oceans from numerous sonar surveys. After the war, this data became available
to the scientific community to study and augment with new data from research cruises. Analysis
of the data was conducted by the Lamont Geological Observatory of Columbia University (now the
Lamont-Doherty Earth Observatory) in New York, led by Maurice Ewing.
Tharp arrived at Columbia in 1948 as a drafting and computational assistant to Ewing’s graduate
students. One of these students, Bruce Heezen, had begun collecting Atlantic ocean-floor data in
1947. Since he was often away at sea, she soon took on the responsibility for collating, organizing and
eventually mapping data that he obtained. The two maintained a professional collaboration until his
death (aboard a submersible, whilst collecting data off Iceland) in 1977.