The First Map of the Atlantic Ocean floor

Marie Tharp was an American geologist and oceanographic cartographer who, in partnership with Bruce Heezen, created the first scientific map of the Atlantic Ocean floor.

Tharp's work revealed the detailed topography and multi-dimensional geographical landscape of the ocean bottom. Her work included a more precise cartographic representation of the Mid-Atlantic Ridge and her discovery of the rift valley along its axis, causing a paradigm shift in earth science that led to acceptance of the theories of plate tectonics and continental drift.

She was born on July 30 1920, in Ypsilanti, Michigan, the only child of Bertha Louise Tharp, a German and Latin teacher, and William Edgar Tharp, a Soil Surveyor for the United States Department of Agriculture. She often accompanied her father on his field work, which gave her an early introduction to map-making. Despite this, she had no interest in pursuing a career in field work as during that time this was understood to be men's work.

Due to her father’s profession, she spent a good deal of her childhood travelling all over the United States, but when he retired the family moved to a farm in Ohio. After America’s entry into the Second World War many young men dropped out of schools and universities to join the armed forces. During the war, more women were recruited into professions like petroleum geology, normally restricted to men. Less than 4% of all Earth Sciences Doctorates at the time were obtained by women. Having taken a geology class at Ohio, Tharp was recruited to the University of Michigan at Ann Arbor's Petroleum Geology Program, where she completed a master's degree.

Together with the aforementioned Bruce Heezen, Tharp began to use photographic data to locate downed aircraft during World War Two and they eventually worked exclusively plotting the ocean floor. Due to the Cold War, these maps were kept secret because the US Government feared that the maps would be used by Soviet Submarines. Heezen collected bathymetric data aboard the research ship Vema, while Tharp drew maps from that data, since women were barred from working on ships at the time. She was later able to join a 1968 data-collection expedition. She independently used data collected from the Woods Hole Oceanographic Institution's research ship Atlantis, and seismographic data from undersea earthquakes. Her work with Heezen represented the first systematic attempt to map the entire ocean floor.

In 1952, Tharp painstakingly aligned sounding profiles from Atlantis, acquired during 1946–1952, and one profile from the Naval ship Stewart acquired during 1921. She created a total of approximately six profiles stretching west-to-east across the North Atlantic. From these profiles, she was able to examine the bathymetry of the northern sections of the Mid-Atlantic Ridge. Tharp identified an aligned, v-shaped structure running continuously through the axis of the ridge and believed that it may be a rift valley. She believed that the rift valley formed by the oceanic surface being pulled apart. Heezen was initially unconvinced as the idea would have supported continental drift, then a controversial theory. At the time many scientists including Heezen believed that continental drift was impossible. Instead, for a time, he favoured the expanding Earth hypothesis, dismissing her explanation as "girl talk".

Tharp and Heezen published their first physiographic map of the North Atlantic in 1957. Still, Tharp's name does not appear on any of the major papers on plate tectonics that Heezen and others published between 1959 and 1963. Tharp continued working with graduate student assistants to further map the extent of the central rift valley. Tharp identified that the rift valley extended along with the Mid-Atlantic Ridge into the South Atlantic, and found a similar valley structure in the Indian Ocean, Arabian Sea, Red Sea, and Gulf of Aden, suggesting the presence of a global oceanic rift zone. Subsequently, in collaboration with the Austrian landscape painter Heinrich Berann, Tharp and Heezen realized their map of the entire ocean floor, which was published in 1977 by National Geographic under the title of The World Ocean Floor. Although later recognized and attributed to for her work today on the Mid-Atlantic Ridge, it was Heezen, who at the time in 1956, put out and received credit for the discovery that was made.

The world needs to know about women like Tharp and many others, who were and continue to be ignored by their peers simply because of their Gender but who, nevertheless, have helped shaped current understanding of science, geography and the world and wider universe in which we live and we salute her remarkable achievements.