On October 9, 1953, the research vessel Vema departed Woods Hole, Massachusetts, on the first of many expeditions that would map the floor of the Atlantic Ocean. On board was Marie Tharp, a geologist and cartographer who had been hired because the expeditions needed technical staff and many male scientists refused to sail with women, so she stayed on shore and did the analysis.

Tharp was born in 1920 in Ypsilanti, Michigan. She studied geology at the University of Michigan and Ohio State, completing a graduate degree in mathematics as well. She was hired at Columbia's Lamont Geological Observatory in 1948 by Maurice Ewing — one of the few institutions that would employ women in technical research positions.

She could not go on the research voyages because of a longstanding superstition in maritime culture that women on ships brought bad luck. She worked with the sonar depth data collected by her colleague Bruce Heezen, who went on the expeditions. The data was collected at sea; she plotted it in the laboratory.

In 1952, analyzing data from six traverses across the Atlantic, she identified what appeared to be a continuous rift valley running along the center of the Mid-Atlantic Ridge. She told Heezen. He called it "girl talk." She plotted it again. The rift valley was real, and its existence supported the theory of continental drift — then deeply unpopular in American geological science.

The 1977 map of the ocean floor she and Heezen produced is the most recognized map of the ocean floor ever made. Heezen died before publication. His name appeared first.