Marie Tharp, born in 1920 in Ypsilanti, Michigan, rode along with her father, a USDA soil surveyor, and attended more than 17 schools before he retired in 1931. Her mother died when she was 15. She changed majors every semester at Ohio University and graduated in 1943 in English and music, but when World War II emptied the classrooms, the University of Michigan opened its petroleum geology program to women and she earned a master’s in 1944. At Stanolind Oil in Tulsa she was kept from fieldwork, so she earned a mathematics degree on the side, and in 1948 she joined Maurice Ewing’s Lamont Geological Observatory at Columbia, hiding her geology degree to be hired as a drafter. Barred from research ships, she stayed in New York turning Bruce Heezen’s sonar soundings from the Vema into profiles of the seafloor.

In 1952 she spotted a continuous V shaped rift valley running down the Mid-Atlantic Ridge, evidence for continental drift. Heezen, who favored the expanding Earth hypothesis, dismissed it as girl talk until Howard Foster’s transparent map of earthquake epicenters, made to study cable breaking turbidity currents, lined up inside her valley. Cold War secrecy barred publishing exact depths, so they worked with painter Heinrich Berann on physiographic diagrams, leading to National Geographic’s 1977 The World Ocean Floor. Her name was left off the key plate tectonics papers of 1959 to 1963, and in 1964 Ewing fired her amid his feud with Heezen.

• She kept mapping from home in South Nyack, New York, paid through Navy contracts Heezen secured.
• In 1968 she finally sailed on a data collection expedition aboard the USNS Kane.
• The Library of Congress named her one of the four greatest cartographers of the 20th century in 1997.
• Columbia gave her its first Lamont-Doherty Heritage Award in 2001, and Google Earth added a Marie Tharp map layer in 2009.
• In 2023 the Navy announced a survey ship would be renamed the USNS Marie Tharp.