Barred from research ships, Marie Tharp mapped the ocean floor from a desk
Women were not allowed aboard research ships, so Marie Tharp worked from depth soundings brought back by male colleagues. In 1952 she spotted a valley running along the spine of the Mid-Atlantic Ridge. Her partner dismissed it as girl talk, until earthquake data proved the sea floor was splitting apart.
Tharp arrived on July 30, 1920, in Ypsilanti, Michigan, as the sole child of a language teacher and a government soil surveyor. Tagging along on her father's fieldwork gave her an early feel for maps, and constant moves meant she passed through more than 17 schools. She graduated from Ohio University in 1943 in English and music, then took advantage of wartime vacancies: Michigan's geology programme, closed to women until then, gave her a master's degree in 1944.
An oil company in Tulsa let her handle maps but never go into the field, so she earned a mathematics degree on the side. In 1948 she joined Maurice Ewing's Lamont Geological Observatory in New York as a draftsperson, without mentioning her geology degree, and began working with Bruce Heezen. For 18 years he gathered depth data aboard the ship Vema while she turned the numbers into pictures.
Lining up about six profiles across the North Atlantic, she found a V-shaped notch running continuously along the ridge's crest and suspected a rift where crust was being pulled apart. That idea backed continental drift, which Heezen then thought impossible. It took about a year, and a separate map of undersea earthquake centres plotted by Howard Foster, before he saw the quakes lined up with her valley. She went on to trace similar rifts into the South Atlantic, the Indian Ocean and the Red Sea, pointing to a globe-circling system.
Cold War rules forbade publishing contour maps of the sea floor, so the pair drew realistic landscape-style views instead, releasing a North Atlantic map in 1957 and, with painter Heinrich Berann, the whole World Ocean Floor in 1977. Her name was missing from key plate tectonics papers of 1959 to 1963, and after a feud Ewing fired her in 1964. Recognition arrived late: the Library of Congress ranked her among the four greatest cartographers of the century, a lunar crater bears her name, and she died on August 23, 2006, aged 86.
Source: Marie Tharp
