Marie Tharp, oceanographic cartographer, and her contributions to the revolution in the Earth sciences

Abstract

In the early 1950s, two American geologists, Bruce Charles Heezen (1924–1977) and Marie Tharp, began mapping the sea floor to improve understanding of ocean-basin geology and to connect the oceans to the continents theoretically. Both were researchers at the Lamont Geological Observatory of Columbia University, now Lamont-Doherty Earth Observatory. Heezen and Tharp used the 'physiographic mapping' technique, which makes it possible to relate topographic features to underlying geology. The diagrams mostly utilized light and texture, rather than colour, and were sketched using a hachuring technique. Heezen collected data for research purposes and Tharp used his information to compile their physiographic diagrams. During this process, she confirmed previous predictions when she made an important discovery: a rift on the Mid-Atlantic Ridge. Tharp's visual interpretations of the sea-floor data contributed to the reintroduction of continental drift theory and the 1960s geological revolution. At a time when most women were excluded from scientific careers, Tharp, initially a research assistant, succeeded in this competitive arena. Working with Heezen as a geologist and cartographer, she had an unusual opportunity to participate in the era's exciting discoveries; and her contributions were acknowledged. While their data-gathering activities and analyses stimulated change and contributed to the revolution in the Earth sciences, Heezen and Tharp were not directly involved in the plate-tectonics revolution, but favoured expanding-Earth theory.