Marie Tharp: The map that changed the world

"The tiny fringe of shallow sunlit waters which has been so frequently treated in books and films is entirely excluded, for in this book we are concerned only with the sunless and little-known abyss which claims over half of the planet."

HEEZEN & HOLLISTER (1971)

Marie Tharp was born July 30, 1920 in Ypsilanti, Michigan. Already at very young age she followed her father, a soil surveyor for the United States Department of Agriculture, into the field. However she also loved to read and decided to study literature at St John's College in Annapolis, but at the time women were not admitted to study there. So she went to Ohio University, where she graduated in 1943. 

The Second World War changed dramatically the situation in the United States - the nation needed highly educated replacement for the men who went into war, women now were encouraged to choose degrees also in science and technology. Marie enrolled in a petroleum geology programme, becoming so a "Petroleum Geology Girl" she graduated in geology in 1944. Afterwards she worked for a short time in the petroleum industry, however she found the work unrewarding and decided to resume her studies at Tulsa University. 

In 1948 she graduated in mathematics and found work at the Lamont Geological Laboratory of Columbia University. The atmosphere there was relaxed and friendly; also in times of Cold War money for geological projects studying the ocean floor, which results promised to be important for the war with submarines, was abundant. 

She began a prolific collaboration with geologist Bruce Charles Heezen (1924 -1977), who was specialized on the gathering of seismic and topographic data from the sea floor. As women Marie was not allowed on board of the research vessels crossing over the sea to collect profiles of the seafloor, so she started to calculate, interpret and visualize the data when Heezen was on the sea. She co-authored with Heezen a book and various papers; however her role was often neglected. Her employment despite continuous remained insecure, in certain moments the bureaucracy and financial troubles forced her to work from home. 

Between 1959 until the death of Heezen in 1977 she worked strenuously on various maps that would depict the still unknown topography of the oceanic basins - and the results were astounding. The ocean floor was not a flat plain of mud, as previously imagined, but displayed mountains, ridges and canyons, sometimes larger and deeper than any feature found on the continents. The most impressive feature however was a chain of mountains cutting in half the large basins of the oceans - Tharp and Heezen had discovered the backbone of earth, the Mid-Ocean Ridges.

Fig.1. "I was so busy making maps I let them argue,...[]" (photography published in HEEZEN & HOLLISTER 1971). Both Heezen and Tharp recognized the Mid-Ocean Ridges as spreading centres of the oceanic crust; both tended to consider this a result of an expanding globe. Marie Tharp´s cartographic accomplishments were exceptional because she overcame educational and employment barriers that limited opportunities for women of her generation. Without doubts she prepared the field for other researchers; however she will not became directly identified with the era's most revolutionary geological theory  - plate tectonics.

Bibliography:

BARTON, C. (2002): Marie Tharp, oceanographic cartographer, and her contributions to the revolution in the Earth sciences. In OLDROYD, D.R. (ed.) The Earth Inside and Out: Some Major Contributions to Geology in the Twentieth Century. Geological Society Special Publications 192, London: 215-228
HEEZEN, B.C. & HOLLISTER, C. D. (1971): The face of the deep. Oxford Univ. Press, New York, London, and Toronto: 659