Marie Tharp is the name of a scientist whose work, along with that of her colleague Bruce Heezen, opened the door that would trigger a revolution in our understanding of Earth.
Born in 1924, Marie was the daughter of a soil geologist who worked for the U.S. Department of Agriculture and who took Marie along with him as he conducted his research.
Marie was interested in the field work shared with her by her father but she was also interested in literature and wanted to attend St. John's College in Annapolis, where the curriculum consisted of the Great Books read in the original languages. However, St. John's was for men only and Marie instead attended and graduated from Ohio University in Athens, Ohio. Her graduation came in 1943 when U.S. had gone to war.
Men were off in the military, providing an opportunity for women to enter hitherto off-limits (to women) programs in science. She enrolled in a petroleum geology program at the University of Tulsa which she completed in 1944. She found the work "unrewarding" and continued her schooling at Tulsa, graduating in 1948 with a degree in mathematics and was hired by the Lamont Geological Laboratory of Columbia University. (Breeson, 2013)
The Lamont Laboratory was sending expeditions to sea to explore the unknown depths of the ocean.
The 1950s was, after all, the decade of the Cold War and the oceans were where American and Soviet submarines would perhaps do battle.
Marie, although a scientist, could not go on these expeditions.
She was a woman, don't you know! Everyone knew that a woman on board a ship, even a scientific research ship was "bad luck". Fortunately, she had a male colleague named Bruce Heezen with whom she collaborated from 1959 to his death in 1977.
Their collaboration was right at the center of a revolution in our understanding of the Earth.
The data from the research voyages showed something unexpected.
In 1947, The Atlantis, an oceanographic research ship from Wood's Hole had shown that there was a rise in the sea floor in the center of the Atlantic. It also showed that the sea floor, underneath the sediments, was composed of basalt. The continents in contrast are composed of granite. These facts opened the door to new explorations.
New explorations showed that the ocean wasn't simply a bowl filled with salt water, fish and whales. Instead it was not unlike the terrestrial world except more so. There were canyons, mountains, and ridges, often deeper, and higher than those found on Earth's surface.
Data collected by Bruce Heezen and put into a map by Marie showed that each of the Earth's oceans was divided by a ridge like that found in the Atlantic.
The map made by Marie showed that the ridges appeared to snake around Earth. The ridges portrayed on the map had an unusual feature: the rocks that composed the ridges were younger than those of the ocean floor and so are portrayed on the Tharp map as dark grey or black in contrast to the lighter shading of that of the surrounding sea floor. The conclusion drawn by Heezen and portrayed on the map was that sea floor was actually being created continually.
There is a similar geological structure in East Africa, called the Great Rift Valley. It appeared that there was a Great Rift Valley that snaked its way around Earth, called the "Great Global Rift" by Bruce Heezen in a 1960 article.
In 1912 Alfred Wegener had theorized that the continents had moved but his theory was crippled because he could not identify a mechanism to explain such movement.
The work of Bruce Heezen and other geologists that was portrayed by Marie Tharp's monumental map provided oceanographers with "an elegant, dramatic picture of the mid-ocean ridges running through the world's oceans like seams on a baseball. The map made sense in the framework of the young science of plate tectonics. " Subsequent investigators saw the mid-ocean ridges as places where oceanic plates are moving away from one another and new crust is formed by the upflowing of magma. As the crust moves, it cools and becomes more dense, contracts and sinks lower into the mantle, creating an ocean deeper than at the mid-ocean ridges. The oldest and densest crust subducts underneath the lighter continental crust. (Mervine, 2010)
The mostly unknown story of Marie Tharp reflects the changes in cultural attitudes over the past nearly seven decades. Attitudes that limited women and minorities to secondary roles in the sciences have slowly dissolved but are not completely gone.
Bresson, David (2013). July 30, 1920: Marie Tharp, the Woman who discovered the Backbone of Earth. Scientific American, July 30, 2013.
Burleigh, Robert and Raúl Colón (2016). Solving the Puzzle Under the Sea: Marie Tharp Maps the Ocean Floor. Simon & Schuster/Paula Wiseman Books. New York. (Recommended by the Library Journal for children in grades 2-4.)
Mervine, Evelyn (2010). A Famous Ociean Floor Map. Georneys: Geological Musings, Wanderings, and Adventures.
Tharp, Marie and Bruce Heezen (1977). World Ocean Floor Panorama. Marie Tharp Maps LLC, 8 Edward Street, Sparkill, New York 10976.
Dr. John Holton
Dr. John Holton joined the S²TEM Centers SC in July of 2013, as a research associate with an emphasis on the STEM literature including state and local STEM plans from around the nation.
S²TEM Centers SC is an innovation partnership managed by South Carolina’s Coalition for Mathematics & Science at Clemson University. Its purpose is to serve South Carolina by growing the Science, Technology, Engineering and Mathematics (STEM) possibilities and capabilities of learners and leaders.
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