Many of our listeners learned about plate tectonics in grade school. It’s an accepted theory, which means we have found tons of evidence for its existence, even if we can’t physically pull apart the Earth and see the plates and their layers directly. We’ve built up a veritable mountain of data with fossil records, seafloor spreading, earthquakes, and volcanoes. It’s a standard in geology lessons.

But it wasn’t always this way. In fact, some of you might be surprised to learn that plate tectonics wasn’t scientifically accepted by much of the geology community until the late 1960s, and it was proposed by Alfred Wegener back in the early 1900s. He proposed a hypothesis of continental drift and named a previous supercontinent Pangaea. And he was widely criticized and considered a bit of a crank, but his work started a debate in the field that stagnated with little evidence in his favor.

That all changed in the 1950s when the advancement of sonar technology during World War II led to large-scale mapping of the Atlantic Ocean’s seafloor. Enter Marie Tharp, one of my heroes, who was in the right place and the right field at the right time to advance the cause of continental drift in a big way.

Marie Tharp was born in 1920. Her father was a surveyor who made maps, and she frequently went out into the field with him. In 1941, she was attending Ohio University, and Pearl Harbor was attacked, bringing the United States into World War II and essentially removing all the young men from the workforce. To keep programs up and running, many university departments opened their doors up to women, finally, and Tharp jumped at the chance to join the geology department. She earned her first master’s degree in 1943 and the second one in mathematics from the University of Tulsa several years later.

Tharp loved fieldwork, but it wasn’t open to women, especially on the open seas, where all of this new sonar scanning was being done. She moved to New York and took a job at Columbia University as a “draftsperson assisting male graduate students working toward a degree in geology that she had already earned.” It was a job, and it was in her field. When Columbia founded the Lamont Geological Observatory, Tharp was offered a position working with geologist Bruce Heezen, who worked with all that wonderful oceanic data coming in. Tharp was his analyst and mapper.

That’s where this story goes from good to amazing. Tharp was analyzing the data from scanning strips done of the Atlantic Ocean, and she noticed something interesting. Not only was there a ridge running down the middle of the ocean, which people had noticed in the years prior, but there was a notch at the top of the ridge in each profile. Tharp thought this might be evidence of molten material coming up from below the crust and forming new land; evidence that could support this wild theory of continental drift that was still being debated.

By 1957, Tharp and Heezen had created an extensive physiographic map of the Atlantic basin, clearly showing the mid-Atlantic ridge. At the same time, Heezen was collecting data to help Bell Labs lay transatlantic cables, and he found that earthquakes clustered along the rift valleys Tharp had found. The combination of the maps and the earthquakes helped solidify the idea that the crust was being pulled apart along the ridge.

Around the time the theory of plate tectonics finally was accepted, Tharp and Heezen were asked to work with Austrian painter Heinrich Berann on ocean illustrations. They produced maps that were published in National Geographic as huge supplements between 1967 and 1971. Then in 1973, the U.S. Navy gave them a grant to do the same for the oceans around the globe, and that work produced the map seen at our website, DailySpace.org, which was finished in 1977 [Ed note: The map, not the website].

Unfortunately, Heezen died suddenly of a heart attack while in a submarine exploring the ridge near Iceland, and Tharp’s work dried up almost immediately. Like most women of her time, she went uncredited for a lot of the papers her data was included in, although her name is on the maps she helped produce.

Tharp received numerous awards later on in life, in recognition of her contributions to the fields of geology and mapping and plate tectonics. She died of cancer in 2006, but by all accounts, she was incredibly satisfied with the life she led. In fact, she said in 1999: I thought I was lucky to have a job that was so interesting. Establishing the rift valley and the mid-ocean ridge that went all the way around the world for 40,000 miles — that was something important… You can’t find anything bigger than that, at least on this planet.

Thank you, Marie Tharp, for your amazing work and your inspiration.

More Information

Science News article (Marie Tharp)

Science News article (Theory of Plate Tectonics)