Lamont’s Marie Tharp: She Drew the Maps that Shook the World

July 27, 2020

By Marie DeNoia Aronsohn

When oceanographer Bill Ryan first encountered Marie Tharp she was screaming, arguing with Ryan’s mentor, geologist Bruce Heezen. That was back in the fall of 1962 when Ryan had first arrived at what was then called the Lamont Geological Observatory as a graduate student. Tharp and Heezen were fighting over a map of the Indian seafloor. Tharp had followed Heezan’s instincts, realizing after weeks of work, that he was incorrect. Ryan witnessed the “seismic” moment.

marie tharp headshot

On the 100th anniversary of her birth, Marie Tharp’s grit and brilliance are as legendary as her work. Reproduced with permission from Marie Tharp Maps LLC and Lamont-Doherty Earth Observatory.

“She tore up this huge sheet she’d been working on for a month or so. And I thought, ‘Oh my God, this is science,’” said Ryan. He added with relish, “He was wrong, she was right.” So, began Ryan’s work and his part in a chapter of scientific history, working with and adjacent to Marie Tharp, now considered one of the great cartographers and pioneers of our time.

Tharp, who died in 2006, began working at Lamont in 1949. She was assistant to geologist Bruce Heezen. He was crisscrossing the oceans, gathering thousands of depth measurements by sending high-frequency sounds into the seafloor and recording the time difference of the return echo. This data came to Tharp on great rolls of paper. Tharp used the data points and deduced the rest, drawing from her vast knowledge of geology. In this way, she was able to draft maps of the seafloor. Lamont published her map of the northern Atlantic Ocean in 1957.

This map gave form, scale, and texture to an unseen, deep ocean topography, illuminating one of the planet’s most important mysteries. When published, this work represented a huge departure from what science understood about the seafloor and ultimately touched off one of the greatest paradigm shifts in earth science history. Tharp’s work, and that of her contemporaries, led to a period of discovery known as the plate tectonic revolution, which proved that Earth’s outer shell is divided into several plates that glide over the mantle, the hot, rocky inner layer above the core.

tharp's 1957 map of atlantic seafloor

Before Tharp and Heezen’s 1957 map of the Atlantic seafloor, scientists assumed the bottom of the ocean was mostly flat and featureless. Reproduced with permission from Marie Tharp Maps LLC and Lamont-Doherty Earth Observatory. (Note: This map is available as a Zoom background.)

After several decades of work, Tharp and Heezen published the first map of the entire world’s ocean floor in 1977. This world ocean map is considered an icon, and hangs on university walls throughout the world.

Before Tharp’s maps, much of the scientific community believed the ocean bottom was essentially featureless, a receptacle for settled sediments, shaped like the bottom of great big bathtub. In 1952 Tharp noted that each profile had a consistent notch at the crest of the mid-ocean ridge. She called it the “rift.” This discovery was evidence supporting the concept of continental drift, the theory that the Earth’s continents have moved over geologic time relative to each other, thus appearing to have “drifted” across the ocean bed. Science had rejected the theory decades earlier. The scientific community shunned those who believed in continental drift and were known as “drifters.” And, according to recordings of Marie, “to be a drifter could get you fired.”

But Tharp pushed on and showed that earthquake epicenters traced the same line as the rift itself. Applying this correlation to existing seismic data, in her drawings, she extended the rift to parts of the ocean where depth soundings were incomplete or absent. She extrapolated the rift into the south Atlantic, and on into the Indian Ocean, eventually linking it to the East African Rift Valley.

However, it was not until four years after she discovered the world-wide rift that Heezen agreed to publish this research. Tharp was given no credit for the work. The paper bore the names Heezen and Maurice Ewing, Lamont’s founding director.

Marie Tharp and Bruce Heezen sit in front of a world map of the ocean seafloor

Tharp and Heezen worked together for decades, with Heezen collecting ocean depth data and Tharp mapping his findings. Reproduced with permission from Marie Tharp Maps LLC and Lamont-Doherty Earth Observatory.

Ryan, who stepped in and helped Tharp complete the world map after Heezen’s sudden death in 1977, regarded Tharp as underappreciated and underutilized. He describes her as a flaming redhead with a wide smile. He says she was brilliant but acted as if she were “silly.” This, he said, was how she—one of the most influential cartographers in history—needed to present herself so she could navigate the social minefields. Women in the fifties and sixties were not welcomed as equals in the scientific research community—a fact that Ryan says led Tharp to affect the “mannerisms of a little girl, giggling and talking in a squeaky voice.”

Lamont interim director and climate scientist Maureen Raymo, the first woman to lead the observatory, said she’s pleased with the recognition Tharp is now receiving and feels confident she’d welcome the way Lamont has evolved since then.

“Marie Tharp would LOVE today’s vibrant, diverse Lamont and probably say, ‘It’s about time!’” Raymo said.

Despite Tharp’s girlish mannerisms, Ryan and the world would discover Marie Tharp was more mighty than meek—an excellent geologist with a fierce intellect.

Marine geologist Vicki Ferrini, a senior research scientist at Lamont, sees the connection between Marie Tharp’s revolutionary maps and Lamont’s present leadership in bathymetry mapping. Ferrini is part of a global collaborative effort to map the entire seafloor by the year 2030, called Seabed 2030.

“It was [Tharp’s] vision, her technical knowledge, and her artistry that really revealed things that had not yet been done and are still relevant, valid, and incredibly accurate today,” said Ferrini.

Last year Lamont climate scientist Suzana Camargo was named to a professorship created in Tharp’s honor, becoming the first Marie Tharp Lamont Research Professor.

“Marie Tharp’s life and scientific discovery are an inspiration to me,” said Camargo. Every time I see her famous seafloor map hanging on the walls of Lamont’s hallways, I’m reminded of her amazing accomplishments, tremendous talent, and how much she had to fight to be a scientist. It’s a pity that it took so long for her to be properly recognized. I think she would get a kick out of seeing all the comments on social media about her these days. She practically has her own fan club among the current generation of scientists, who are taking pictures posing as her, and buying mugs and t-shirts with her pictures and her famous map on them.”

As the 100th anniversary of Tharp’s birth draws near on July 30, Lamont and the Earth Institute are celebrating her life and legacy through a series of blog posts, webinars, and more. Follow along here.

Media Inquiries: 
Marie DeNoia Aronsohn
marieda@ldeo.columbia.edu
845-365-8151