Mapping the Seafloor: In The Footsteps of Marie Tharp

It is hard to believe that the serious pursuit of mapping our submerged planet began just 60 years ago, marked by the publication of the first comprehensive map of any ocean basin by geologists and oceanic cartographers Marie Tharp and Bruce Heezen in 1957. Guest blogger and Caltech Ph.D. student in planetary science Meg Rosenburg shares a brief profile of Tharp’s work, and her key discovery which contributed to the reintroduction of the continental drift theory in the 1960’s.

Marie Tharp and Bruce Heezen

Marie Tharp and Bruce Heezen. (marie tharp maps)

In the work she is most known for Marie Tharp wielded a pen, but from her drafting table at the Lamont Geological Observatory in Palisades, NY, she could see the entire ocean floor.

“The whole world was spread out before me. I had a blank canvas to fill with extraordinary possibilities, a fascinating jigsaw puzzle to piece together: mapping the world’s vast hidden seafloor. It was a once-in-a-lifetime—a once-in-the-history-of-the-world—opportunity for anyone, but especially for a woman in the 1940s.” – Marie Tharp

Oceans cover most of the surface area of our planet, hiding a worldwide network of magnificent, rugged mountain chains where new crust is formed and pushed outward. Marie Tharp’s work revealed that world to us for the first time.

Having earned degrees in geology and mathematics, she moved to Columbia University’s Lamont Geological Observatory in 1948. Tharp quickly became responsible for organizing and compiling the ocean sounding data sent back by Bruce Heezen on his research voyages.

In 1952, Marie identified a key feature of the ridge dividing the North Atlantic: a V-shaped cleft running perfectly through its center. “I thought it might be a rift valley that cut into the ridge at its crest and continued all along its axis”. This was a controversial assertion during the decades-long debate over continental drift.

Six profiles based on soundings taken in the North Atlantic on cruises of Atlantis, 1952

Six profiles based on soundings taken in the North Atlantic on cruises of Atlantis, 1952.

Together, Marie and Bruce published the first physiographic map of the North Atlantic in 1957, and over the following 20 years extended their mapping to the rest of the world’s oceans.

While they never argued for continental drift, their maps and their interpretation of the ridges spurred the debate and prompted others to propose new mechanisms and theories. By the time Marie retired in 1983, plate tectonics had been widely accepted; she had witnessed – and helped to foster – a complete transformation in her field.

Heezen-Tharp North Atlantic Ocean Map

Physiographic diagram of the North Atlantic Ocean : by Bruce C. Heezen and Marie Tharp. 1968.

Read more about Marie Tharp in History of Geology: Marie Tharp: The map that changed the world by David Bressan and my original post on trowelblazers: Marie Tharp – the Woman who Mapped the Ocean Floor.

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