How one brilliant woman mapped the ocean floor’s secrets

 This animation by Rosanna Wan for the Royal Institution tells the fascinating story of Marie Tharp’s groundbreaking work to help prove Wegener’s theory.
Continental drift is common knowledge now, but when the idea was first proposed it was revolutionary.
Helen Czerski tells the story of how the maps of one of history’s finest cartographers shifted our view of the planet.

In the early 20th century, Alfred Wegener proposed a revolutionary idea: that the Earth’s continents were once joined together, and had gradually moved apart.

The idea contradicted almost everything scientists thought at the time, and it took the detailed work of a brilliant cartographer to prove him right.
Conventional ideas held that the ocean floors were flat, featureless planes.

As expeditions started to go around the world collecting ocean depth measurements, Marie Tharp – not allowed to join the expeditions herself – processed the data and began to craft detailed, revealing maps of the hidden ocean depths.
She discovered that the ocean floor was in fact a complex assortment of peaks and troughs.

In particular, her profiles revealed stark rift valleys, which supported Wegener’s controversial ideas.

Even then, it took a long time to convince the scientific community that her findings were correct.

Eventually, however, she was proved right, and Marie Tharp took her rightful place as one of history’s finest cartographers.

From National Geographic by Betsy Matson

Marie Tharp’s incredible maps were integral to the acceptance of the plate-tectonic theory.

She is one of the most underappreciated scientists in the history of the earth sciences.
Though Marie Tharp was a geologist whose work contributed to the ultimate acceptance and success of the plate-tectonic theory, her legacy has garnered little recognition—and most of it has been for her cartographic endeavors.
In my opinion, however, even the admiration she has received for her maps—including the “Atlantic Ocean Floor” map, published in 1968 in National Geographic magazine (included below)—doesn’t rise to the level that those incredible maps deserve.
The animated short above—created by the Royal Institution and selected by National Geographic’s editors for the Short Film Showcase—gives a nice overview of how Tharp’s work advanced the geological sciences by promoting the acceptance of continental drift and seafloor spreading, the key components of plate tectonics.

 The Mid-Atlantic Ridge stands out in glorious detail on this map of the Atlantic Ocean Floor by Bruce Heezen and Marie Tharp, published as a supplement to the June 1968 issue of National Geographic Magazine.
see "World ocean floor" map

The magnitude of her accomplishment, particularly as a woman in the mid-20th century, working in a field dominated by men, is perhaps best conveyed by Tharp’s own words.

 Through mapping the geology of the ocean floor scientists discovered the mid-Atlantic ridge, a feature that suggested that Wegener's unfashionable theory of continental drift might be correct.

These are her thoughts from a biographical piece she wrote upon winning the Woods Hole Oceanographic Institution’s Mary Sears Woman Pioneer in Oceanography Award in 1999:
“Not too many people can say this about their lives: The whole world was spread out before me (or at least, the 70 percent of it covered by oceans). 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. The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen.”

Links :

• GeoGarage blog : If the ocean was transparent : the see-through sea / The floor of the ocean comes into better focus / The great challenge of mapping the sea / Secretly mapping the sea floor / Marie Tharp: the woman who mapped the ocean floor
• GIS Lounge : Marie Tharp and Mapping the Ocean Floor
• BBC : Wegener’s theory 
• Berkeley : Plate Tectonics: The Rocky History of an Idea