Marie Tharp's groundbreaking maps brought the seafloor to the world

Marie Tharp’s groundbreaking maps introduced the seafloor to the world


Stroll the halls of an instructional earth sciences division, and also you’ll possible discover displayed on a wall someplace a strikingly stunning map of the world’s ocean flooring. Accomplished in 1977, the map represents the fruits of the unlikely, and underappreciated, profession of Marie Tharp. Her three many years of labor as a geologist and cartographer at Columbia College gave scientists and the general public alike their first glimpse of what the seafloor seems like.

In the midst of the 20th century, when many American scientists have been in revolt in opposition to continental drift — the controversial concept that the continents will not be mounted in place — Tharp’s groundbreaking maps helped tilt the scientific view towards acceptance and clear a path for the rising idea of plate tectonics.

Tharp was the precise particular person in the precise place on the proper time to make the primary detailed maps of the seafloor. Particularly, she was the precise lady. Her gender meant sure skilled avenues have been primarily off-limits. However she was capable of make the most of doorways cracked open by historic circumstances, turning into uniquely certified to make vital contributions to each science and cartography. With out her, the maps might by no means have come to be.

“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,” Tharp recalled in a 1999 perspective. “The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen.”

map of the world
With funding from the U.S. Navy, Marie Tharp and Bruce Heezen produced this 1977 map with Austrian painter Heinrich Berann. It has turn into iconic amongst cartographers and earth scientists.Library of Congress, Geography and Map Division

Tharp’s cartographic roots ran deep. She was born in Michigan in 1920 and as a younger woman would accompany her father on subject journeys to survey land and make maps for the U.S. Division of Agriculture’s Bureau of Soils, a job that stored the household on the transfer. “By the time I finished high school I had attended nearly two dozen schools and I had seen a lot of different landscapes,” Tharp recalled. “I guess I had map-making in my blood, though I hadn’t planned to follow in my father’s footsteps.”

Tharp was a pupil on the College of Ohio in 1941 when the assault on Pearl Harbor emptied campuses of younger males, who have been becoming a member of the army in droves. This sudden shortage of male college students prompted the College of Michigan’s geology division to open its doorways to girls. Tharp had taken a few geology courses and jumped on the alternative. “There were 10 or 12 of us that appeared from all over the United States, girls. With a sense of adventure,” she recalled in an oral historical past interview in 1994. Tharp earned a grasp’s diploma in 1943, finishing a summer time subject course in geologic mapping and dealing as a part-time draftsperson for the U.S. Geological Survey alongside the way in which. Upon graduating she took a job with an oil firm in Oklahoma however was bored by work that concerned neither fieldwork nor analysis. So she enrolled in evening courses to earn a second grasp’s diploma in arithmetic from the College of Tulsa. 

In search of extra pleasure, she moved to New York Metropolis in 1948. When she walked into the Columbia College geology division on the lookout for a job, her superior levels bought her an interview, however the one place accessible to a lady was that of a draftsperson helping male graduate college students working towards a level in geology that she had already earned. Nonetheless, it appeared extra promising than the opposite job she had inquired about — learning fossils on the American Museum of Pure Historical past — so she took it.

The next 12 months Tharp turned one of many first girls employed by Columbia’s newly based Lamont Geological Observatory and shortly was working solely with geologist Bruce Heezen, a newly minted Ph.D. Like most of the male scientists at Lamont, Heezen was primarily occupied with gathering ocean information, which Tharp would then analyze, plot and map — work she was greater than certified to do. 

“These men considered it glamorous and pleasurable to go to sea, far more so than staying at home to analyze [the data],” writes science historian Naomi Oreskes of Harvard College in her forthcoming ebook Science on a Mission: How Navy Funding Formed What We Do and Don’t Know Concerning the Ocean. “This is one reason data analysis was often left to women.” Actually, girls usually weren’t allowed on the analysis ships in any respect.

black and white graphs of data
To generate the seafloor maps, Marie Tharp began with two-dimensional ocean profiles (prime) after which used her intensive geologic data to decipher landforms and fill within the clean areas (backside).B.C. Heezen, M. Tharp, and M. Ewing/Lamont-Doherty Earth Observatory/Geological Society of America Particular Paper 1965

Barred from ocean expeditions, Tharp poured all of her power into mapping the seafloor beginning with the North Atlantic, work that may result in two necessary discoveries. To make a map, she first translated the echo soundings gathered by ships crossing the ocean into depths after which created two-dimensional vertical slices of the terrain beneath the ships’ tracks. These ocean-floor profiles confirmed a broad ridge operating down the center of the Atlantic. Although the characteristic had been roughly mapped within the 19th century, Tharp seen a notch close to the highest of the ridge in every of the profiles. She believed the notches represented a steady, deep valley operating down the middle of the mid-ocean ridge. If she was proper, the valley is likely to be a rift the place molten materials got here up from beneath, forming new crust and pushing the ocean flooring aside — proof that might assist continental drift.

The concept the continents weren’t mounted in place had gained traction in Europe, however Heezen, like most U.S. scientists on the time, “considered it to be almost a form of scientific heresy,” Tharp later wrote in Pure Historical past journal. It took her a 12 months or so to persuade Heezen that the rift was actual, and it took the 2 a number of extra years to complete their first map of the North Atlantic in 1957.

With a view to publish that first map and share their work with different scientists, Tharp and Heezen needed to get across the U.S. Navy’s Chilly Battle–impressed choice to categorise detailed topographic maps that used contour strains to point depths. This was one of many causes the pair selected to adapt a comparatively new cartographic type generally known as a physiographic diagram, a type of three-dimensional sketch of terrain as if seen from an airplane window. To do that, Tharp had to make use of her coaching as a geologist and expertise with mapping on land — data and expertise {that a} typical analysis assistant or draftsperson wouldn’t have had.

Physiographic maps had beforehand been used to signify continental landforms with standardized symbols. Every kind of mountain, valley, plain and desert was sketched in a particular means. Tharp and Heezen have been the primary to make use of the method to point out what unknown, unseeable terrain would possibly appear to be. Tharp first sketched a strip of seafloor alongside every profile, deciphering what kind of landform every bump and dip was prone to be. Then she recognized patterns to fill within the clean areas between the profiles.

detailed map of landforms
Bruce Heezen and Marie Tharp’s physiographic maps, this one of many North Atlantic first printed in 1957 and once more in 1959, gave scientists a compelling visible comparability to continental landforms they understood.Physiographic Diagram of the North Atlantic Ocean (1959) by Heezen and Tharp; reproduced by permission of Marie Tharp Maps LLC and the Lamont-Doherty Earth Observatory

“The amount of work involved in taking it from just from those soundings and being able to create that is just amazing,” says historian Judith Tyner, writer of Girls in American Cartography.

As Tharp was creating her map, an unrelated venture was taking form on the drafting desk subsequent to hers. Heezen had employed a latest artwork faculty graduate to plot hundreds of earthquake epicenters within the Atlantic Ocean to assist Bell Labs discover the most secure locations to put transoceanic cables. The epicenters he was plotting lined up with Tharp’s rift valley. The correlation lent weight to the concept that the rift was the place the crust was pulling aside, and gave Tharp a strategy to precisely find the rift between the ship tracks.

Heezen and Tharp’s 1957 diagram of the north Atlantic Ocean was by far essentially the most exhaustive seafloor map ever produced.

“The marvelous thing about that map is how comprehensive it looked on rather limited data,” says science historian Ronald Doel of Florida State College in Tallahassee. “But the earthquake data also helped to make clear just where the ridges are oriented and where the associated geological features are.”

The American scientific neighborhood was initially skeptical, cautious of the speculative nature of their map. However because the pair continued mapping the remainder of the Atlantic and moved on to different oceans, proof amassed for a steady ridge, with a rift valley at its heart, stretching for some 60,000 kilometers throughout the globe. 

Tharp and Heezen’s modern use of the physiographic technique gave scientists a compelling visible comparability to continental landforms they understood. This helped persuade them that simply because the East African Rift was splitting that continent, the submarine rift valley marked the place the continents on both facet of the Atlantic had pulled away from one another.

“That’s why her map is so powerful,” says historian of geology David Spanagel of Worcester Polytechnic Institute in Worcester, Mass. “It allows people to see the bottom of the ocean as if it were a piece of land, and then reason about it. That’s a transformative thing that she’s able to accomplish.”

Nationwide Geographic additionally took discover of the maps and invited Heezen and Tharp to collaborate on some ocean illustrations with the Austrian painter Heinrich Berann, who would turn into well-known for his mountain panoramas. The beautiful ocean-floor depictions have been included as poster-sized dietary supplements in problems with Nationwide Geographic journal between 1967 and 1971. The journal had a circulation of 6 million or 7 million on the time, giving a large swathe of the general public a window into the ocean.

In 1973, Heezen and Tharp obtained a grant from the U.S. Navy to work with Berann on a whole map of the world’s ocean flooring. It took the trio 4 years to create their iconic cartographic masterpiece, an unparalleled, panoramic visualization that continues to form how each scientists and the general public take into consideration the seafloor.

The map was completed simply weeks earlier than Heezen died of a coronary heart assault at age 53, whereas in a submarine exploring the mid-ocean ridge close to Iceland. His demise left Tharp with out a supply of funding and information, primarily ending her exceptional profession. It might be many years earlier than her contributions have been absolutely acknowledged. However not like many different unsung figures within the historical past of science, the accolades started rolling in earlier than she died of most cancers in 2006. Over the past decade of her life, Tharp obtained prestigious awards from a number of establishments together with Lamont — now generally known as the Lamont-Doherty Earth Observatory — and the Library of Congress, which named her one of many 4 best cartographers of the 20th century.

“Can you imagine what heights she would have risen to in her profession,” says Tyner, “if she’d been a man?”

Although hers was at all times the second title, after Heezen’s, on the maps they made, and doesn’t seem in any respect on most of the papers her work contributed to, Tharp by no means expressed any regrets about her path. “I thought I was lucky to have a job that was so interesting,” she recalled in 1999. “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.”



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