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textbook from the time “admitted” that “the cause of crustal of years).” For the scientific community it was figurative; Tharp
deformation is one of the great mysteries of science and can be recalled that her first depiction of the ocean floor was called “a
discussed only in a speculative way” (Longwell et al., p. 18). bunch of lies,” and Bill Menard remarked in a letter to Heezen that
Tharp recalled being taught in grad school what continental drift he was “increasingly distressed to read one account after another
was—but not in a way that suggested it was a realistic possibility. in the press and magazines of this fabulous rift valley.”

In one of the few stories she related about her time at Michigan, The first detailed physiographic diagram of the ocean floor was
Tharp recalled a talk and visit from the state geologist. At a post- published by the Geological Society of America in 1957; diagrams
presentation tea, the PG Girls were given the chance to ask him of the other oceans followed in quick succession, each one reveal-
questions. What was it like to be in this field? What would a job in ing a newly discovered feature that helped scientists develop the
the real world be like? Just what, their questions implied, were interlocking hypotheses that together revolutionized Earth history.
they getting themselves into? “And lo and behold what did this With the hope that the public might become as fascinated with
geologist say?” Tharp remembered, “He said the geologist is the inner space as they were with outer space, Tharp and Heezen col-
best one on the spot to make an educated guess.” The geologist’s laborated with National Geographic on a series of accessible
best tool, in other words, was the ability to look at an incomplete artistic renderings of the ocean floors, the first of which appeared
picture and make a hypothesis about what that picture meant. in 1967. By the late 1960s, the plate tectonics revolution was com-
plete; a few years later, grade-schoolers were learning why South
DISCOVERIES AND IMPACT America and Africa looked like they’d fit together if an ocean
wasn’t dividing them. And by 1977, Tharp and Heezen published
Tharp’s unconventional educational history made possible her their World Ocean Floor Panorama, a map that’s still ubiquitous
1952 discovery of the worldwide mid-oceanic rift valley. In addi- in the textbooks and halls of geology departments today.
tion to her eclectic undergraduate coursework, she rounded out
her scientific training while at Michigan, taking extra classes in REFERENCES
physics, math, and chemistry. Before landing a job at Maurice
Ewing’s newly formed geophysical lab at Columbia University in Barton, C., 2002, Marie Tharp, oceanographic cartographer, and her contribu-
1948, she worked for a time at Standard Oil in Tulsa, Oklahoma, tions to the revolution in the earth sciences, in Oldroyd, D., ed., The Earth
USA, during which time she earned a degree in math to combat Inside and Out: Some Major Contributions to Geology in the Twentieth
the boredom of being stuck in an office. Despite her extensive Century: Geological Society, London, Special Publication 192, p. 215–228.
education, she was hired at Lamont to draft and compute—a
research assistant to younger male graduate students. Boredom Felt, H., 2012, Soundings: The Story of the Remarkable Woman Who Mapped the
became a problem for Tharp there, too. Only after she quit did Ocean Floor: New York, Henry Holt & Company, 368 p.
Ewing realize that she needed more stimulating work; he asked
her to come back and assigned her to work with Bruce Heezen. Heezen, B.C., Tharp, M., and Ewing, M., 1959, The Floors of the Oceans I.
The North Atlantic: Geological Society of America Special Paper 65, 126 p.,
Tharp and Heezen began their 25-year-long partnership in 1952 30 plates.
by processing thousands of unexamined sounding records of the
North Atlantic Ocean floor. While Heezen spent much of his time Longwell, C.R., Knopf, A., and Flint, R.F., 1941, Outlines of Physical Geology:
at sea and working on other projects, Tharp used the sounding New York, John Wiley and Sons, 313 p.
records to compile six profiles that stretched across the North
Atlantic; even if she had wanted to go to sea, women at that time Tharp, M., 1999, Connect the dots: Mapping the seafloor and discovering the
were not permitted on Lamont’s or most ships. The northernmost mid-ocean ridge, in Lamont-Doherty Earth Observatory of Columbia
profile began at Martha’s Vineyard, the southernmost one at University: Twelve Perspectives on the First Fifty Years 1949–1999,
Recife, Brazil. But the picture was incomplete. What was happen- p. 31–37, http://www.whoi.edu/sbl/liteSite.do?litesiteid=9092&articleId
ing in the hundreds of miles separating each profile? To fill in the =13407 (last accessed 2 Feb. 2016).
blanks, Tharp used temperature readings, salinity measurements,
and cores to reveal, for the first time, a rift valley trending down Marie Tharp and her globe of the seafloor. Image courtesy Lamont-Doherty
the center of the Mid-Atlantic Ridge. The (American) scientific Earth Observatory.
establishment was still hostile to any implication that Wegener’s
continent drift hypothesis might be true—and the rift valley was a
10,000-mile-long piece of evidence. Afraid of possible repercus-
sions, Heezen called Tharp’s work “girl talk” the first time he saw
it. Only after she re-drew the profiles twice and showed him that
the valley’s pattern correlated with newly mapped earthquake
epicenters in the North Atlantic did he accept the valley’s exis-
tence—a correlation that also allowed Tharp to extend the rift
valley out of the Atlantic and across the entire world.

The discovery of a 40,000-mile-long, worldwide mid-oceanic
rift valley shocked scientists and the public, both groups worrying
that their worlds might be shattered. For the public it was quite
literal; in a letter to one concerned woman, Heezen wrote, “I do
not believe that you have any immediate worry. The earth seems
to have been ‘ripping at the seams’ for a long time now (millions

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