Marie
Tharp
1920-2006
Mapped the ocean
floor and advanced
the theory of
continental drift
Painstakingly charted sonar
data of the ocean floor
helped geologists Marie
Tharp and Bruce Heezen
prove the then fringe
theory of plate tectonics.
JOE COVELLOWorld War II gave Marie
Tharp the chance to
make an earthshaking
discovery. Male stu-
dents were off fighting,
and universities had
desks to fill. Tharp, who
already had degrees
in English and music,
seized the opportunity
to study geology,
a field that had been
hostile to women. After
a stint as a field geol-
ogist for an oil com-
pany, she was hired as
a technical assistant at
Columbia University’s
Lamont Geological
Observatory, where she
met a graduate student
named Bruce Heezen.
Together Tharp and
Heezen embarked on
a bold project: to map
the ocean floor.
Women were barred
from working aboard
scientific research ships
then, so Heezen used
sonar measurements
he collected on ocean
expeditions, including
some funded by
National Geographic.
In a basement office at
Columbia, Tharp trans-
formed the data and
measurements from
hundreds of other
expeditions into maps.
As Tharp worked on
the first map of the
Atlantic Ocean, she
noticed a valley running
across the ocean floor
and concluded that
pieces of the Earth’s
crust were shifting. Her
theory of continental
drift was “almost a form
of scientific heresy,”
Tharp would say later.
At first Heezen didn’t
accept her theory,
mocking her evidence
as “girl talk.” But her
conclusion was bol-
stered by sonar read-
ings. This crack in the
Earth convinced the
scientific community
that the continents had
been one landmass,
later separated by
tectonic movement.
Backed by the
U.S. Navy and NationalGeographic, the proj-
ect spread from Colum-
bia to Tharp’s home in
South Nyack, New York.
It was published in 1977
as the “World Ocean
Floor” map, the first
global depiction of the
bottom of the oceans.
It revealed a landscape
covered in volcanic
ranges and Everest-
high peaks, split by
a 40,390-mile seam
running along the
Earth’s surface.
“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,”
she wrote.
The year after the
map was published,
Tharp and Heezen won
the Hubbard Medal,
National Geograph-
ic’s highest honor,
which recognizes life-
time achievement in
research, discovery,
and exploration.
Tharp opened a map-
distribution business
after she retired from
Columbia. By then,
she finally had made it
aboard a research ves-
sel. She died in 2006.128 NATIONAL GEOGRAPHIC