Page 15 - NYS_ESS_03-2024

One of her important innovations a talk at Princeton in 1957 and showed Geographic in 1967, and a 1977
was creating sketches depicting what the rift valley and epicenters, geology World Ocean Floor map that is now
the seafloor would look like. These department chair Harry Hess replied, held at the Library of Congress.
views made it easier to visualize the “You have shaken the foundations After Heezen died in 1977, Tharp
ocean floor’s topography and create a of geology.” continued her work until her death
physiographic map.
Tectonic resistance in 2006. In October 1978, Heezen
Tharp’s careful plotting of six east-to-west In 1959 the Geological Society of America (posthumously) and Tharp were awarded
profiles across the North Atlantic revealed published “The Floors of the Oceans: I. the Hubbard Medal, the National
something no one had ever described The North Atlantic” by Heezen, Tharp Geographic Society’s highest honor,
before: a cleft in the center of the ocean, and “Doc” Ewing, director of the Lamont joining the ranks of explorers and
miles wide and hundreds of feet deep. Observatory, where they worked. It discoverers such as Ernest Shackleton,
Tharp suggested that it was a rift valley – contained Tharp’s ocean profiles, ideas and Louis and Mary Leakey and Jane Goodall.
a type of long trough that was known to access to Tharp’s physiographic maps.
exist on land. Today ships use a method called swath
Some scientists thought the work was mapping, which measures depth over
Heezen called this idea “girl talk” and told
Tharp to recalculate and redraft. When brilliant, but most didn’t believe it. French a ribbon-like path rather than along
she did, the rift valley was still there. undersea explorer Jacques Cousteau was a single line. The ribbons can be
determined to prove Tharp wrong. Sailing stitched together to create an accurate
Another research assistant was plotting aboard his research vessel, the Calypso, he seafloor map.
locations of earthquake epicenters on a purposely crossed the mid-Atlantic Ridge
map of the same size and scale. Comparing and lowered an underwater movie camera. But because ships move slowly, it would
the two maps, Heezen and Tharp realized To Cousteau’s surprise, the film showed take one ship 200 years to completely
that the earthquake epicenters fell inside that a rift valley existed. map the seafloor. An international effort
the rift valley. This discovery was critical to to map the entire ocean floor in detail
the development of plate tectonic theory: “There’s truth to the old cliché that a by 2030 is under way, using multiple
It suggested that movement was occurring picture is worth a thousand words and ships, led by the Nippon Foundation
in the rift valley, and that the continents that seeing is believing,” Tharp observed and the General Bathymetric Chart of
might actually be drifting apart. in a 1999 retrospective essay. the Oceans.

This insight was revolutionary. When What could have created the rift? This information is critical to beginning
Heezen, as a newly-minted Ph.D., gave Princeton’s Hess proposed some ideas to understand what the seafloor looks
in a 1962 paper. It postulated that hot like on a neighborhood scale. Marie
magma rose from inside the Earth at the Tharp was the first person to show the
rift, expanded as it cooled and pushed two rich topography of the ocean floor and its
adjoining plates further apart. This idea different neighborhoods.
was a key contribution to plate tectonic Suzanne O’Connell is a Professor
theory, but Hess failed to reference the of Earth & Environmental
critical work presented in “The Floors of Sciences at Wesleyan University.
the Oceans” – one of the few publications Article and photos published
that included Tharp as a co-author. in The Conversation
“Academic rigor, journalist
Still surveying flair” at theconversation.com.
Tharp continued working with Heezen Opening photo credit: Lamont-Doherty Earth
to bring the ocean floor to life. Their Observatory and the estate of Marie Tharp
collaboration included an Indian
Ocean map, published by National

An illustration of Marie Tharp’s mapping process.
(a) shows the position of two ship tracks (A,
B) moving across the surface. (b) plots depth
recordings as profiles, exaggerating their height
to make features easier to visualize. (c) sketches Marie Tharp in July 2001. Left. Detail of Canary Islands from Marie Tharp’s physiographic map of the
features shown on the profiles. The Floors of the Bruce Gilbert, Lamont- North Atlantic. Right. Modern swath mapping depiction of the same area.
Ocean, 1959, Fig. 1 Doherty Earth Observatory Colors indicate depth. Vicki Ferrini, Lamont-Doherty Earth Observatory.
EMPIRE STATE SURVEYOR / VOL. 60 • NO 2 2024 • MARCH/APRIL 13