Marie Tharp's Seafloor
A Story Map for Marie Tharp's 100th birthday
Marie Tharp began working at Columbia University in 1948, where she was a member of Maurice Ewing’s geophysics team. In 1952 she began working with Bruce Heezen at the recently established Lamont-Doherty Geological Observatory. She was given a large dataset of echo-sounding data - profiles of depth to the seafloor collected by research vessels traversing the oceans. The data were presented on rolls of paper, tens of meters long, and Marie was given the task of figuring out how to represent these data meaningfully.
Marie Tharp photograph, courtesy of Lamont-Doherty Earth Observatory and the estate of Marie Tharp.
Marie initially focused her efforts on data from the North Atlantic, as part of a project funded by Bell Laboratories to understand what was causing repeat damage to underwater communication cables. At the time, the best representations of seafloor depth were contour charts with spot soundings made available by the General Bathymetric Chart of the Ocean (GEBCO).
Several expeditions aboard the Lamont research vessel Vema from 1953 - 1957 provided echo sounding data along sparse transects across the Atlantic Ocean.
The R/V Vema was operated by the Lamont-Doherty Geological Observatory from 1953 to 1981.
Learn more about the Vema in this Map Journal .
Data acquired aboard the Woods Hole Oceanographic Institution (WHOI) research vessel Atlantis from 1946 - 1953 were shared with Marie as she began to assemble the first detailed map of the Atlantic Ocean.
The original R/V Atlantis was operated by Woods Hole Oceanographic Institution from 1930 - 1964.
Marie began to piece the data together like a giant puzzle. From the paper rolls of data and navigational tracks, she created profiles that she aligned and vertically exaggerated to better understand the shape of the seafloor. This revealed the consistent presence of a shallower, mountainous region with a notch at its crest - which she was able to trace throughout the region. She referred to this, in 1952, as a 'Rift'. Eventually, overlaying earthquake epicenters on her map revealed a correlation between earthquakes and the rift.
Marie Tharp's maps excited work in seafloor spreading and were fundamental to the plate tectonics revolution.
Marie built her physiographic map of the Atlantic Ocean by assembling sparse echo-sounder profiles collected aboard multiple expeditions.
She rendered the echo-sounding profiles onto a map based on the navigation of the vessel.
For each transect, she stylized the profiles to portray her interpretation of the seafloor.
She then filled the gaps between transects by extending her stylized views based on a combination of data and her knowledge and understanding of geology.
In 1959, Marie Tharp and Bruce Heezen published the Physiographic Diagram of the North Atlantic Ocean.
This map not only presents the stylized echo-sounding data, but also includes textural information based on observations of sediment thickness.
The use of vertical exaggeration and depiction of this information as a physiographic diagram revealed, for the first time, the fabric of the seafloor.
The Mid-Atlantic Ridge and its rift valley are clearly evident with details that could not have been revealed or understood with traditional contour maps.
One of the most remarkable things about this new map of the Atlantic Ocean is how consistent it is with modern maps of the same area, which are based on orders of magnitude more data than existed when Marie did her work.
Use the slider tool below to explore for yourself. In this tool you can compare the 1959 Tharp and Heezen map with the latest version of the Global Multi-Resolution Topography (GMRT) Synthesis, which is curated today at Lamont with support from the US National Science Foundation.
Interactive maps of the North Atlantic Physiographic Diagram [Heezen and Tharp, 1959] courtesy of Lamont-Doherty Earth Observatory and the estate of Marie Tharp (left), and the current Global Multi-Resolution Topography (GMRT) Synthesis actively curated at Lamont-Doherty Earth Observatory (right).
After completing the map of the North Atlantic, Marie continued her work in the South Atlantic (1961), and then the Indian Ocean (1964).
Her understanding of geology was immense and underutilized.
She began to piece together observed trends related to Fracture Zones - large lateral offsets on the seafloor.
Working with a globe that had plastic see-through skin that could be moved around, she mapped these fracture zones on a sphere.
The power of her intellect was highlighted by her physiographic map of the Indian Ocean which was based on extremely limited data, but identified the trends extraordinarily well.
In addition to Lamont-led expeditions, collaboration with colleagues around the world yielded more data and information for Marie to bring together in her maps of the seafloor.
Marie's map of the Indian Ocean was published as a panorama in National Geographic in 1977.
The famous World Ocean Floor Panorama, painted by Heinrich Berann, was published in 1977. It was based on 25 years of Marie Tharp's work throughout the oceans. Through the use of vertical exaggeration, it is a cartographic masterpiece that delivered detailed information about the shape of the global seafloor in a way that could be easily understood by scientists and the public alike.
Just months before the publication of the World Ocean Floor panorama, Bruce Heezen died during an expedition aboard a submarine south of Iceland. Although Bruce did not live to see the publication of the 1977 World Ocean Floor panorama, Lamont colleague Bill Ryan collaborated with Marie to complete the project. Marie worked at Lamont for several more years, but never fully recovered from the loss of her intellectual partner Bruce Heezen.
Marie Tharp’s work is one of the best early examples of what comes from sharing and integrating data from multiple sources.
Recognizing Marie Tharp's Contributions
Marie was not fully credited for her work - typical treatment for women scientists of that time period. Sometimes deliberately omitted as a co-author on scientific publications, and never listed in the lead author position, her work was nonetheless transformative, not only in the Earth Sciences, but also in the fields of marine cartography and the popularization of science. In the sunset of her life, Marie received several prestigious awards from scientific societies. Interest in her achievements grew tremendously after her passing in 2006.
1978 - National Geographic Society’s Hubbard Medal
1996 - Society of Woman Geographers Outstanding Achievement Award
1997- Library of Congress named her one of the four outstanding cartographers of the 20th Century
1999 - Woods Holes Oceanographic Institution’s Mary Sears Woman Pioneer in Oceanography Award
2001 - Lamont–Doherty Earth Observatory Heritage Award
2015 - International Astronomical Union named a moon crater in her honor.
Her unique skill was figuring out how to understand and portray the shape of the ocean floor.
Marie Tharp's Ongoing Legacy at Lamont
GMRT base map (www.gmrt.org)
As we recognize what would be Marie Tharp's 100th birthday, we have made significant strides in the field of global ocean floor mapping. The Global Multi-Resolution Topography (GMRT) Synthesis is an ongoing effort at LDEO that builds upon Tharp's pioneering work and focuses on integrating multibeam sonar data acquired throughout the global ocean. The GMRT project stemmed from an earlier compilation effort, the Ridge Multibeam Synthesis, which began at Lamont in the early 1990s. GMRT is funded by the National Science Foundation and offers the high-resolution elevation data nested within lower resolution data, and is a global leader in integrating bathymetry data acquired with multibeam sonar data. Initiated by Bill Ryan, Bill Haxby and Suzanne Carbotte in 2002, GMRT has continued to grow under the leadership of Suzanne Carbotte and Vicki Ferrini and in 2020 offered data from more than 1,100 research expeditions covering more than 9% of the global ocean. GMRT is a significant contributor to the Nippon Foundation - GEBCO Seabed 2030 Project which aspires to map the entire ocean by the year 2030. The Seabed 2030 Regional Center for the Atlantic and Indian Oceans is hosted at LDEO and led by Dr. Vicki Ferrini.
Modern efforts to build a global ocean map rely on the contributions of countless individuals, projects and organizations - each providing a piece of the puzzle.
Related Content
AGU Fall Meeting 2018 - U22A: The Giants of Tectonophysics
Marie Tharp's Ongoing Legacy in Global Seabed Mapping Efforts
2020 European Geoscience Union Session on Marie Tharp: Blog Post
About Marie Tharp - resources and information from Lamont-Doherty Earth Observatory
