By RACHEL EVANS
Imagine dropping a rope with a cannon ball tied to the end of it into the ocean to measure depth. Or dropping dynamite into the ocean and waiting for it to hit the bottom and explode. Then imagine using that information to calculate the depth of the ocean.
A magnificent collection of maps created from research done in just this way was donated to the Library's Geography and Map Division (G&M) in 1995 by geologist/cartographer Marie Tharp, who drew the maps from information collected by Bruce Heezen, a marine geologist. Tharp and Heezen's work constituted the first comprehensive mapping of the ocean floor.
Tharp is now assisting G&M as Library staff sort through the collection of more than 40,000 items ranging from water data and geologic and earthquake information, to gravity data, reference maps, technical journals, reports, physiographic diagrams and Heezen and Tharp's ocean floor maps for all of the world's oceans.
In 1947, Tharp and Heezen began working together at Columbia University's Lamont-Doherty Geological Laboratory to systematically define the earth's submarine topography, an immense task. Before they began their research, knowledge of the ocean floor was limited mainly to the harbors and shallow coastal areas necessary for the safe navigation of surface ships. Heezen researched and recorded ocean floor data aboard the Vema, the Lamont ship, while Tharp drew the maps. The physiographic diagrams that Tharp constructed from Heezen's research represented the first comprehensive study of ocean floor topography and greatly expanded public awareness and understanding of ocean floor relief.
In 1959, Tharp and Heezen completed their first map of the North Atlantic; in 1961, they covered the South Atlantic; and in 1964, the Indian Ocean. Heezen completed 33 cruises on the Vema without Tharp on board, because women were not allowed on the ship at the time. After 1965, when Tharp accompanied Heezen for the first time on Vema 34, they revised the map of the Atlantic Ocean twice—in 1968 and 1972. "The data increased because the technology increased," said Tharp.
Tharp remembers drafting maps many times over because of the numerous times the scale changed. First, she drafted in fathoms, then in corrected fathoms, and finally, in the metric system. When asked if she ever felt as if giving up would be easier, Tharp said, "discovering things all the time was part of the fun. It was the era of discovery."
Curiosity is what drove Tharp to a career as a cartographer. She received her first degree in English at Ohio University and, after seeing an advertisement for women to study geology, she headed for the University of Michigan. With her degree in geology, she started working for an oil company in Oklahoma. She knew this wasn't for her and decided to go to night school to earn a degree in mathematics. She then moved on to Columbia University and became involved with a group at the Lamont-Doherty Earth Observatory, where she met Heezen.
Before their work on ocean maps, Heezen and Tharp worked with data from deep sea cameras to help find downed airplanes during World War II. They discovered deep valleys along the ocean floor where U. S. submarines could hide from the enemy. They also discovered where and how transatlantic cables were being broken.
In addition, Tharp confirmed the existence of a north-south mountain ridge that flanked a continuous valley running down the center of the Atlantic. She used the location of earthquakes to help her discover the Mid-Atlantic Ridge, which plate tectonic theory later showed to be a boundary between the North American and European plates. "Earthquakes helped more than anything to map the ocean," said Tharp. Her work with Heezen contributed greatly to the evolution of plate tectonics theory.
After Heezen died in 1973, Tharp wanted "nothing else but to finish the map [we] started." The map of the World Ocean Floor by Tharp and Heezen was copyrighted and printed a year later, and is widely used today.
"It is absolutely remarkable to compare what they did with what can be seen today," says Gary North, the curator of the Heezen-Tharp Collection at the Library. "They were right on."
North retired from the U.S. Geological Survey as the director of the National Mapping Program in 1995. He has been on contract with the Library ever since. North is in the process of sorting through the massive collection of Tharp and Heezen's work. "I am lucky to have a man with his mind and patience to help sort these out," Tharp said.
When North can't identify a piece, he calls upon the expert—Tharp—to help him. "Her memory is unbelievable," said North. According to North, Tharp can identify a piece with very few coordinates, and sometimes only from contour lines, solely from her astonishing memory. "She has the knowledge; she doesn't give herself enough credit," said North.
Tharp and Heezen received the National Geographic Society Hubbard Award in 1978. Tharp herself received an outstanding achievement award from the Society of Women Geographers in 1996, and the Library's Phillips Society honored her as one the 20th Century's Outstanding Cartographers in 1997. She went on to receive the Woods Hole Oceanographic Institution's Women's Pioneer in Oceanography Award in 1999, and the first Lamont-Doherty Honors Award by Columbia University in 2001.
Rachel Evans was an intern in the Public Affairs Office.