I never got to meet Marie Tharp, one of my mapping heroes who died in 2006. She left seventy two boxes filled with maps, letters, photographs and sketches (along with her house!) to the Library of Congress in Washington DC. I recently had a look at some of this material.
The North Atlantic Ocean floor was first mapped in detail by Marie, in partnership with Bruce Heezen, in 1957. Their groundbreaking map revealed canyons, ridges, submarine mountains, valleys and rifts inside what were previously thought to be flat, monotonous ocean basins. The mid-Atlantic Ridge represented a major scientific discovery at that time. It provided important evidence supporting the emerging and controversial theory of plate tectonics.
Perhaps the best known part of Marie’s legacy is the World Ocean Floor Panorama, published by the National Geographic in 1977. This was the culmination of numerous regional ocean floor mapping projects. As Marie wrote in a letter that same year “it summarises in one fairly large piece of paper what we have learned over the past 25 years”. Having delved through some of the track diagrams, sounding plots, sketches and early production drafts of her work, Marie was certainly no stranger to large pieces of paper, or hard work!
One preliminary sketch of the southern Pacific and Indian Oceans stretched across three tables in the Geography and Map reading room of the library (Fig 1). It showed the enormous effort that would have gone into Marie’s maps. She spent many hours plotting by hand the different datasets she had gathered to visualise regional seafloor patterns. Tracks, soundings and contours were then sketched independently, before any work on the actual map started.
Marie plotted measurements collected by research ships and filled in the blanks with educated guesswork. This was informed by other data she laid her hands on, such as earthquake locations along the mid-Atlantic Ridge. The close correspondence between her maps and later satellite-derived images of the seafloor is remarkable, and testifies to the accuracy of her work.
Alongside their scientific contribution, Marie’s maps engaged the public imagination, and continue to have a widespread legacy. This stems s from her collaboration with Austrian artist Heinrich Berann, who painted the World Ocean Floor Panorama (Fig 2). This collaboration brought together two separate disciplinary approaches to representing natural features.
In an era when academic researchers were judged by their technical acumen and output, Marie found the time and energy to work with a painter in remote Austria. This was a big effort. It took numerous trips to visit Heinrich in his remote Austrian studio (Fig 3). I found many pages of notes from Marie to Heinrich outlining basic ideas about data. It was not something that came naturally to many scientists, indeed, a description of how they all worked together revealed that Bruce hovered by the studio door, never quite feeling comfortable among the canvases, oils and renaissance paintings that were piled up against the walls. Was it worth the effort, for a woman who wrote great handfuls of letters, gathering data to make hundreds of maps each year?
One box contained a letter from National Geographic forwarding on pages and pages of praise for the World Ocean Floor Panorama from their readers. The map had galvanized the public imagination, prompting school teachers to tell their classes about the strange and wonderful seafloor, and many readers and nature enthusiasts to turn their attention to this foreign environment, asking where they could find out more about submarine mountains and mid-ocean ridges. The World Ocean Floor panorama still reaches millions of desk-based explorers today as the submarine data layer in Google Earth.
Marie’s interdisciplinary collaboration with Heinrich Berann gave her cartographic work a reach beyond that of many academic journal articles. It may have taken a leap into the unknown, a lot of time and effort and many of her contemporaries may have wondered what the point of it all was. But these maps interested many people in the seafloor, and they were important evidence for historic scientific discovery. Surely that makes it worth the effort.