Geologic Mapping and the Physical Properties of the Ocean

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The endeavor to map the ocean floor

Introduction

Over 70% of the earth's surface is made up of oceans yet these vast expenses are largely unexplored and its bottom left mostly unseen by humans. Today much of what we know about the ocean floor comes from the maps created by one woman, Marie Tharp. Despite her work being completed decades ago we still rely on the maps she created to peer through the ocean waves and to its depths and prove the theory of plate tectonics.

Mapping the Void

Until Marie Tharp and her partner Bruce Heezen began their work in the 1950’s the scientific community largely agreed that the ocean floor was a predominantly flat plain of mud with few important physical or geographical features (beyond the occasional ship or plane wreck of course). So at the time the ocean floor was largely an unexplored blank canvas, one which Marie Tharp would spend the better part of 30 years painting upon. 

At first the project would revolve around the Atlantic ocean as they mapped the floor between Europe and North America, leading to a rather interesting “discovery” (the feature had been found multiple times previously but never really received much attention) a massive ridge line splitting the Atlantic Ocean in two. This mid ocean ridge would be found repeatedly during Tharps work and would be drawn with immaculate detail and would later serve a pivotal role in proving the theory of plate tectonics. In order to map the ocean floor, sonar soundings were used, at the time however, women were not allowed to work aboard ocean vessels and as such Tharp would rely on Heezen to go out and compile the raw data before she sat down with pencils, pens and rulers and began creating the map. She used what is known as the Physiographic mapping technique where one uses lighting/shading and texture to create images rather than directly using color.

As seen in their work Marie and Bruce found not only that the ocean floor was more than a flat muddy plain but a diverse and dynamic environment like the rest of the earth's surface. They found not only sweeping plains and the occasional mountains but also large canyons, trenches, dead and living volcanoes, massive ridges and many more of the features one would commonly attribute to the surface of the earth’s continents. The maps created during this project proved that the ocean floor was just as interesting as the land above and far more complex than what was originally assumed. Among the most notable of these physical features of the ocean was the mid Atlantic ridge which during the process of drawing out the ocean floor she noticed a continuous crack along the length of the ridge line. This along with the fact that the ridge quite literally split the ocean between the americas, africa and europe she emphasized the idea that this could be sea floor spreading and though an unpopular and outright disregarded idea for a time, her observations would slowly become accepted as the mechanism for proving the theory of continental drift and plate tectonics, something that would be even more heavily emphasized when she completed her work and found 10s of thousands of kilometers of ocean ridge lines pushing the crust apart across the world. 

Conclusion

Without the extensive work done by Marie Tharp and her partner Bruce Heezen, much of the ocean floors' physical properties and geography could have gone un-document for years and we likely would never have received maps of this level of detail and quality. In addition without their work the theory of plate tectonics would not have been pushed and the world would have continued on without knowing about the inner workings of the earth, the seafloor and her continents.