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Abraham Ortelius
Dutch mapmaker Abraham Ortelius proposed that the Americas seemed ripped from Europe and Africa, perhaps from earthquakes and floods. He thought that the continents were once joined together by noticing that the coastlines seemed to fit together. -
Wegener's Hypothesis
German meteorologist Alfred Wegener posed the idea that the continents had once been joined as a supercontinent he named Pangaea. He noticed that the continents fit together like a puzzle and he found fossil, rock, and climate evidence that support his hypothesis. However, Wegener's hypothesis was rejected because he could not give an explanation as to how the continents could have moved. -
Arthur Holmes
Arthur Holmes, a British biologist, tried to give an explanation that the continents could have moved because of thermal convection. The idea that once a substance heats, cools, and moves to the surface a certain amount of times it could cause the land to change and move is called thermal convection. Holmes's proposal was not accepted at the time, but later gained support. -
Technology: Sonar
In the 1950's, the Sonar was used by Maurice Ewing and the Navy to map the ocean floor. This instrument works by sending out sound waves and timing how long it took to return to determine a specific spot's depth. Sonar helped discover underwater mountain chains with a large crack at the top, called mid-ocean ridges. Sonar stands for SOund, NAvigation, and Ranging. -
J. Tuzo Wilson
J. Tuzo Wilson was a Canadian geologist who was influenced by Harry Hess' ideas and inspired by Wegener's hypothesis of a continental drift. He suggested that the Hawaiian and other volcanic island chains formed due to the movement of a plate over a "hotspot" in the mantle. He discovered a new type of plate boundary, known as the transform fault boundary. -
Harry H. Hess and Seafloor Spreading
The American geophysicist Harry H. Hess studied mid-ocean ridges while serving the U.S Navy during World War 2. Using the infomation he had gathered, Hess proposed that molten material breaks through a crack in the center, causing it and the sea floor to spread until it sinks back into the mantle at trenches. The magnetic properties of ocean-floor rock, earthquake patterns, and the age of the ocean floor were all evidence that supported Hess's hypothesis. -
The Glomar Challenger
A drillship named the Glomar Challenger drilled holes into the ocean floor so that rock samples could be retrieved. The samples showed that rocks got older the farther they were from the mid-ocean ridge and that newer crust formed at the center of the ridge.
