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Chapter 4: Plate Tectonics

Created by: CK-12


Is the theory of plate tectonics an example of how a theory comes to be?

Scientific ideas do not come to a scientist fully formed. They usually start as observations. Somewhere along the way the scientist develops a hypothesis. The scientist finds evidence to support or refute the hypothesis. If the evidence is in support, the idea evolves into something bigger. By the time an idea is a theory it is extremely complex. A theory has a tremendous amount of data to support it. Nothing substantial refutes it. It probably is extremely important in the area it addresses. Plate tectonics provides a tremendous example of how a theory comes to be. In this section we will follow the development of the theory of plate tectonics. It begins as an observation on how South America and Africa fit together. And becomes the framework on which much of geology hangs.

Chapter Outline

Chapter Summary


In the early 20th century, Alfred Wegener noticed that Africa and South America fit together like puzzle pieces. He was not the first person to make this observation. But he was the first to pursue it. Wegener gathered a tremendous amount of evidence to suggest that the continents had once been joined. He proposed the hypothesis that continents move around on Earth’s surface. He called his hypothesis continental drift. Unfortunately, Wegener could not come up with a plausible mechanism that explained how solid continents could plow through ocean basins. At least not one other scientists would accept. Wegener’s idea was brought back after World War II. Scientists started to put together data about the seafloor. It was not flat, but had astonishing features! There was a the strange pattern of rock ages across the seafloor. Scientists also noticed a strange history of the magnetic north pole on land. In the early 1960s, Harold Hess propose seafloor spreading as a mechanism for drifting continents. The theory of plate tectonics is a combination of continental drift and seafloor spreading. The theory explains what happens as plates of Earth’s lithosphere move around on Earth's surface.

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6 , 7 , 8

Date Created:

Jan 04, 2013

Last Modified:

Feb 26, 2014
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