ch07_prenticehall_plate_tectonics

ch07_prenticehall_plate_tectonics - Continental Drift: An...

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Box 7.1 Understanding Earth: The Breakup of a Supercontinent Box 7.2 Understanding Earth: Susan DeBari—A Career in Geology Box 7.3 Understanding Earth: Plate Tectonics into the Future Composite satellite image of Europe, North Africa, and the Arabian Penisula. (Image © by Worldsat International, Inc., 2001. www.worldsat.ca. All Rights Reserved.) Continental Drift: An Idea Before Its Time The Great Debate: Rejecting an Hypothesis Plate Tectonics: The New Paradigm Divergent Plate Boundaries Convergent Plate Boundaries Transform Fault Boundaries Testing the Plate Tectonics Model Measuring Plate Motion The Driving Mechanism
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CHAPTER 7 Plate Tectonics 191
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192 Unit Three Forces Within W ill California eventually slide into the ocean as some predict? Have conti- nents really drifted apart over the centuries? Answers to these ques- tions and many others that have in- trigued geologists for decades are now being provided by an exciting theory on large-scale movements taking place within Earth. This theory, called plate tectonics, represents the real frontier of the Earth sciences, and its implications are so far-reaching that it can be consid- ered the framework from which most other geological processes should be viewed. Early in this century, most geologists thought that the geographic positions of the ocean basins and conti- nents were fixed. During the last few decades, how- ever, vast amounts of new data have dramatically changed our understanding of the nature and workings of our planet. Earth scientists now realize that the con- tinents gradually migrate across the globe. Where land- masses split apart, new ocean basins are created between the diverging blocks. Meanwhile, older por- tions of the seafloor are carried back into the mantle in regions where trenches occur in the deep-ocean floor. Because of these movements, blocks of continental ma- terial eventually collide and form Earth’s great moun- tain ranges (Figure 7.1). In short, a revolutionary new model of Earth’s tectonic* processes has emerged. This profound reversal of scientific understanding has been appropriately described as a scientific revolu- tion. Like other scientific revolutions, considerable time elapsed between the idea’s inception and its general ac- ceptance. The revolution began early in the twentieth century as a relatively straightforward proposal that the continents drift about the face of Earth. After many years of heated debate, the idea of drifting continents was re- jected by the vast majority of Earth scientists. However, during the 1950s and 1960s, new evidence rekindled in- terest in this proposal. By 1968, these new developments led to the unfolding of a far more encompassing theory than continental drift—a theory known as plate tectonics.
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ch07_prenticehall_plate_tectonics - Continental Drift: An...

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