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Article: Plate Tectonics
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Plate Tectonics
Plate tectonics is the unifying theory of geology that describes and explains that all earthquakes, volcanic activity, and mountain-building processes are caused by the gradual movement of rigid slabs of rock, called plates, that make up the Earth's surface layer. Given the expanse of geologic time, even modest movements
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measured in centimeters or inches per year
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result in substantial changes in the distribution of lands and oceans over millions of years.
Earth Structure
The Earth's internal structure can be viewed in two ways: either in terms of compositional layers, or in terms of layers of varying strength. There are three main compositional layers: the ...