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Plate Tectonics

A unifying, and relatively recent, theory which encompasses much of the preceding evidence for a dynamic Earth is plate tectonics. In this theory the Earth is believed to be composed of a number of different plates which ``float'' (over a long time scale) over the surface of the Earth. These boundaries of these plates are indicated in the Figure below.

Figure 14.4: Tectonic plates
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As well as explaining continental drift qualitatively, the way that plates can meet provides us with an understanding of many of the changes that occur on the Earth.