22.4 Plate Tectonics

Sometimes a single idea can revolutionize an entire field of study. Many observations that previously made little sense will suddenly fit together. Plate tectonics is such an idea. The discovery of plate tectonics revolutionized the field of geology. Plate tectonics (tek TAHN iks) is the theory that pieces of Earth's lithosphere, called plates, move about slowly on top of the asthenosphere. The theory of plate tectonics explains the formation and movement of Earth's plates.

As recently as the 1960s, many aspects of geology were not well understood. Geologists could not explain why there were mountains in some places and oceans in others. Nor could they explain how fossils of ocean creatures could be found on top of some of the highest mountains. Plate tectonics helps geologists to answer these questions. As you will learn later in this chapter, plate tectonics also does much to explain patterns in the locations of earthquakes and volcanoes.

Figure 22 The Red Sea between Africa and the Arabian peninsula in Asia marks a region where two pieces of the lithosphere are slowly moving apart. Over the next 100 million years, the Red Sea could become an ocean.

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