In the theory of plate tectonics, a boundary between two or more plates. The plates can be moving toward each other (at convergent plate boundaries), away from each other (at divergent plate boundaries), or past each other (at transform faults). Maps of seismic and volcanic activity across the Earth indicate that most earthquakes and volcanic eruptions occur along or near tectonic boundaries. This is because earthquakes and volcanic eruptions are caused by the scraping, pushing, pulling, and melting of the Earth's lithosphere along these boundaries.
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