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12.2 What is the evidence that plates are rigid?
- Plate tectonics theory states that lithospheric plates are rigid, concentrating deformation at their boundaries with little occurring in the interiors.
- Most earthquakes and volcanoes concentrate in narrow zones along plate boundaries, so deformation is restricted to the margins of plates. Intraplate earthquake bands, though, imply a semirigid behavior for some plates.
- Plate tectonics does not explain hot spot volcanoes, but they are few enough not to discount the theory.
- Young, still-growing mountain belts coincide with deforming plate boundaries. Ancient mountain belts mark the location of former plate boundaries.