PL ANSWER How is the nature of the geologic activity that is observed near a plate boundary related to the type of plate interaction that occurs at that boundary?

When Earth's tectonic plates grind past one another, enormous amounts of energy can be released in the form of earthquakes. Volcanoes are also often found near plate boundaries because molten rock from deep within Earth called magma can travel upward at these intersections between plates.

By 1962, the idea that pieces of the Earth's surface moved around no longer seemed radical. The concepts of continental drift and seafloor spreading had revolutionized geology (see our module The Origins of Plate Tectonic Theory), and scientists excitedly began to revise their interpretations of existing data into a comprehensive theory of plate tectonics. For example, geologists had long recognized that earthquakes are not randomly distributed on the Earth (see Figure 1).