Plate Tectonics Plate tectonics are a relatively new theory that has revolutionized the way geologists think about the Earth. According to the theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building. Plate tectonics is a combination of two earlier …showed first 75 words of 2452 total…

…showed last 75 words of 2452 total…boundary, lithospheric plates move toward each other. The west margin of the South American continent, where the oceanic Nazca Plate is pushed toward and beneath the continental portion of the South American Plate, is an example of a convergent plate boundary. At a transform plate boundary, plates slide past each other. The San Andreas Fault in California is an example of a transform plate boundary, where the Pacific Plate slides past the North American Plate.