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9-5 The Theory of Plate Tectonics 1. 2. Discuss the theory of plate tectonics? Describe the three types of plate boundaries? Plate Tectonics Geological theory that states that pieces of the Earth’s Lithosphere are in constant, slow motion, driven by convection currents in the mantle. The Theory of Plate tectonics explains the formation, movement, and subduction of Earth’s plates. J. Tuzo Wilson 1965 proposed that the lithosphere was broken into pieces creating sections called plates Stated that the plates closely fit together along cracks in the lithosphere Plate Tectonics video Characteristics of Plate Tectonic As plates move they collide, pull apart, and grind past each other Convection currents in the asthenosphere provide the energy for movement. Plated move away from each other at rifts or ridges and toward each other at convergent zones. Plate boundaries three types Convergent – plates coming together Divergent – plates moving apart Transform- plates sliding past each other Transform Boundaries Two plates sliding past each other Frequent Earthquakes San Andreas Fault California Divergent Boundaries Plates moving away from each other Mid Ocean Ridge (MOR) Great Rift Valley in Africa Convergent Boundary Two plates coming together One usually pushes out on top Produces Mountain ranges and trenches depending on the plate type. Rates of Movement North America away from Europe at about 2.5 cm per year 225 million years ago Pangaea began to break up Movement is slow, about the same rate as your fingernails grow. Summary What is the theory of plate tectonics? The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates. What are the different types of plate boundaries Transform boundaries, divergent boundaries, and convergent boundaries What major event in the earth’s history began 225 million years ago The Supercontinent Pangaea began to break apart