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Plate Tectonics Plate Tectonics • • • • A quilt of plates carrying continents and oceans that slide over magma causing changes in features of the earth’s surface Theory of Continental Drift Proven in 1967 – 1968 by scientists Based on a theory by Alfred Wagener Continental Drift • Alfred Wagener proposed the theory in the 1920’s • Based on matching fossils in different world locations • Believed that everything started from a super continent named Pangaea Types of Plate Movement • • • • • • • • Sea-floor spreading Action – magma surfaces from a crack in the plates causing them to push apart Results – causes some volcanic/earthquake activity and a scar-like ridge along the surface of the ocean floor. Example – Mid-Atlantic Ridge Subduction Action – one plate dives under another plate Results – Earthquakes and volcanic activity Example – Pacific Plate under the Asian Plate, the Ring of Fire Colliding and Grinding Plates • • • • • • • • Collision (convergent) Action – one plate crashes into another plate and then continues pushing into it. Results – Formation of mountains, earthquakes Example – Indian Sub-continent into the Asian Plate. Himalaya Mountains Grinding Action – two plates slipping/sliding along an outer edge Results – earthquakes, folding and faulting, some volcanic activity Example – Pacific and North American Plates. California, Washington, and Oregon earthquake activity Explanation • These types of actions along with Hot Spots (Hawaii) change the surface of the earth from internal forces