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Transcript
Chapter 17 Plate Tectonics Structure of the Earth Drifting Continents The Earth’s continents move 16 century mapmaker Abraham Ortelius noticed the “fit” of the continents. 19th century Eduard Sues proposed an ancient landmass named Gondwanaland. 1912 – Alfred Wegener proposed the hypothesis of Continental Drift. Continental Drift Wegener proposed that all continents were once joined in supercontinent called Pangea. He was one of the first to propose that the continents are drifting on the Earth’s surface. Continental Drift Evidence Rock formations (coal beds, sedimentary rocks) Climate evidence (glacial deposits) Fossil evidence (same animals) Shapes of continents Paleomagnetism – The study of the Earth’s magnetic field history through iron bearing rocks. Seafloor spreading In the 1940’s and 1950’s scientists found out that there are mountains in the center of the Atlantic Ocean (Mid-Ocean ridge). Sea floor spreading occurs at the MidOcean ridge and new land is being formed by volcanoes. Scientists used a magnetometer to find that magnetic reversals occur on Earth. Another view of magnetic reversals Seafloor Spreading Scientists also found that there is more sediment on the sea floor as you move away from the Mid-Ocean ridge. Scientists map the age of the rocks on the ocean floor with isochrons. An isochron is line on a map that connects points that have the same age. The Missing Link Sea floor spreading explains how the continents move across the surface. The plates (the rigid mantle) slide across the Asthenosphere. Plate Tectonics Theory of Plate Tectonics states that Earth’s crust and rigid upper mantle are broken into enormous slabs called plates. There about 12 major plates, and some smaller plates. These plates interact at plate boundaries. Plate Tectonics Major unifying Geology theory that explains: Volcanoes Mountain ranges Mid-Atlantic ridge and rift valleys Trenches Island arcs Continental Drift Show video Fearless Planet - last chapter Look see Current continents Plate boundaries Future continents? Earthquakes & Volcanoes Growth of a continent Subducting plates Crashing continents View video Mountains: Ethiopian Highlands Andes Rockies in summer Alps Hotspot Ridge Trench Plate Movements Volcanism Plate movement Inside the Volcano Ring of Fire Ocean Deep Ocean Vents Inside the Volcano Iceland