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Transcript
Plate tectonics Layers of the earth From outside to inside: crust, mantle, outer core, inner core Lithosphere = upper mantle & crust The lithosphere acts as one layer Plate tectonics Lithosphere is divided into several major plates The plates can move and change shape and size The plates are not exactly the same as continents. Interaction of the plates is what we call plate tectonics Plate tectonics Plates move about 5 cm a year (the length your fingernail grows) Plates move because of convection currents in the mantle. Hot material moves up and cool material moves down Effects of the Movement Do you think moving 5 cm makes any difference in the Earth? This small movement builds up great pressure. Seafloor spreading Seafloor = floor at the bottom of the ocean Seafloor spreading = rising magma forces the crust upward and apart, making new seafloor All of the seafloor was made in the last 200 million years Seafloor spreading Effects of plate movement Tectonic plates moving causes: Earthquakes Volcanoes Mountain Building What causes Earthquakes? Evidence for plate tectonics Earthquake patterns: Earthquakes occur most often on plate boundaries Evidence for plate tectonics Paleomagnetism: Scientists can see magnetic patterns in the seafloor This allows us to see how new seafloor has formed over time How can we find out the age of rocks at the bottom of the ocean? Evidence for plate tectonics Ocean Drilling: Scientists can measure the age of the seafloor This lets us see that new seafloor has formed from seafloor spreading recently