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Earth Science

Earth Science. Coach Williams Room 310B. Chapter 17. Plate Tectonics. Section 17.1: Drifting Continents. Objectives Describe one piece of early evidence that led people to suggest the Earth’s continents my have once been joined. Discuss evidence of continental drift

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Earth Science

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  1. Earth Science Coach Williams Room 310B

  2. Chapter 17 • Plate Tectonics

  3. Section 17.1: Drifting Continents Objectives • Describe one piece of early evidence that led people to suggest the Earth’s continents my have once been joined. • Discuss evidence of continental drift • Explain why continental drift was not accepted when it was first proposed.

  4. Early Observations • Fit of continents across Atlantic Ocean • Gondwanaland: southern continents

  5. Gondwanaland

  6. Continental Drift • Theory that Earth’s continents were once joined. • Continents had slowly drifted apart • Pangaea: “all the Earth”

  7. Continental Drift Evidence • Rocks: similar rocks • Fossils: animal/plant remains • Ancient Climate: coal in Antarctica

  8. Rejected Hypothesis • 2 Reasons the theory was rejected • 1) What forces could cause them to move? • 2) How could continents move and not shatter?

  9. Section 17.2: Seafloor Spreading Objectives • Summarize the evidence that led to the discovery of seafloor spreading. • Explain the significance of magnetic patterns on the seafloor. • Explain the process of seafloor spreading.

  10. Help From Technology • Sonar- sound waves to determine depth • Magnetometer- detects changes in magnetic fields • Map the ocean floor

  11. Ocean Floor Topography • Mountain ranges (ridges), trenches • Earthquakes & volcanoes

  12. Ocean Floor Topography

  13. Ocean Rocks and Sediments • Varying ages of rocks: pattern • Younger rocks near ridges • Older rocks farther away • Sediments • Thinner than continental crust • Thickness increased farther away from ridge

  14. Magnetism • Paleomagnetism: study of magnetic record • Basalt(Iron) = compass needle • Magnetic reversal: change in Earth’s magnetic field • Magnetic symmetry: matching strips on each side of ridge

  15. Seafloor Spreading • New crust created at ridges • Crust is destroyed at trenches • Magma comes out of ridges • New rock pushes crust outward • Provided evidence for continental drift

  16. Seafloor Spreading

  17. Seafloor Spreading

  18. Seafloor Spreading

  19. Section 17.3: Theory of Plate Tectonics Objectives: • Explain the theory of plate tectonics • Compare/contrast the three types of plate boundaries and the features associated with each.

  20. Theory of Plate Tectonics • Earth’s crust: large slabs called plates • Major and smaller plates

  21. Earth’s Plates

  22. Plate Boundaries • Plate boundaries: where plates meet • Divergent • Convergent • Transform

  23. Plate Boundaries

  24. Plate Boundaries

  25. Divergent Plate Boundaries • Plates moving apart • Most on ocean ridges • Rift valley: narrow valley along divergent boundary

  26. Convergent Plate Boundaries • Plates moving together • Oceanic crust – oceanic crust: volcanoes • Oceanic crust – continental crust: volcanoes • Continental crust – continental crust: mountains • Subduction- one plate goes below the other

  27. Convergent Plate Boundary

  28. Transform Plate Boundaries • Plates slide horizontally

  29. Section 17.4: Cause of Plate Motions Objectives: • Explain the process of convection • Summarize how convection in the mantle is related to the movements of tectonic plates • Compare/contrast the processes of ridge push and slab pull

  30. Mantle Convection • Convection: movement due to temperature differences • Mantle has convection currents • Currents move plates • Ridge push- weight of ridge pushes plate down • Slab pull- weight of plate pulls plate down

  31. Push and Pull

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