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Chapter 13 – Plate Tectonics Review Questions

  1. Explain the theory of continental drift. Who developed it, when, what was it about?
  2. Alfred Wegner developed the theory of continental drift which states that all the continents once fit together as one big continent called Pangaea (all land).

  3. What was the evidence used to support the theory of continental drift?
  4. There were four pieces of evidence used: 1) the fit of the continents, especially So. America and Africa, 2) rock structure due to glaciation, 3) fossils such as Mesosaurus and Glossopteris, 4) ancient climates such as glacial history where it is now tropical.

  5. What layers of the earth make up the lithosphere?
  6. The crust and the upper mantle

  7. What layers of the earth make up the asthenosphere?
  8. The lower part of the upper mantle.

  9. What layers of the earth make up the plates?
  10. The lithosphere (crust and upper mantle)

  11. What was one of the controversies challenging the theory of continental drift? How was this challenge overruled?
  12. 1) The fit of the continents. People argued that the shorelines are constantly eroding. This was defeated by showing that the continents fit at the continental shelf under water not at the shoreline.
    2) Fossil evidence. People argued that there was a land bridge which enabled the Mesosaurus to cross the ocean. This was defeated due to lack of evidence of a land bridge in the middle of the Atlantic Ocean.

  13. What type of crust (oceanic, continental) make up the North American Plate?
  14. Continental

  15. What type of crust (oceanic, continental) make up the Pacific Plate?
  16. Oceanic

  17. What are plate boundaries? What is occurring there?
  18. Plate boundaries are locations in which two or more plates meet. Depending on the type of plate (oceanic or continental) may things can occur such as mountain building to subduction and volcanoes.

  19. What are the different types of plate boundaries? Be able to describe what is occurring at each, and give one example of where this is happening.
  20. Diverging, converging, transform - be sure to review your notes from class on this****

  21. What type (depth) of earthquakes occur at subduction boundaries? (Think about your lab.)
  22. Deep earthquakes occur where at subduction boundaries like north of the Aleutian trench. As the crust is getting pulled down further, causing friction at a deeper depth.

  23. The volcanoes of the Andes Mountains, as well as Mount St. Helens and Mt. Rainier are volcanoes associated with what type of plate boundary?
  24. Converging boundary between oceanic and continental crust

  25. Describe the relationship between age of the volcanic rock and the distance from the spreading center.
  26. As the distance from the spreading center increases, the age of the rock also increases.

  27. Why would seafloor always be younger than continents?
  28. New crust is forming at the ridges in the ocean and depositing the older crust on land.

  29. What is the difference in density between the continental crust and the oceanic crust: What is the significance of this?
  30. Continental crust is less dense than oceanic crust. When a lower density continental plate converges with a high density oceanic plate the higher density oceanic plate will subduct (go under) the continental plate.

  31. What is the relationship between the spreading centers and the deep ocean trenches?
  32. At spreading centers new crust is being produced, and at the trenches the older crust is being recycled through subduction.

  33. Ocean floor is continuously being made where?
  34. At the mid-ocean ridges.

  35. What type of feature are the mid-ocean ridges? Can this same feature be found outside on an ocean?
  36. Rift. Yes, in rift valleys such as in East Africa.

  37. What is the mechanism behind movement of the plates?
    Convection currents