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38. The oceanic crust is 49. Which type of plate boundary was responsible for the formation
a. thicker than the continental crust. of the Japanese Islands?
b. found under the continental crust. a. Divergent
c. thinner than the continental crust. b. Ocean to ocean convergence
d. the same in its properties as the continental crust. c. Continental to continental convergence
39. Seismic waves that do not travel through liquid are d. Transform
a. P-waves. 50. A famous transform boundary in the United States is the
b. S-waves. a. Rocky Mountains fault.
c. both P- and S-waves. b. Mississippi fault.
d. surface waves. c. San Andreas fault.
40. The fastest seismic wave is the d. San Jose fault.
a. P-wave. 51. Plate movement is measured by
b. S-wave. a. reflected laser light experiments.
c. P- and S-waves are equally fast. b. age of sediments and fossils.
d. surface wave. c. analysis of magnetic patterns in rocks.
41. Information about the composition and nature of the mantle d. All of the above are correct.
does not come from 52. Islands that form when melted subducted material rises through
a. seismological data. the plates above sea level are called
b. meteorite studies. a. Pacific islands.
c. debris ejected from volcanoes. b. arc islands.
d. samples obtained from drilling. c. convergence islands.
42. Primary information about the nature of the core is provided by d. plate islands.
a. seismological data.
b. meteorite studies. Answers
c. debris ejected from volcanoes. 1. a 2. b 3. c 4. a 5. b 6. b 7. a 8. d 9. b 10. c 11. d 12. d 13. b
d. samples obtained from drilling. 14. c 15. a 16. b 17. c 18. b 19. a 20. c 21. a 22. b 23. c 24. a
43. The asthenosphere is not defined as 25. a 26. b 27. a 28. a 29. a 30. c 31. b 32. a 33. d 34. b 35. b
a. rigid. 36. b 37. d 38. c 39. b 40. a 41. d 42. a 43. a 44. b 45. a 46. c
b. plastic. 47. b 48. c 49. b 50. c 51. d 52. b
c. mobile.
d. elastic.
QUESTIONS FOR THOUGHT
44. Earth’s magnetic field is thought to be generated by
a. seismic waves throughout Earth.
b. electrical currents in the core. 1. Describe one theory of how Earth came to have a core composed
c. electrical currents in the crust. mostly of iron. What evidence provides information about the
d. electrical currents in the asthenosphere. nature of Earth’s core?
45. Studies of the Mid-Atlantic Ridge provided evidence of 2. Briefly describe the internal composition and structure of the
a. seafloor spreading. (a) core, (b) mantle, and (c) crust of Earth.
b. seafloor closing. 3. What is the asthenosphere? Why is it important in modern
c. ancient shipwrecks. understandings of Earth?
d. early humans.
4. Describe the parts of Earth included in the (a) lithosphere,
46. Evidence that supports seafloor spreading does not include the (b) asthenosphere, (c) crust, and (d) mantle.
a. earthquakes occurring along the crest of the Mid-Atlantic
5. What is continental drift? How is it different from plate tectonics?
Ridge.
6. Rocks, sediments, and fossils around an oceanic ridge have a
b. presence of rift along the crest of the Mid-Atlantic Ridge.
pattern concerning their ages. What is the pattern? Explain what
c. younger sediments near the continents.
the pattern means.
d. discovery of identical magnetic patterns in rocks on both
7. Describe the origin of the magnetic strip patterns found in the
sides of the ridge.
rocks along an oceanic ridge.
47. A geologic feature that was produced by divergent boundaries is
8. Explain why ancient rocks are not found on the seafloor.
a. the Alps.
b. the Mid-Atlantic Ridge. 9. Describe the three major types of plate boundaries and what
c. the Marianas Trench. happens at each.
d. Japan. 10. What is an island arc? Where are they found? Explain why they
48. Which type of plate boundary accounts for the formation of the are found at this location.
Appalachian Mountains? 11. Briefly describe a model that explains how Earth developed a
a. Divergent layered internal structure.
b. Ocean to continental convergence 12. Briefly describe the theory of plate tectonics and how it accounts
c. Continental to continental convergence for the existence of certain geologic features.
d. Transform
13. What is an oceanic trench? What is the relationship of trenches
to major plate boundaries? Explain this relationship.
474 CHAPTER 18 Plate Tectonics 18-20