READING QUESTIONS: Chapter 11, Plate Tectonics GEOL 131 Fall 2018 61 pts NAME DUE: Tuesday, November 20 Continental Drift: An Idea Before Its Time (p. 317-321) 1. Fill in the blanks in this sentence from the textbook (p. 317): During the, as better became available, people noticed that the, particularly and, could be fit together like pieces of a jigsaw puzzle. (5 pts) 2. Fill in the blanks in these sentences from the textbook (p. 318): it was when [Wegener] learned that identical had been discovered in rocks from both South America and Africa that his pursuit of became more focused. Wegener learned that most paleontologists agreed that some type of was needed to explain the existence of similar Mesozoic-age life forms on widely landmasses. (4 pts) 3. In the early 20 th century, how did opponents of the continental drift hypothesis explain the presence of identical fossils on separate continents? (3 pts) a. b. c. 4. Fill in the blanks in these sentences from the textbook (p. 319): evidence for a period dating to the late Paleozoic era in southern,,, and... Much of the land that contains evidence of this period of Paleozoic glaciation presently lies within 30 of the, in or climates. (4 pts)
5. What mechanism did Wegener propose for continental drift, and what objection did physicist Harold Jeffreys have to this mechanism? (4 pts) 6. Fill in the blanks in these sentences from the textbook (p. 320): Wegener also incorrectly suggested that the larger and sturdier continents the thinner oceanic crust, much as cut through ice. However, no evidence existed to suggest that the ocean floor was enough to permit passage of the continents without the continents being appreciably in the process. (4 pts) The Theory of Plate Tectonics (p. 321-323) 7. What major ocean floor feature did oceanographers discover the extent of after World War II? 8. Next to each characteristic below, indicate whether it applies to continental lithosphere, oceanic lithosphere, both kinds of lithosphere, or the asthenosphere. Indicate your choice by writing C, O, CO, or A next to each characteristic. (3 pts) a. Cool b. Warm c. Flows d. Bends or breaks e. Mafic in composition f. Felsic in composition
9. Match the name of each type of plate boundary with the arrows that show the kind of motion that occurs there. (3 pts) Transform A. Divergent B. Convergent C. Divergent Plate Boundaries and Seafloor Spreading (p. 323-326) 10. What is the average rate of seafloor spreading in modern oceans? cm/year 11. EXTRA CREDIT: All of Earth s modern ocean floors were created at divergent boundaries within the last 200 million years. Although this seems like a long time, it is only % of Earth history. 12. Fill in the blanks in this sentence from the textbook (p. 324): The primary reason for the position of the oceanic ridge is that newly created oceanic lithosphere is and, therefore, than cooler rocks located away from the ridge axis. (3 pts) 13. Fill in the blanks in these sentences from the textbook (Fig. 13, p. 325): Continental rifting occurs where plate motions produce forces that the lithosphere and promote upwelling in the mantle. Stretching causes the brittle crust to into large that sink, generating a. Continued spreading generates a long, narrow similar to the present-day Red Sea. Eventually, an expansive containing a centrally located is formed by continued seafloor spreading. (4 pts) Convergent Plate Boundaries and Subduction (p. 326-330) 14. Fill in the blanks: The angle at which an oceanic plate subducts depends largely on its and, therefore, its. (2 pts)
15. Match each of the following types of convergent plate boundary to the correct diagram (3 pts): Oceanic-oceanic Oceanic-continental Continental-continental A. B. C. 16. EXTRA CREDIT: List one geographic example of a modern volcanic island arc, and one example of a continental volcanic arc. (2 pts) a. Volcanic island arc: b. Continental volcanic arc: 17. Oceanic lithosphere subducts because it is than the asthenosphere beneath it. Transform Plate Boundaries (p. 330-331) 18. EXTRA CREDIT: List two examples of transform boundaries that cut through continental crust instead of through ocean basins. (2 pts) a. b.
19. On this diagram of a fracture zone along an oceanic ridge, label the segment of the zone that is an active transform boundary by writing transform on one of the three blanks. Testing the Plate Tectonics Model (p. 334-339) 20. What is the age of the oldest sediments recovered by deep-sea drilling? 21. Continental rocks have been discovered that are older than years. 22. Fill in the blanks in these sentences from the textbook (p. 335): Drill cores revealed that sediments are almost entirely on the and that sediment thickness with increasing distance from the ridge. (3 pts) 23. Examine Figure 26 on page 336. In which direction do the Hawaiian Islands become older? (North is toward the top of the figure.) a. Southeast b. North c. Northwest d. Southwest 24. Your answer to the previous question means that the Pacific tectonic plate, on which Hawaii sits, is moving a. Southeast b. North c. Northwest d. Southwest
25. Fill in the blanks in these sentences from the textbook (p. 336-7): some naturally occurring minerals are and are influenced by Earth s. One of the most common is the iron-rich mineral, which is abundant in of basaltic composition as the lava cools, these iron- rich grains become magnetized and themselves in the direction of the existing magnetic of. Once the minerals solidify, the magnetism they possess usually remains in this position. Thus, they act like a because they point toward the position of the magnetic at the time of their formation. Rocks that formed thousands or millions of years ago and contain a of the direction of the magnetic poles at the time of their formation are said to possess. (6 pts) 26. Examine figure 30 on page 338. The white stripes indicate oceanic crust exhibiting normal magnetic polarity, and the colored stripes indicate reversed polarity. How many time intervals of reversed polarity are represented by the oceanic crust in this figure? (Remember that, during each time interval of reversed or normal polarity, two stripes of crust with that polarity are created along divergent boundaries.) Number of time intervals of reversed polarity: 27. Examine Figure 32 on page 340. The youngest ocean floor is closely associated with what ocean floor feature? a. Oceanic ridges b. Subduction zones c. Seamounts d. Continental margins e. All of the above f. None of the above