EARTH: AN INTRODUCTION TO PHYSICAL GEOLOGY

Chapter 2: Plate Tectonics: A Scientific Revolution Unfolds

Chapter Test

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Choose the best possible answer to the following questions for all of "Chapter 2."

1.

The following figure illustrates what geologists believe Pangaea probably looked like. By selecting the correct response, label some of the present-day land masses that once comprised this supercontinent.  

For each item below, use the pull-down menu to select the letter that labels the correct part of the image.

The letters A through D appear on an image associated with this question.

2. One of the main objections to Wegener's hypothesis was his inability to provide an acceptable ____________ for continental drift.  

3. Examine the plate tectonics information at this University of California-Berkeley Museum of Paleontology site. What mechanism did Alfred Wegener use to explain the breakup of Pangaea?  

4. According to the information presented at the site referenced in Question 3, in 1929 Arthur Holmes devised a theory that plate tectonics is driven by the __________.  

5. The best way to determine the true shape of a continent is to trace the outer boundary of its continental shelf.  
 
6. Seafloor spreading is the mechanism that has produced the floor of the Atlantic Ocean.  
 
7. The idea that Earth's magnetic poles have migrated through time is known as polar wandering.  
 
8. The apparent movement of Earth's magnetic poles over time is referred to as ____________.  

9. Magnetic minerals lose their magnetism when heated to a temperature above the mineral's ______________.  

10. Older portions of the sea floor are carried into Earth's core in regions where trenches occur in the deep ocean floor.  
 
11. The "Ring of Fire" is an area of earthquake and volcanic activity that encircles the Pacific ocean basin.  
 
12. When rocks exhibit the same magnetism as the present magnetic field they are said to possess reverse polarity.  
 
13. The oldest oceanic crust is located at ocean ridge crests.  
 
14. The largest single rigid slab of Earth's outer shell is the Pacific plate.  
 
15. As oceanic crust moves away from a spreading center, it becomes cooler and less dense.  
 
16. All major interactions among individual lithospheric plates occur along their boundaries.  
 
17. The theory of plate tectonics holds that Earth's rigid outer shell consists of about ____________ major lithospheric plates.  

18. Along some divergent plate boundaries, oceanic crust is being consumed in subduction zones.  
 
19. Along divergent plate boundaries, the upwelling of material from the mantle creates new sea floor.  
 
20. As a consequence of plate tectonics, the total surface area of Earth is decreasing.  
 
21. Transform fault boundaries are located where plates grind past each other without either generating new lithosphere or consuming old lithosphere.  
 
22. Most of Earth's seismic activity, volcanism, and mountain building occur along ____________.  

23. Complex mountain systems such as the Alps, Appalachians, and Himalayas are the result of ____________.  

24. A ___________ plate boundary is where plates move together, causing one of the slabs of lithosphere to be consumed into the mantle as it descends beneath an overriding plate.  

25. The best approximation of the true outer boundary of the continents is the seaward edge of the ____________.  

26. The Aleutian, Mariana, and Tonga islands are examples of ____________.  

27. The Red Sea is believed to be the site of a recently formed ____________.  

28. Most deep-focus earthquakes occur in association with ____________.  

29. The age of the deepest sediment in an ocean basin ____________ with increasing distance from the oceanic ridge.  

30. Explore this United States Geological Survey (USGS) site on hot spots. According to the information presented, hot spots are __________.  

31. The Hawaiian Islands become younger to the east-southeast (Hawaii is the youngest, while the seamounts to the west-northwest are oldest). Assuming the hot spot is stationary, and the the entire chain of islands was formed by this hot spot, which direction is the Pacific plate moving?  

32. According to the information about the long trail of Hawaiian hotspots presented at the USGS website in Question 30, toward which direction was the Pacific plate moving when the Emperor Seamount chain was forming over the Hawaiian hot spot?  

33. Hot spot volcanics in the oceans (e.g., Hawaii) consist almost entirely of mafic rocks, but on the continents (e.g., Yellowstone) the material consists of a mix of mafic and felsic rocks. The reason for this difference is that __________.  

34. The Red Sea is believed to be the site of a recently formed convergent plate boundary.  
 
35. In North America, the Cascade Range and Sierra Nevada system are continental volcanic arcs associated with the subduction of oceanic lithosphere.  
 
36. There is a close association between deep-focus earthquakes and ocean ridges.  
 
37. The unequal distribution of heat inside Earth generates some type of thermal convection in the crust which ultimately drives plate motion.  
 
38. The Aleutian, Mariana, and Tonga islands are volcanic island arcs associated with oceanic-oceanic plate convergence.  
 
39. Oceanic lithosphere is consumed at convergent plate boundaries.  
 
40. Most large tectonic plates containing continental crust also contain oceanic crust.  
 
41. Most deep-focus earthquakes are associated with subduction zones.  
 
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