Chapter 21

1. The ice that makes up a glacier is generally equivalent to: loosely packed snow like loose sediment. tightly packed snow like a sedimentary rock. interlocking crystals similar to a metamorphic rock. layered ice with air pockets like a vesicular basalt.

2. Today, continental ice sheets occur: on Greenland. on Antarctica. on peaks in the Himalaya mountains. on peaks in the Swiss Alps. All of the above. A and B only.

3. What causes glaciers to flow? gravity magnetism centripetal force tectonic force

4. Continental glaciers hold what percent of the world’s freshwater? 35% 50% 60% 75%

5. Which processes result in glacial ablation? melting iceberg calving sublimation wind erosion All of the above.

6. If a glacier is in equilibrium (accumulation = ablation), what occurs at the terminus? Sediment is deposited. The underlying bedrock is eroded. Neither erosion nor deposition occurs.

7. What happens during glacial retreat? The glacier flows back to its origin. Less ice is supplied to the terminus. The glacier ceases to flow.

8. Some tropical mountains host valley glaciers, which is sustainable as long as: accumulation > ablation. accumulation = ablation. accumulation < ablation. either A or B.

9. Which part of a valley glacier flows the fastest? along the base along the sides in the center All areas flow at the same rate.

10. What do arêtes, cirques, hanging valleys, fjords, and U-shaped valleys all have in common? A. All only form from continental-scale glaciations. B. All are only found in the Northern Hemisphere. C. All are erosional features. D. All of these answers are correct.

11. Compared to a stream-modified terrain, a glacially modified terrain has ___________ mountain profiles and _____________ valleys. A. sharp; V-shaped B. sharp; U-Shaped C. rounded; V-shaped D. rounded; U-shaped

12. Which sediment characteristics best describe glacial till? A. well sorted, poorly stratified B. well sorted, well stratified C. poorly sorted, well stratified D. poorly sorted, poorly stratified

13. What can erratics tell you about glaciers? the age of a glacier where a glacier came from the rate of glacier movement All of the above.

14. Which of the following features do not indicate the direction of glacier flow? A. roche moutonée B. glacial striations C. eskers D. drumlins

15. Which type of moraine indicates the furthest advance of ice? lateral moraine medial moraine ground moraine terminal moraine

16. It has been recognized that regions around the St 16. It has been recognized that regions around the St. Lawrence seaway in northeastern North America experience frequent small magnitude seismic events despite being located near a passive margin. How can this seismic activity be explained? A. This activity is related to the isostatic rebound of the continental crust, due to the removal of a large ice mass since the last glacial maximum. B. This activity is related to the reactivation of an ancient subduction zone due to increased tectonic activity in Iceland. C. This activity is a result of volcanic eruptions beneath the surface of the Great Lakes, which has generated concerns about a major tsunami in the area. D. All of these are true. E. None of these are true.

17. During the last ice age there was a large ice sheet over much of Canada and the northern United States. What was the effect on global sea levels? Sea level was higher. Sea level was lower. Sea level was the same as today.

18. One million years ago ice sheets covered much of Earth’s land surface during an ice age. How did this affect the salinity of the oceans? Oceans were saltier. Oceans were less salty. Salinity was the same as today.

19. Which of the following relationships best explains the link between global sea level and polar ice extent? A. When temperatures rise, sea levels fall and the oceans become more saline. B. When temperatures drop, sea levels fall and the oceans become less saline. C. When temperatures rise, sea levels rise and the oceans become more saline. D. When temperatures drop, sea levels drop and the oceans become more saline.

20. The most recent of the Pleistocene glaciations, the ___ is the best preserved. Nebraskan Kansan Wisconsinan Illinoisan