Review Questions for Program #23: Glaciers
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Program #23. If you are unsure of an answer, give your best
intelligent guess.
1. What are glaciers?
Massive sheets of ice that move, grow, and shrink according to climate conditions.
2. Where are two general places where glaciers are found on Earth?
At high altitudes here the air is cooler, and at certain polar regions where ice caps are moderated.
3. What kind of snow accumulation and melt budget produces a growing glacier?
If more snow accumulates in a year than melts away, a glacier grows. If more snow melts in a year than falls, then the glacier shrinks.
4. Describe how snow converts to glacial ice.
As snow continues to fall, that resting in the deeper layers become compacted. The snow loses its fluffiness, and recrystallizes to "firn," which is ice made up of tiny crystals.
5. What are the conditions under which ice will shatter?
When ice is found near the surface of a glacier, or with pressure that is applied very rapidly.
6. What are the conditions under which ice will bend and flow?
Generally, for ice that is buried deeply or applied slowly.
7. Where does a valley glacier flow fastest?
At the surface and middle of a valley glacier.
8. What is the difference in how the two types of glaciers advance?
Mountain glaciers slide down hill by way of gravity; continental glaciers generally remain thicker at the center of the ice cap, which forces the glacier to slide out toward the edges.
9. What are some erosional features of glaciation?
U-shaped valleys, hanging valleys, cirques, aretes, tarns, kettle lakes
10. Where can "till" accumulate in glaciers?
It accumulates on the margins as moraines; also at the base of a glacier as fragments are wedged out and dragged along.
11. What are ice ages?
Periods during which massive continental ice sheets grow to cover significant portions of continents located near to polar latitudes.
12. How are ice ages related to sea level?
During ice ages, sea level tends to fall. During interglacial periods (when Earth wams up), sea level rises.
13. What are some possible explanations for why ice ages occur?
1. Plate tectonics moving continents to polar
latitudes
2. The arrangement of ocean circulation
currents
3. The composition of Earth's atmosphere
(related to Greenhouse Effect)
4. Milankovitch cycles (the shape of Earth's
orbit, tilt of Earth's axis, the precession of Earth's axis)
14. Why do landmasses rise when glaciers melt back?
Because of isostacy. Previously the weight of the ice cap pushed down on the crust. With the melting of an ice cap, the crust rebounds and rises back.
15. What information can be obtained by drilling into glaciers?
Information of contaminants or pollutants in the atmosphere in Earth's past history preserved as bubbles in ice; timing of major volcanic eruptions through the preservation of fine volcanic ash layers.