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8. Identify the features indicated with the following letters and briefly describe how they formed. (Hint: Refer to Figure 9.2.) Letter C: Letter D: 9. Assume that erosion continues in the area without interruption. How might the area look millions of years from now? Glacial abrasion created the scratches and grooves in this bedrock. A Figure 9.5 Moving glacial ice, armed with sediment, acts like sandpaper, scratching and polishing rock and creating glacial striations. (Photo by Michael Collier) 9.3 Glaciers and Ice Sheets Contrast alpine (valley) glaciers and ice sheets. Present-day glaciers cover nearly 10 percent of Earth's land area At the height of the Quaternary Ice Age, gla- ciers were three times more extensive than they are today. These moving masses of ice create many unique landforms and are part of an important link in the rock cycle in which the products of weathering are trans- ported and deposited as sediment. A glacier is a thick ice mass that, over hundreds or thousands of years, forms on land as the yearly snow- fall exceeds the quantity of ice lost by melting. A glacier appears to be motionless, but it is not; glaciers move very slowly. Thousands of glaciers exist in lofty moun- tain areas, where they usually follow valleys originally occupied by streams. Because of their settings, these moving ice masses are termed valley glaciers, or alpine glaciers. Ice sheets (sometimes called continental glaciers) exist on a much larger scale than valley glaciers. These enor- mous masses flow out in all directions from one or more snow-accumulation centers and completely obscure all but the highest areas of underlying terrain. Presently each of Earth's polar regions supports an ice sheet- Greenland in the Northern Hemisphere and Antarctica in the Southern Hemisphere. Glacial erosion and deposition leave unmistakable imprints on Earth's surface (Figure 9.5). In regions once covered by ice sheets, glacially scoured surfaces and sub- dued terrain dominate. By contrast, erosion caused by alpine glaciers accentuates the irregular mountainous topography, often producing spectacular scenery char- acterized by sharp, angular features. Glacial deposits are usually visible in both settings. ©2019 Pearson Education, Inc.