THE WORK OF ICE: The Cryosphere and Glacial Landforms

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Chapter Outline

17.1

Frozen Ground: Periglacial Environments
17.2

About Glaciers
17.3

Carving by Ice: Glacial Erosion
17.4

Building by Ice: Glacial Deposition
17.5

Geographic Perspectives: Polar Ice Sheets and Sea Level

These piedmont glaciers are spilling into a valley on Axel Heiberg Island in the Canadian Arctic. Glacial ice flows downhill, and as it does so, the ice carves into the bedrock below.

(© Dr. Juerg Alean/Science Source)

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LIVING PHYSICAL GEOGRAPHY

Why are bones and tusks of extinct mammoths appearing throughout Siberia?
Why are explosive gases seeping from Arctic lakes?
How do glaciers form?
How does the soft ice of a glacier carve into solid bedrock?
How did Yosemite Valley form?

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THE BIG PICTURE

Perpetually frozen ground and glaciers create unique landforms. The loss of ice on Greenland and Antarctica could cause significant sea-level rise.

LEARNING GOALS

After reading this chapter, you will be able to:

17.1

Identify features unique to areas with permanently frozen soils and explain environmental changes taking place in those areas.
17.2

Explain how glaciers form and move and describe different glacier types and their geographic settings.
17.3

Explain how glaciers cut into rocks and identify landforms caused by glacial erosion.
17.4

Identify landforms created from glacial sediments and explain how they formed.
17.5

Assess the role of polar ice sheets in current and future sea-level changes and explain why sea-level rise presents problems for human society.

THE HUMAN SPHERE:

The Mammoth Hunters

FOR 5 MILLION YEARS, the woolly mammoth (Mammuthus primigenius)—a close relative of the modern African elephant—roamed across much of the Northern Hemisphere by the millions. By about 9,600 years ago, however, all mainland mammoth populations in North America and Eurasia were gone. The last remaining mammoth holdout was Wrangel Island, in northeastern Eurasia. That island’s mammoth population disappeared about 4,000 years ago, right after humans colonized the island. Changing climate and human hunting pressure were the main causes of the extinction of the mammoth and many other large animals that also lived at that time.

Question 17.1

Why are bones and tusks of extinct mammoths appearing throughout Siberia?

When ancient mammoths died, their bones were preserved in frozen northern soils. Now, as the soils thaw, the bones are being exposed.

The remains of some mammoths have been preserved in the frozen northern soils. Now the cryosphere—the frozen portion of the hydrosphere—is rapidly changing. High latitudes are warming at twice the rate of the midlatitudes because of the ice-albedo positive feedback (see Section 6.4). As the frozen soils thaw, the mammoth remains become exposed, and scientists and collectors can find them (Figure 17.1).

Figure 17.1

Mammoth remains. Preserved mammoth tusks, such as these found in Siberia, provide data for scientists studying these ancient animals, and they are prized for their ivory by collectors. Tusks of this size sell for about $100,000 each. An estimated 50 tons of mammoth bones are found each year in Russia.

This chapter explores the cryosphere, in the context of both landforms and changing climate. We first explore periglacial landscapes, those that are unglaciated but perpetually frozen. We then examine how glaciers develop and begin moving, and we visit landforms resulting from the movement of glaciers. Finally, we explore Earth’s two enormous ice sheets, on Greenland and on Antarctica, and their current and projected contributions to sea-level rise.

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