WATER, WIND, AND TIME: Desert Landforms

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Chapter Outline

  • 18.1

    Desert Landforms and Processes

  • 18.2

    Desert Landscapes

  • 18.3

    Geographic Perspectives: Shrinking Desert Lakes
Uluru (or Ayers Rock) rises above a sea of sand in the Northern Territory in central Australia. It is a weathered mass of sandstone that is some 600 million years old.
(Per-Andre Hoffmann/Picture Press/Getty Images)

LIVING PHYSICAL GEOGRAPHY

  • What are prehistoric petroglyphs and why were they made?

  • How do sand dunes sing?

  • What is a sand sea?

  • Why has the Aral Sea nearly disappeared?

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THE BIG PICTURE

Desert landforms are shaped by flowing water and wind. Desert lakes and their ecosystems are changed when people divert water from them.

LEARNING GOALS

After reading this chapter, you will be able to:

  • 18.1

    Provide examples of desert landforms and discuss the processes that form them.

  • 18.2

    Explain how different desert landscapes develop.

  • 18.3

    Assess the effect of water diversions on desert lakes.

THE HUMAN SPHERE:

Flooding in the World’s Driest Place

ANTOFAGASTA, A PORT CITY IN NORTHERN CHILE with a population of about 360,000, is the fourth largest city in Chile. It is located in the world’s driest place, the Atacama Desert (Figure 18.1).

Figure 18.1

Factors responsible for Antofagasta’s aridity. The aridity of the Atacama Desert is a result of several factors. The desert is located in the subtropical high-pressure zone (see Section 4.3) as well as in the rain shadow created by the Andes (see Section 3.3). In addition, the cold Peru (Humboldt) Current is slow to evaporate, leaving little moisture in the air.
(© Walter Bibikow/AWL Images/Getty Images)

Antofagasta receives only 4 mm (0.16 in) of rain each year, on average. Like most desert regions we will explore in this chapter, however, the city is built on a surface created by flowing water. Paradoxically, the citizens of Antofagasta must protect it against flooding and debris flows. On rare occasions during strong El Niño years, flooding rains fill the normally dry canyons to the east of the city with raging torrents of water. The bare hills have little to no vegetation to anchor soils, and the canyons turn into slurries of mud that flow down onto the alluvial fans on which the city is built. Such flooding has happened seven times in the city’s history. The most recent flood event was in 1991, when more than 100 people died.

This chapter explores desert landforms and the processes that create them. We also turn our attention to different types of desert landscapes and see how each develops. Finally, we visit shrinking desert lakes and examine the anthropogenic factors that threaten them.

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