Exercise 42 - Part I (Page 292): Question 1, 2, and 3 (all parts) Review pages 495-497 in the textbook.

The isolated dunes in the desert near the Salton Sea are moving over a surface that is only thinly covered with sand.

1. What are the braided markings on the faces of the fans?

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2a. Look at the upper portions and margins of the alluvial fans shown on the map and in the stereogram (especially the alluvial fan at the mouth of "Grotto Canyon"). In recent years, does erosion OR deposition appear to have been more prominent at the tops of these fans? (Hint: look carefully for evidence of either recent deposition or recent down cutting at the tops of the fans. For example, gullies cut into the tops of the fans are evidence of erosion; the presence or absence of desert varnish can also provide clues as to the location of recent activity on the fans.)

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2b. How can you tell?

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3. Suggest a reason and explain why the alluvial fans here vary so greatly in size.

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1a. What kind of sand dunes appear to be most common in this dune field?

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1b. How do you know?

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4a. From which direction does the prevailing wind blow? (The top of the map is north.)

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3b. How can you tell?

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4c. If the prevailing wind direction remains the same, with time, in which direction will these dunes move?

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Part 2: Lesson 13 Short Answer

Describe the characteristics found in arid environments that contribute to the formation of unique desert landscapes. Be sure to analyze in detail how wind and water impact these landscapes by including two specific examples of arid landforms.

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