Appendix M-Deserts

Complete this week’s lab by filling in your responses to the questions from the Geoscience Laboratory. Select answers are provided for you in red font to assist you with your lab work. Although you are only required to respond to the questions in this worksheet, you are encouraged to answer others from the text on your own.

Lab Questions

15.4.Given principles 1–4 on page 265, explain the occurrence of the two contrasting climates illustrated in Figure 15.5.

Warm air and cold air.

15.8.Why are nights in arid lands surprisingly cold? Hint: Think of a feature of the atmosphere that holds daytime heat during the night.

Arid regions typically exhibit surprising differences in daytime/nighttime temperatures.

15.14.What is the prevailing wind direction indicated by the barchan dunes in Figure 15.14?

Answer: From west to east

15.16.Notice in Figure 15.14 that some of the dunes are not perfectly symmetrical like that shown in Figure 15.13. (A) Describe this asymmetry, and (B) try to explain it. Hint: Study the caption to Figure 15.13A.

A constant wind direction produces a dune that is symmetrical in plan view. The windward side is the gentler slope, and the leeward side is the steeper slope.

15.17.On page 278 of the Answer Page draw a topographic profile from coordinates F-6.7 to H.5-10 on the Lakeside quadrangle.

15.18.Which is the steeper side of this dune—the northwest side or the southeast side?

The northwest side.

15.19.Which kind of dune illustrated in Figure 15.15 do you believe you traversed with your topographic profile? Three of the shapes—barchan, parabolic, and transverse—indicate wind direction by their steeper slopes being on their leeward sides.

15.20.From which direction did the wind that fashioned the dunes of the Laeside region blow (NE, NW, SE, or SW)?

Answer: from the northwest

15.22.
A. What kind of rock appears to be upturned around the margins of the salt dome in Figure 15.18—igneous, sedimentary, or metamorphic?

The aridity that promotes precipitation of evaporite minerals also accounts for the durability of chemical sedimentary rocks in deserts.

B. What is the evidence for your answer?

Salt deposits, for example, are quickly dissolved in humid regions, but they endure in the dry atmosphere of deserts.

Lab Summary

Address the following questions in a 100- to 200-word summary:

• Summarize the general principles and purpose of the lab. • Explain how this lab helped you better understand the topics and concepts addressed this week. • Describe what you found challenging about this lab.

• Describe what you found interesting about this lab.

Write your summary here:

The general principles and purpose of the lab is what are the mechanism for the development of desert minerals? What are some of the elements and minerals that form in desert environments? How are salt domes formed? This lab helped me better understand the topics and concepts addressed this week by explaining what are the explanations for deserts ascribed to rain shadows and cold-water coasts? What are two examples of how animals use principles of atmosphere dynamics? What is the practical definition of aridity? What I found challenging about this lab was the geologic history is recorded by features evident on the Lakeside, Nebraska quadrangle. What I found interesting about this lab was the four kinds of sand dunes, and how does each kind record the direction of wind that shaped it.