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Chapter 21: Dry Regions: The Geology of Deserts

Geotours

Download Geotours.

Getting Started :

If you haven’t done it already, download Google Earth™ and install it on your computer.
If you haven’t done it already, download the Geotours.kmz file and save a copy to your desktop. (The Geotours.kmz file contains the Geotours for all chapters, so you only need to download this once!)
By downloading Geotours.kmz you acknowledge that it was created solely to accompany Steve Marshak's Earth: Portrait of a Planet and Essentials of Geology and is limited to use with only Steve Marshak's Earth: Portrait of a Planet and Essentials of Geology and may not be reproduced, stored in a retrieval system, or transmitted in any form by any means for any other purpose without the written permission of the publisher.
Double-click the Geotours.kmz file and Google Earth™ will open automatically.
In the left-hand sidebar you will see a Places menu, and in the Temporary Places folder you will see an EARTH_3e.kmz file. Double-click the file and you will see a list of Geotours for each chapter.
Then open the Geotour folder you want to explore! If you’d like to read more about the features of Geotours see Using Geotours, or go to our Helpful Resources section.

STOPS ON GEOTOUR 21: Desert Landscapes

Sand Dunes, Namib Desert, Africa
Uluru (Ayers Rock), Australia

See also Worksheet Problem 1
"What a Geologist Sees" Geofeatures: Ayers Rock, The Olgas, and Syncline Development

Atacama Desert near Chala, Peru

See also Worksheet Problem 2

Tarim Basin of Western China

See also Worksheet Problem 3

Dry Wash in Arizona

See also Worksheet Problem 4

Urbanizing a Desert, Tucson, Arizona
Playa in Death Valley, California

See also Worksheet Problems 5-6

Buttes of Monument Valley, Arizona

See also Worksheet Problem 7

Sand Sea in the Sahara, Egypt

GEOTOUR 21 WORKSHEET

In the desert, the unvegetated land surface lies exposed, so landform shapes are clear and dramatic. High-resolution images allow you to see cliffs, dunes, fans, and even individual boulders. Here, we tour several deserts to see the variety of landscapes. Zoom out into space to remind yourself of where you are on the globe.

Uluru (Ayers Rock), Australia
1. Double-click and check the box next to one of the placemarks labeled Problem 1. You’ll fly to the site of the Uluru (Ayers Rock) in Australia.

(a) To obtain a sense of Uluru’s size, use the Measuring Tool to measure the distance between the placemarks labeled Problem 1 (in km).

(b) Using the Hand Tool, determine the elevation difference between the highest point on Uluru (in m) and the surface of the nearby desert.

(c) The lines on Uluru are the traces of the vertical sandstone beds. What is the compass direction (e.g., N–S, NW–SE) that these beds strike?

(d) If you zoom up to an elevation of about 15 km, you will see that the texture (surface character) of the desert landscape for a distance of about 1–2.5 km around Uluru differs from that of regions further away (e.g., 5 km from Uluru). Describe and explain this difference.

Note: An abandoned airstrip lies on the NE side of the rock. Desert plants are starting to cover it up

Atacama Desert near Chala, Peru
2. Double-click and check the box next to one of the placemarks labeled Problem 2 to see the Atacama Desert.

(a) What evidence in the vicinity of the placemark for Problem 2a shows that the dominant agent of erosion, even here in the driest place on earth, is running water?

(b) What have nearby residents done to address flooding hazard posed by the large wash labeled with the placemark for Problem 2b?

Tarim Basin of Western China
3. Despite its appearance in Image G21.5, the Tarim Basin does not extend forever. To obtain a sense of scale for this large basin, double-click and check the box next to one of the placemarks labeled Problem 3.

(a) Use the Measuring Tool to determine the distance between the following placemarks (in km):

(b) Zoom to an elevation of about 75 km over the center of the desert (i.e., to a point about 150 km NE of the Image G21.5 placemark). You see a vast field of longitudinal dunes. Keeping in mind the dune type, what is the trend of the “prevailing winds” (steady winds that consistently blow in the same direction) here: N to S, NE to SW, SE to NW, or NW to SE?

(Note: Look at the map of prevailing winds in Chapter 20, and compare your observation to the wind directions shown on the map for the latitude of the Tarim Desert. Read the related section in Chapter 20 to see why prevailing winds exist.)

(c) There are two north-flowing intermittent streams in the region west of the placemark for Image G21.5. The closer one (about 75–80 km west of the placemark) terminates in the middle of the desert, even though the land slopes gently north. Why?

Dry Wash in Arizona
4. Double-click and check the box next to the Problem 4 placemark. You will fly to a region in Arizona where numerous small dry washes are arranged in a dendritic pattern.

(a) Give the compass direction that water would flow in the intermittent streams near the placemark for Problem 4. (Hint: Rotate the view to closer to horizontal to see the landscape.)

(b) Zoom out to an elevation of 50 km. You can now see that the washes at the placemark for Problem 4 drain into a larger dry wash that flows west. This wash in turn flows into a larger wash that flows south. (This wash is about 6.5 miles due west of the placemark for Problem 4.) Note the green fields that occur in the floodplain of this wash. About 10 km upstream of the confluence you will see the community of Rio Verde. Zoom down and you can see green golf courses and water-filled ponds. Where does the water come from?

Playa in Death Valley, California
5. Double-click and check the box next to one of the placemarks labeled Problem 5. Identify the landforms highlighted by the Problem 5a and b placemarks.

6. Use the Hand Tool to measure various elevations on the Death Valley floor.

(a) What value (in m) does Google Earth^TM provide for this area?

(b) Given what you know about the elevation of Death Valley in this area, is the elevation for Problem 5a correct? (Note: This is a limitation of Google Earth^TM).

Buttes of Monument Valley, Arizona
7. Double-click and check the box next to the placemark labeled Problem 7. You will fly to Monument Valley in Arizona, site of many western movies because of its spectacular scenery.

(a) Use the Hand Tool to determine the relief of the butte highlighted by the Problem 7 placemark (m).

(b) How is sediment removed from this area, and in which direction does the sediment move?

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StudySpace: Chemistry 2e.