A Dry, Hot Land

Where is the world’s largest desert?

1 Unless you live in the western part of the United States, you may consider deserts to be exotic, rare places. Actually, deserts are very common, covering nearly onethird of Earth’s land surface. Although lack of precipitation is the most obvious characteristic of desert regions—they receive less than ten inches per year— deserts also have high rates of evaporation. What little precipitation does fall is quickly absorbed back into the atmosphere.

2 Because of this lack of moisture, deserts can be very hot during the day. Water has a natural cooling effect, but without it, the sun cooks the land. In some deserts, temperatures are regularly as high as 130 degrees Fahrenheit. However, after the sun goes down, all that heat escapes from the desert ground and the temperatures drop quickly, sometimes all the way to freezing!

3 Some deserts are not hot, even during the day. Areas with low precipitation and high evaporation rates located in the extreme Northern Hemisphere are called tundras, a type of frozen desert. Because of the tundra’s extremely low temperature, any moisture that is present remains frozen.

4 Sandy deserts are the most familiar, probably because they are filmed and photographed so often for their natural beauty. Looking like giant, frozen ocean waves, sand dunes reach up to meet the brilliant blue sky. In fact, the dunes are not frozen at all. They are constantly moving and act more like the ocean than you might think.

5 Winds in the desert are very powerful because there is so little in the landscape to slow them down. The sand gets pushed around, just like water in the sea, and shifted and shaped into constantly changing wavelike forms. However, only about 20 percent of Earth’s deserts are made of sand. Most deserts consist of larger rocks like pebbles and stones. 6 The largest desert on Earth is the Sahara in northern Africa. Covering more than three-and-a-half million square miles, the whole United States could fit within this arid region. The Sahara is one of the driest places on Earth. It receives almost no rainfall during the year and has basically no surface water. However, there is water flowing underground that occasionally reaches the desert surface. An area of moisture and plant life within a dry desert is called an oasis. Although there are some natural oases, most of them are artificially created by irrigation or wells.

7 The Gobi is a major desert found in Asia. It sits on a plateau that stretches between two higher mountains. Even though part of the Gobi is as harsh as any desert, most of it is covered in a thin layer of bushes and grass that allows people to live there. The famous Venetian (v ’neSH n) traveler Marco Polo made his way across the Gobi in 1275, becoming the first explorer to describe this arid region to Europeans.

8 The largest desert in the United States is the Mojave Desert, which covers parts of California, Utah, Nevada, and Arizona. An area of the Mojave, called Death Valley, is the lowest and hottest point in North America. Despite its reputation for hot temperatures, the Mojave does get quite cold during the winter, regularly dropping to 20 to 30 degrees Fahrenheit, and it sometimes even snows there.

Spectrum Reading Grade 6

128

Write the words from the passage that have the meanings below.

1. the process by which liquid changes into vapor or gas

2. water that falls to Earth in the form of rain or snow

3. hills of sand that are pushed into shape by the wind

4. dry; having little rainfall

5. an area of flat land that is higher than the surrounding land

6. How much of Earth’s land surface do deserts cover?

7. Who was Marco Polo?

8. Why do some people compare sand dunes to ocean waves?

9. What is an oasis? What is the plural form of oasis?

Write T before the sentences that are true. Write F before the sentences that are false.

10. _____ Most of Earth’s deserts are made of sand.

11. _____ The Sahara receives almost no rainfall.

12. _____ The Mojave Desert is the largest American desert.

13. _____ The Gobi is located in northern Africa.

Spectrum Reading Grade 6

129