Deserts generally receive less than 10 inches of precipitation a year, while semiarid regions receive on average between 10 and 20 inches a year. These regions make up about 1/3 of the earth's surface. Deserts are moving all the time due to continental drift and growing mountain ranges. Deserts are found between 15 and 30 degrees north and south of the equator.

Deserts vary in age. The Sahara in northern Africa is 65 million years old and the Kalahari Desert, also in Africa, is much older than that! The Sonoran Desert in North America is a baby by comparison at about 10,000 years old. Due to the extreme heat and dryness (aridity), the desert ecosystem is extremely fragile and efforts are underway to protect these desolate wonders of nature.

Objectives

• Students will be introduced to deserts in a number of environments, including Africa, North and South America, and Australia.
• Students will learn some basic principles about deserts.
• Students will be taken to various Web sites where they can research various types of information about deserts.

Concepts

1. How are deserts formed?
2. What percentage of the earth is classified as desert?
3. What poisonous animals are found in the desert?
4. Are deserts expanding or shrinking?
5. Where in the world is the largest desert?
6. Are there different types of deserts?

Terms To Learn