D. Natural desert formation 1. Areas around the equator have moist air a. Results in high rain amounts 2. Now dry air moves north resulting in drier areas a. These areas are usually deserts b. Deserts will fall just above the equator

a. Other deserts tend to be behind mountains b. Most of the U.S. deserts c. Caused b/c the moisture is sucked up through the soil by evaporation 3. Another factor is what is called a rain shadow

E. Desertification 1. Process that changes semiarid lands to deserts from human activity is desertification a. Semiarid regions are delicate b. Usually through livestock farming 2. Occurs from hooves, overgrazing, and logging

a. Plants hold topsoil and moisture b. When they are gone sun is just reflected causing new wind patterns and temperatures to change 3. Has occurred everywhere but Antarctica a. Big problem; area the size of Maine per year b. U.S., S. America, Australia, China, and Africa are the biggest.