Several causes can be attributed to deserts, including the Earth's air circulation pattern, the rain shadow effect, the distance from the ocean and the proximity of cold ocean currents. Some common deserts in the United States include the Colorado Plateau that stretches through Colorado, Utah, Arizona and New Mexico, and the Basin and Range in Nevada, Utah, California and Arizona.
The Earth's air circulation pattern is one cause of a desert that can be explained by the fact that warm air holds more moisture than cold air. This results in the evaporation of water and the formation of deserts. When hot air rises it cools as it approaches a mountain. It is harder to hold water, and the side of the mountain approached by the air gets rain. The opposite side of the mountain receives dry air, and that side is what's referred to as the desert. This is what is known as the rain shadow effect. Land that is further from the ocean is where air absorbs most of the water. This is why the distance from the ocean affects the formation of a desert. Cold ocean waters warm when passing over a continent.
One human activity that is strongly linked to the process of desertification is deforestation.