3. Free electives: Free electives are courses in addition to the Core Curriculum and major requirements sufficient to reach a minimum of 120 credit hours for graduation. Students may graduate with more but not less than 120 credit hours.
Evaporation rates regularly exceed rainfall rates. Sometimes rain starts falling and evaporates before reaching the ground. Rainfall is lowest on the Atacama Desert of Chile, where it averages less than 1.5 cm. Some years are even rainless. Inland Sahara also receives less than 1.5 cm a year. Rainfall in American deserts is higher  almost 28 cm a year.
There are three major hot and dry deserts in North America, all located in the Western United States and Northern Mexico. These are: 1  The Chihuahuan Desert â the largest desert in North America, located in the Southwestern United States and Northern Mexico - (140,000 square miles (360,000 km 2)).2  The Sonoran Desert â a desert located in the Southwestern United States and Northwest Mexico.here are three major hot and dry deserts in North America, all located in the Western United States and Northern Mexico. These are: 1  The Chihuahuan Desert â the largest desert in North America, located in the Southwestern United States and Northern Mexico - (140,000 square miles (360,000 km 2)).