Idea for Use in the Classroom

Begin by having students open National Geographic MapMaker's Precipitation map. Direct students to focus on a single mountainous area, such as the Rocky Mountains of North America, the Himalayas of Asia, or the Andes of South America. Ask: How does precipitation vary on either side of the mountain range? Students should find that one side of the mountain range tends to receive more precipitation than the other. Prompt students to brainstorm possible reasons for these patterns.

To emphasize the effect of mountains on precipitation patterns, direct students to focus on the Atacama Desert, which exists along the western edge of northern Chile. Have students compare the amount of precipitation and rainfall in this area of Chile to the other side of the Andes in Bolivia and Argentina. Using this information, students can suggest the direction in which atmospheric wind patterns likely move across this region of South America and then perform research to determine if they are correct.

As a class, research the difference between leeward and windward sides of mountains and apply this information to the Andes. To extend learning, students can compare the precipitation and wind patterns of the Andes to those of the Cascade Mountains in the U.S. states of Oregon and Washington. Conclude by having students discuss how geographic factors can impact precipitation patterns and thus the availability of freshwater within surrounding ecosystems.