Terrain cross-section of the Americas: windward and leeward slopes
GeographyRegions & CountriesAges 12–13
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Regions & Countries
Choose a cross-section through North America (about 40°N) or South America (about 20°S) to see three north–south belts of relief: high mountains in the west (the Cordillera, the Andes), plains in the middle, and older mountains or plateaus in the east. Press Run to send a moist air mass along the wind's path: it cools and drops rain as it climbs the windward slope, then dries out and warms as it descends the leeward slope, creating a desert right next to a wet region. The rainfall bars below the cross-section show the relative rainfall at each point.
Lesson: Physical geography of North America and Middle/South America: relief and climate variation
What it shows
When moving air meets a mountain range it is forced to rise, and in this model it cools by about 0.6 °C for every 100 m of height. Water vapor condenses and falls as rain on the windward slope; beyond the crest the air sinks, warms and dries out, leaving a rain shadow on the leeward side. The two cross-sections show the relief belts of the Americas: young, high mountains in the west, broad plains in the center and older, lower highlands in the east. Together they explain why deserts such as the Great Basin and the Atacama lie close to very wet regions.
How to use
Choose a Cross-section and name the relief belts from west to east, then press Run and follow the air mass as its altitude, temperature and remaining humidity update. Compare the rainfall bars on the windward and leeward slopes. Use Switch wind to reverse the Wind direction, and lower the Humidity of the air mass at the coast to see how a drier air mass changes the pattern of rainfall.
Parameters you can change
- Cross-section North America, about 40°N, South America, about 20°S
- Wind direction West to east (prevailing westerlies), East to west (trade winds)
- Humidity of the air mass at the coast 30–100 %
- Air mass speed 0.3–3 ×
Questions to explore
- What are the three relief belts along the North America cross-section, in order from west to east?
- Why is the leeward slope of a mountain range usually drier and warmer than the windward slope?
- When the wind blows from east to west, which slope of the Andes becomes the windward slope?
