Which geographic concept explains why deserts form near 30 degrees north and south latitude?

• A. Coriolis effect
• B. Hadley cell (global atmospheric circulation)
• C. Ozone layer
• D. The water cycle

Answer: (B)

The main idea is how large-scale atmospheric circulation creates dry subtropical zones. In the Hadley cell, intense heating at the equator makes air rise and condense, producing heavy rainfall there. As that air moves toward higher latitudes, it cools and sinks around roughly 30 degrees north and south. The sinking air creates high pressure and dries the air, reducing humidity and cloud formation, which leads to desert conditions. This pattern explains why many deserts cluster near 30 degrees latitude on both sides of the globe, like the Sahara and the deserts of parts of Australia and the Americas. The other ideas don’t pinpoint why the dry belt sits at those latitudes: the Coriolis effect influences wind direction but isn’t the primary reason deserts form there; the ozone layer is unrelated to desert placement; and the water cycle is a broad process, not the specific mechanism that creates the subtropical desert belt.