What causes deserts to form?

Deserts form due to a combination of factors, including low precipitation, high evaporation rates, and specific atmospheric conditions. Many deserts, such as the Sahara, are located in regions where dry air descends from the Hadley Cell circulation, preventing rain. Others, like the Atacama Desert, form in rain shadows caused by mountains that block moist air. Coastal deserts, such as the Namib, are influenced by cold ocean currents that reduce humidity. These environmental factors create arid landscapes with sparse vegetation, adapted to survive in extreme conditions.