Deserts: The World's Dry Places

A desert is any area that receives very little rainfall — fewer than 25 centimetres of rain per year. Deserts cover about one third of the Earth's land surface, making them the most common type of landscape. The word 'desert' comes from a word meaning 'abandoned' or 'empty', because so few plants and people can survive in such dry places.

Many people imagine every desert as endless golden sand, but this is a common mistake. In fact, only about a fifth of the world's deserts are sandy. Most are covered in bare rock, gravel, or pebbles, and some, like the cold deserts, are covered in ice. What truly makes a place a desert is the lack of rain, not the sand.

Hot deserts can be scorching during the day but bitterly cold at night. Because there are few clouds or plants to hold the warmth, the heat escapes quickly once the Sun sets, and temperatures can fall close to freezing. Sand dunes in hot deserts are shaped by wind blowing sand into huge, rippling hills that slowly move across the land over the years.