There are three kinds of deserts; rocky deserts, stony deserts and sandy deserts. Sandy deserts are the least common kind of desert, but it is where you find sand dunes.

Sand dunes come in many patterns, each of which depends on how the wind is blowing. Many dunes have a steep slope and a gentle slope. The tops of many dunes are also curved.

Sometimes the sand piles up to make very tall star-shaped dunes (to the right in the picture below).

Although dunes are made from sand, and are dry and very hot in the daytime, plants grow and animals live here. Each kind of animal is specially adapted to survive. Plants like cacti grow in a desert, but there are many more kinds, too.