Why do Sand Dunes move across Deserts ?

Only about one- fifth of hot deserts are covered with sand. Strong winds often blow in deserts. Because deserts are dry and so not have any vegetation, loose sand can be driven along by wind. The constant movement of sand from one side of a dune to the other moves the dune .

Deserts are probably getting bigger because there is less rain. Also, strong winds move sand further out cover the neighboring land. Bad farming has also led to the soil being worn away, creating deserts.