In the broad sense, desert and barren sandy land are the same, both being places of dry climate, low rainfall, high evaporation and poor vegetation. In the narrow sense, however, desert is one particular type of barren sandy land whose surface is covered with unconsolidated deposits consisting of small mineral granules, like quartz. These substances are carried by the wind to form sand dunes with various profiles. With interdunal lands in between, the undulating dunes link together to form a great sea of sand. The Alxa Desert is made up of three deserts, Badain Jaran, Tengger and Ulan Buh Desert.