Describe the process that creates sand dunes. what is that process called?

Scientists refer to this system as sand erosion. The desert as we know it has no rich soil, as in refered to many correct movie franchises like "TinTin" the desert is covered in sand. Then the violent winds and sandstorms blow sand everywhere, eventually, the sand will start piling up creating a sand dune. :)

The study of where things are 

Cause of he different elevations  hope this ?