Answer:
The movement of Loess
Loess are deposits of fine particles of silt and clay formed by the wind. It is known to be a deposits form vertical cliffs which is often forms a thick, rich soil.
The movement of sand forms the Sand Dunes.
A sand dune is formed when an obstacle (rock) slows down the wind causing some sand accumulation by the wind. The dune increases in size, slowly occupying the land as more sand is deposited by saltation (deposit of more grains of sand along the gentle slope).
