Loess hills and sand dunes formations are created by wind deposition
Step-by-step explanation:
Sand dune begins with an obstruction, such as a rock. The obstruction makes the wind to relax down. The wind then leaves some of its sand. As added sand is dropped, the hill gets bigger. The hill becomes the obstruction that reduces the wind and causes it to leave its sand. Once a sand dune designs, it may slowly transfer over the land. The wind pushes fragments of sand up the smoothly tilted side of the hill. This is caused by saltation.
When the wind leaves minute particles of silt and clay, it creates heaps called loess. Loess sediments build vertical cliffs. Loess can convert a thick, rich soil. So loess sediments are practiced for agriculture in many parts of the world. Although ancient geologists thought loess was either deposited by a river or formed in a lake, now we know that loess was eolian (deposited by the wind).