Answer: erosion
Erosion is the process of removal and displacement of surface soil particles by the effect of wind, water or chemical agent. The sediments due to the effect of these agents gets displaced to locations other than the one where their parent rock or soil originated. A sand dune can be defined as the accumulation of grained sized sand into the shape of ridge by the effect of wind under the influence of gravitational force exerted by the earth. Dunes are formed when the loose sand is blown by wind. Therefore, sand dune is the erosion of sand by wind. Sand dunes are formed in deserts, beaches, barren fields and semiarid regions.
