Dunes are hills of sand which are formed by the action of winds which is an agent of weathering. Sand dunes usually formed along the beach or in a desert. Sand dunes form when the wind blows, they carry particles of sand before they drop to the ground. As they roll and bounce on the ground, sand particles create small, wave-shaped ripples of sand. These ripples can build up into larger structures.
Dunes can grow very high say up to 4000 feet and be many miles long. Dunes can be various shapes such as crescents, stars, or just repeated lines.
