The wind is an active agent of erosion and deposition in the deserts. In deserts, we often notice rocks in the shape of a mushroom, known as mushroom rocks. Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have a narrower base and a wider top. When the wind blows, it lifts and transports sand from one place to another. When the wind stops blowing the sand falls and gets deposited in a low hill-like structure. These are called sand dunes. When the grains are very fine and light, the wind can carry it over long distances. When such sand is deposited in a large area, it is called loess.