The denudation or destruction of the soil cover and their subsequent natural removal is termed as soil erosion. Human activities as well as natural forces cause denudation of the top soil. The soil nutrients are subsequently washed away by running water or blown away by wind. Human activities like deforestation, overgrazing, construction and mining as well as faulty methods of farming lead to soil erosion. Natural forces like wind, water and glacier can cause soil erosion. Surface runoff leads to formation of gullies, badlands and ravines by cutting out channels in the soil. Entire topsoil may be washed off under the impact of sheet erosion caused by large water flows down a slope. Loose soil may be blown away by wind easily. In hilly and mountainous areas the following measures can help to control soil erosion : (i) Contour ploughing or ploughing along the contour lines of a high land can decelerate flow of water down the slopes. (ii) Terrace cultivation or cutting of steps around the slopes to provide land for agriculture also checks downhill flow of water and controls soil erosion, e.g. as in Western and Central Himalayan region. (iii) Afforestation can help in soil conservation in hilly areas. In dry desert areas, planting of rows of trees known as shelter belts to check velocity of wind can control soil erosion. These shelter belts have contributed significantly to the stabilisation of sand dunes and checking the spread of desert in Western India