Soil erosion is a natural process; it is part of the constant recycling of Earth materials that we call the rock cycle. Once soil forms erosional forces, especially water and wind, move soil components from one place to another. Every time it rains, raindrops strike the land with surprising force(Figure 4.19). Each drop acts like a tiny bomb, blasting movable soil particles out of their positions in the soil mass. Then, water flowing across the surface carries away the dislodged soil particles. Because the soil is moved by thin sheets of water, this process is termed sheet erosion.