If the soil is bare and exposed and sloping downhill, a rainfall will likely take soil downhill, perhaps to a creek, where it will add silt and pollutants to the water. If the soil is bare and exposed, a wind can blow away loose particles from the top. read more
If wind is dusty, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid (air or water) and being transported from one place to another. This transported material is called sediment. read more