Topography: Soil forming factor
Topography like parent materials is another passive control factor. The influence of topography is felt through the amount of exposure of a surface covered by parent materials to sunlight and the amount of surface and sub-surface drainage over and through the parent materials. Soils will be thin on steep slopes and thick over flat upland areas. Slope and aspect are two features of topography that affect soil formation. Slope refers to steepness (in degrees or percent) from horizontal and aspect is the direction the slope faces relative to the sun (compass direction). The steepness of the slope affects the amount of deposition or erosion of soil material.
Over gentle slopes where erosion is slow and percolation of water is good, soil formation is very favorable. Soils over flat areas may develop a thick layer of clay with the good accumulation of organic matter giving the soil dark color. In middle latitudes, the south-facing slopes exposed to sunlight have different conditions of vegetation and soils and the north facing slopes with cool, moist conditions have some other soils and vegetation.