Colluvium normally forms humps at the base of mountains or fan-shaped deposits similar in shape to alluvial fans that cover former ground surfaces. This process is an important phenomenon in the fields of archaeology and soil science.
Many colluvial soils tend to have a fragipan associated with them that are a brittle subsoil layer typically high in clay. One theory of fragipan formation is the smearing of soil during the colluvial process causing the clays to seal the surface between the moving portion of soil and the stationary soil on which it slides. Ancient sites can be preserved beneath colluvium if later changes in the landscape such as deforestation encourage a downward movement of material.