Subsoil

It is the layer of soil under the topsoil on the surface of the ground. The subsoil may include substances such as clay and has only been partly broken down by air, sunlight, water etc., to create true soil. Below the subsoil is the substratum, which can be residual bedrock, sediments, or Aeolian deposits, largely unchanged by soil-forming factors active in the subsoil? It contains partially weathered particles.