Subsoil

Subsoil, or substrata, is the layer of soil under the topsoil on the surface of the ground. The subsoil may include substances such as clay and/or sand that has only been partially broken down by air, sunlight, water, wind etc., to produce true soil. Below the subsoil is the substratum, which can be residual bedrock, sediments, or aeolian deposits, largely unaffected by soil-forming factors active in the subsoil. It contains partially weathered particles. It is usually a lighter shade of brown or yellow. It contains the deeper roots of large plants, like trees, but otherwise not much lives here.