What is substratum?
Substratum refers to a layer below the surface.
Substratum refers to a layer below the surface. The term is often used in soil science and it refers to the layer that lies below the surface layer and the subsoil (see images below). Soils typically have three major horizons: the surface horizon, the subsoil below that, and then the substratum
In the image above A) is the surface horizon; B) the subsoil and; C) the substratum