Soil profileA cross section of soil exposed by digging is called the soil profile. The weathering of soil produces layers known as soil horizons. First is the Litter / Humus layer (labeled O horizon [for organic] below). The topsoil or A horizon is usually rich in dark-colored organic remains called humus. The subsoil or B horizon contains minerals that have been transported deeper by groundwater. Most of the clay in soil has also been washed down to this layer. The partially weathered bedrock or C horizon is composed of broken up bedrock on top of the solid bedrock (parent material).
Under horizon C is the Bedrock