Soil Horizons

C Horizon

Also called regolith; the layer beneath the B Horizon and above the R Horizon. It consists of slightly broken-up bedrock. Plant roots do not penetrate to this layer; very little organic material is found in this layer.

B Horizon

Also called the subsoil - this layer is beneath the E Horizon and above the C Horizon. It contains clay and mineral deposits (like iron, aluminum oxides, and calcium carbonate) that it receives from layers above it when mineralized water drips from the soil above.

A Horizon

The layer called topsoil; it is found below the O horizon and above the E horizon. Seeds germinate and plant roots grow in this dark-colored layer. It is made up of humus (decomposed organic matter) mixed with mineral particles.

O Horizon

The top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter.)

R Horizon

The unweathered rock (bedrock) layer that is beneath all the other layers.

E Horizon

This eluvation (leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon. It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips throughout he soil (in the process of eluvation).