- Cross - sectional soil layers from the surface of the soil down to the bedrock.
- O Horizon: Organic Material, surface layer of partially or completely undecomposed plant residue
- A Horizon: The uppermost layer of the soul commonly known as topsoil. This layer contains a large amount of decomposing organic material known as hummus, and most of the living organisms that dwell in the soil.
- B Horizon: Layer commonly known as the subsoil. Plant roots penetrate this area, but there is much less hummus and more inorganic content than the A Horizon.
- C Horizon: Bedrock, predominantly made from the parent material for soil. Large unbroken pieces of rock are weathered to create inorganic components of soil