Soil generally consists of visually and texturally
distinct layers, which can be summarized as follows from top to bottom:
O) Organic
matter: Litter layer of plant residues in relatively undecomposed form.
A) Surface soil:
Layer of mineral soil with most organic matter accumulation and soil life.
This layer eluviates (is depleted of) iron, clay, aluminum, organic compounds,
and other soluble constituents. When eluviation is pronounced, a lighter
colored "E" subsurface soil horizon is apparent at the base of the
"A" horizon. A-horizons may also be the result of a combination of
soil bioturbation
and surface processes that winnow fine particles from biologically mounded topsoil.
In this case, the A-horizon is regarded as a "biomantle".
B) Subsoil: Layer of
alteration below an "E" or "A" horizon. This layer
accumulates iron, clay, aluminum and organic compounds, a process referred to
as illuviation.
C) Substratum: Layer
of unconsolidated soil parent material. This layer may accumulate the more
soluble compounds that bypass the "B" horizon.
ACKNOWLEDGEMENT: “Borrowed” from Wikipedia