The nature of soils varies according
to geographical location, climate, etc. However, the topsoil will
often be dark brown or black in colour (though not in very arid
or dry areas), and is made up of rock material that has been chemically
and physically broken down and changed, and mixed with organic
materials such as dead plants, particularly roots of them. Furthermore,
it will generally be full of plant and animal life.
The subsoil also consists of altered rock material, but contains
much less plant life (mainly roots) and living creatures. However,
minerals can be broken down, and nutrients released from this layer
for use by roots of plants.
Finally, the parent material is located at the very bottom, usually
below half a metre and consists mostly of unaltered rock or glacial
deposits, the matter from which the soil is developed.