Soil is comprised of three layers. First you find topsoil. This is the ground layer we walk upon, commonly referred to as 'dirt'. It is nutrient rich due to the decaying plant and animal matter, called 'humus', within. Beneath the topsoil we find the lighter colored subsoil.
Subsoil is the middle layer that contains large rocks alongside minerals washed out of the topsoil.
The final layer is the substratum, this is the deepest layer where rocks weather to form new subsoil. Beneath the substratum is the solid, hard bedrock, untouched by weather, plant or animal. Illinois State Goal Standard Learning Benchmarks 12 B 1a. Describe and compare characteristics of living things in relationship to their environment. Identify components and describe diverse features of the Earth's land, water and atmospheric systems.