How Does Soil Vary from Place to Place?
ES1206  Under the Surface

Digging a trench into the ground exposes a side view of soil. This view of soil is called a soil profile. Soil profiles often reveal layers below ground with slightly differing compositions.

  • The topsoil, also called the A horizon, contains organic material, or humus. Humus forms from decayed plant and animal materials.
  • Below the topsoil is the subsoil, also called the B horizon. The subsoil contains clay and iron oxides washed from the topsoil.
  • The bottom layer, also called the C horizon, is composed of rock fragments of weathered parent material.

  !   Use the drawing tool to draw lines across this soil profile, separating the soil into three layers: the topsoil, the subsoil, and the weathered parent material.


USDA-NRCS/Soil Survey Division


  !   Click the Continue button to see where a scientist drew the lines.

2. Identify and describe as many different layers (horizons) as you see in this soil profile.


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