Which horizon is best described as subsoil, a lighter layer below the topsoil with mostly minerals and little organic matter?

• A. O Horizon
• B. C Horizon
• C. B Horizon
• D. A Horizon

Answer: (C)

The layer described is the C horizon. In soil profiles, the topmost layer (A horizon) is rich in organic matter and forms the fertile surface. Below that, the B horizon is the subsoil where minerals from above accumulate and where some leaching has occurred, often with less organic material than the topsoil. The C horizon lies beneath these processed layers and consists mainly of weathered parent material with little alteration and little organic matter, so it is mineral-dominated and lighter in color. This makes it the best match for a lighter, mostly mineral layer just below the topsoil with little organic content.