What are the three layers of a normal soil profile?

• A. Subsoil, bedrock, loam
• B. Topsoil, subsoil, and bedrock
• C. Topsoil, sand, bedrock
• D. Topsoil, subsoil, clay

Answer: (B)

In a soil profile, layers form from surface down as soil is weathered and organic matter accumulates. The top layer, or topsoil, is the uppermost mineral layer rich in organic matter and nutrients and supports most root activity. Beneath that sits the subsoil, which has less organic matter and more mineral content, often with accumulated clay and other materials leached from above. The bottom layer is bedrock, the solid rock that underlies the soil and from which the soil develops; over time, weathering of this material creates deeper soil horizons, but in this simplified view the three layers are topsoil, subsoil, and bedrock. Other options mix texture descriptors like loam, sand, or clay with layers, which are not distinct horizons of the profile.