What is the term for the layer of soil that is most susceptible to erosion?

The most susceptible layer of soil to erosion is the topsoil. This layer is typically rich in organic matter, nutrients, and microorganisms, making it critical for plant growth. Due to its loose texture and high organic content, topsoil is easily washed away by rainfall and surface runoff. When vegetation cover is removed, the protective layer provided by plants is lost, leaving the topsoil vulnerable to erosion.

In contrast, other soil layers like subsoil and bedrock are less prone to erosion. Subsoil, which lies beneath the topsoil, contains larger clumps of soil and is more compacted, thus providing a greater resistance to erosive forces. Bedrock, being the solid rock layer beneath the soil, is even more stable and impervious to erosion compared to the topsoil. Clay soils, while having some erosion protection due to their fine particles, can also be prone to erosion under certain conditions, but they are not as susceptible as the topsoil.

Thus, the characterization of topsoil as the layer most vulnerable to erosion highlights the importance of soil conservation practices to protect this essential resource.