Fine soil components are deposited in the subsoil by gravitational water during which process?

Illuviation is the process described in the question, where fine soil components, such as clay and minerals, are deposited in the subsoil. This occurs as water moves downward through the soil layers, often carrying dissolved or suspended materials with it. When gravitational water percolates through the soil profile, it can leach out soluble substances from the upper layers and deposit them in the lower horizons, specifically the subsoil. This accumulation of materials can enhance the nutrient content and alter the characteristics of the subsoil.

In contrast, leaching refers to the process of soluble substances being washed out from the soil and into the groundwater or lower soil layers, rather than being deposited into the subsoil. Percolation is related to the movement of water through the soil but does not specifically address the depositing of materials. Erosion involves the removal of soil and rock from one location to another, often due to wind or water, rather than the deposition of soil components in the subsoil. Therefore, illuviation specifically highlights the accumulation aspect that is central to the process described in the question.