Which best describes the process of eluviation?

Eluviation is characterized by the leaching or removal of minerals and nutrients from the upper layers of soil, particularly the topsoil, as water percolates through the soil profile. This process typically occurs in the A horizon, where organic matter and minerals are washed away, leading to a loss of fertility in that layer. The leaching can result in the accumulation of materials in lower horizons, which contrasts with the concept of accumulation in topsoil.

Other processes mentioned in the options highlight different soil dynamics that do not align with the definition of eluviation. For example, the build-up of nutrients in topsoil pertains to the process of illuviation, which involves the accumulation of material in lower soil layers rather than the removal from the top. Layering of different soil types relates to soil stratification, and the formation of new soil refers to pedogenesis, which involves biological, chemical, and physical changes in the soil profile over time. Thus, understanding eluviation as the leaching process clarifies its role in nutrient dynamics and soil health.