Weathering - refers to the chemical and physical breakdown of rocks. Weathering occurs because minerals are not at thermodynamic equilibrium with the environment. Weathering is approximately the same as pedogenesis or soil formation. Pedochemical weathering occurs within the solum. Geochemical weathering can occur at depths below that of soil formation.
Some researchers make a distinction between pedochemical and geochemical weathering.
However, the processes are generally similar, and we will not attempt to separate these processes in this course. It is often more important in arid climates where there is insufficient water for chemical weathering. See Weathering, Mass Wasting, and Erosion. Physical weathering can reduce rock material to no smaller than silt-sized particles. To produce clay-sized particles, chemical weathering is necessary.