Steady-state profiles of reacted fraction of albite () for different erosion rates (W) for the diffusion model. Local equilibrium regime: W< 0.001 m/ka; transition regime: W = 0.002 and 0.004 m/ka; kinetic regime: W = 0.0075 and 0.038 m/ka. The local equilibrium regime is the regime where porefluid is everywhere in equilibrium with albite and kaolinite, defining a sharp reaction front. In effect, the weathered zone contains no albite. In the transition regime, both albite and kaolinite occur in the weathered zone, but no albite occurs at the soil-air interface (). In the kinetic regime, both albite and kaolinite are found throughout the weathering regime, including at . We define the base of regolith by the reacted fraction of albite. For a reacted albite fraction = 0.2, the base of regolith, , is shown (regolith thickness ~ 0.06 m). The thickness of regolith at the point of change from transition to kinetic regimes, , is also shown.