Figure 21.12 Weathering rates in 21 Canadian watersheds in Quebec. When researchers quantified the combined inputs and outputs of calcium, magnesium, potassium, and sodium, they found that the rates of weathering differed a great deal across the landscape.

After D. Houle et al., Soil weathering rates in 21 catchments of the Canadian Shield, Hydrology and Earth System Sciences 16 (2012): 685–607.