4. Continental arc volcanism and regional chemical weathering
It is natural now to explore the effects of uplift and physical weathering on regional chemical weathering. We assume that chemical weathering occurs primarily when the rock is in residence in the soil ZJ 43 overlying the bedrock, where soil is distinguished from bedrock in having higher porosity owing to chemical weathering and bioturbation. Soil formation processes occur on timescales much faster and length scales much shorter than secular changes in orogenic activity, so the details of soil formation on overall erosion rates was ignored in Section 2. However, as we show below, chemical weathering fluxes are strongly influenced by soil residence time because it dictates what fraction of the physically eroded material is chemically weathered (dissolved).
Fig. 9. A. Cartoon illustrating the soil formation model. Thickness of soil mantle on a mountain is controlled by bedrock to soil conversion P and erosion E. Rate of bedrock to soil conversion is assumed to decay exponentially with depth over a characteristic decay length D. B. Time for a soil mantle to reach steady-state thickness as a function of erosion rate. C. For a steady-state soil mantle profile, residence time of material in the soil mantle as a function of erosion rate.Figure optionsDownload full-size imageDownload high-quality image (371 K)Download as PowerPoint slide
It is natural now to explore the effects of uplift and physical weathering on regional chemical weathering. We assume that chemical weathering occurs primarily when the rock is in residence in the soil ZJ 43 overlying the bedrock, where soil is distinguished from bedrock in having higher porosity owing to chemical weathering and bioturbation. Soil formation processes occur on timescales much faster and length scales much shorter than secular changes in orogenic activity, so the details of soil formation on overall erosion rates was ignored in Section 2. However, as we show below, chemical weathering fluxes are strongly influenced by soil residence time because it dictates what fraction of the physically eroded material is chemically weathered (dissolved).
Fig. 9. A. Cartoon illustrating the soil formation model. Thickness of soil mantle on a mountain is controlled by bedrock to soil conversion P and erosion E. Rate of bedrock to soil conversion is assumed to decay exponentially with depth over a characteristic decay length D. B. Time for a soil mantle to reach steady-state thickness as a function of erosion rate. C. For a steady-state soil mantle profile, residence time of material in the soil mantle as a function of erosion rate.Figure optionsDownload full-size imageDownload high-quality image (371 K)Download as PowerPoint slide