Physics professor Dr. Allen Hunt recently published his work, which sought to answer the important question of "why rates of soil development and rock weathering slow over time".
New research by Dr. Hunt, published in the Vadose Zone Journal, answers this question in terms of slowed solute transport, explaining the role of transport limitations on weathering. The depth of the chemically weathered layer on basalt surfaces was found using three known parameters: a fundamental length scale, equal to a pore size; a fundamental time scale (the time for water to flow through such a pore); and an exponent, which depends on the typical saturation conditions. The results of the modeling agreed with observations in sixteen studies performed on thousands of stones with ages from decades to a million years. The same analytical result using the same length scale, but a much smaller time scale appropriate for the much larger hydraulic conductivity of typical soils, gives the time dependent depths of 14 of the world’s soils, and rates of soil production at another 5 sites, under varied climatic conditions. Prediction of weathering rates for silicate minerals in consolidated and unconsolidated media is key to quantifying dominant global carbon fluxes on millennial scales and up, and in understanding past climate change and extinction events in the geologic record. Predicting soil production is important for understanding landscape evolution.
The article is available for download here.
