GEOG-120 Lecture Notes - Lecture 27: Parent Material, Humus, Interaction
22 Dec 2020
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Agriculture and the transformation of biophysical systems. Physical/mechanical weathering breaks rocks down without triggering a chemical change in the parent material (temperature, wind, rain and ice) Chemical weathering results when water or other substances chemically interact with parent material (when groundwater is unusually acidic) Biological weathering occurs when living things break down parent material by physical or chemical means: biological activity further contributes to soil formation through decomposition, deposition, and accumulation of organic matter: As plants, animal and microbes die or deposit waste, this material is incorporated into the substrate, mixing with minerals. In decomposition, complex organic molecules are broken down into simpler ones, including those that plants can take up through roots. Partial decomposition of organic matter creates humus, dark, spongy mass of material made up of complex organic compounds; high humus content hold moisture well. Peat is soil dominated by partially decayed organic material.
