ENV-1010 Lecture Notes - Lecture 14: Weathering, Pedogenesis, Topsoil
13 Sep 2016
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Weathering: mechanical (physical)- breakdown into smaller pieces with little or no chemical change. Ice and frost wedging h2o freezes, expands and pops rock apart. Unloading removal of weight causes rock to expand and crack. Wind sandblasting: chemical- breakdown by a chemical change. Hydrolysis mineral reacts with water and dissolves or partly dissolves. Acidation rock reacts with acid in rain (carbonic, sulfuric, nitric, hydrochloric) Smaller grains = more surface area = faster weathering: fractures. More cracks = more surface area = faster weathering: composition. Hard to weather = forms more soil. Quartz is most common component of soils, tough to break down. Soil: soil is a mixture of rocks and minerals, organic matter, water, air, and organisms. A slow process; hundreds to thousands of years. General soil profile: soil profile- most soils occur in a series of layers or zones. A horizon- sand and humus (decomposed organics; some material leached to b horizon)
