Weathering

weathering, breakdown of rock, disintegration, decomposition

physical or mechanical weathering: cracks, pressure release, exfoliation, sheet joints, frost wedging, biological processes, mineral growth, thermal expansion (heat and fire), abrasion, rounding,

chemical weathering: oxidation of iron, acidic water, hydrolysis, carbonic acid,

• calcite (limestone) dissolves into solution,
• feldspar >>>> clay minerals & material in solution,
• Fe-Mg minerals >>>> Fe-oxides & clay minerals & material in solution
• quartz is relatively stable

Soils

weathered, unconsolidated, residual soil, transported soil

soil horizons: not always equally well developed

• O, organic material on surface (humus),
• A, zone of leaching, removal of soluble material (coffee)
• B, zone of accumulation, evaporation leaves minerals,
• C, transition zone, partially weathered bedrock,
• bedrock

arid, excessive evaporation, large B horizon, pedocal, caliche, accumulation,

humid, tropics, pedalfer, extreme leaching, laterite, infertile, rain forest denudation

What are the differences between mechanical weathering and chemical weathering? Describe four mechanical weathering processes. How are the following minerals affected by chemical weathering: quartz, calcite, feldspar, olivine?

What natural substances contribute to formation of acid (for chemical weathering)? What substances do humans create which contribute to formation of acid? What minerals are affected by acidic water?

List major minerals in terms of their stability at the Earth's surface. What are the products of the chemical weathering of calcite, quartz, feldspar, Fe-Mg minerals?

Describe the three soil horizons. How does climate affect them? Give examples. Why can tropical soils support rain forests, but not be very fertile for agriculture? How does irrigation promote the buildup of minerals and salts in the soil of arid regions?
 
 

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