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Notes Week 12 - Week 12 Geog 103 Weathering 10:57:00 AM...

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Week 12, Geog 103 19/11/2007 13:57:00 Weathering Denudation : any process that wears away or rearranges landforms Weathering vs. Erosion Weathering is the decay and disintegration of fresh rocks and minerals  through a complex process of interacting physical, chemical, and biological  processes. Erosion is the removal of the weathered material from one place to another.  Weathering and erosion operate simultaneously. Examples of Weathering: The Sphinx   limestone carved 5000-7000 B.C. Coupled chemical, physical and biological processes that define the Earth’s  weathering engine are driven by climate, anthropogenic, and tectonic forcing. Why do rocks weather? Rocks are not stable under many environmental conditions. Weathering alters the original lithology characteristics until what finally  remains of the former rock is an unconsolidated material consisting of: o New minerals created by the weathering o Minerals that resisted destruction (stable minerals) o Organic material added to the weathered zone Physical (Mechanical) Weathering    Disintegration Disintegration involves no chemical reactions.
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Produces smaller particles from larger ones Rock breaks down continuously as stress is exerted Preserves the chemical character of the rock. Chemical Weathering   Decomposition Mineral alteration or mineral decomposition – involves chemical reaction Involves change in chemical composition of minerals forming rock New minerals are created (secondary minerals, clays) Biological Weathering Biological Activity (people, animals and plants breakdown rocks) Roots of woody species exert expansive force as roots enlarge and lengthen Lichens contract during dry periods, tugging on rock surface. Regolith All three types of weathering processes produce a weathering  mantle  or  regolith  that constitute a weathering profile.
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