Earth Sciences 1083F/G Lecture Notes - Lecture 9: Metasomatism, Chert, Phyllite
12 Sep 2016
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Document Summary
Sedimentary rocks are formed by the accumulation and hardening of sediment. When exposed at earth"s surface, rocks are broken down by processes of weathering (due to dissolution and physical breakdown). Mechanical weathering: physical breakup or disintegration of rocks without changes in their composition. In areas where the degree of chemical weathering is very low (e. g. in cold, dry, regions of the canadian arctic), clastic sediment can consist almost entirely of small fragments of rock with no change in mineral makeup. Biologically aided weathering: living things can also influence weathering. For example, plant roots can widen cracks in the rock. Also, the decomposition of plant matter can produce organic acids that aid in chemical weathering. Chemical weathering: breakdown or decomposition of minerals due to chemical reactions of minerals with water or gases in the air (involves chemical change): some minerals are more susceptible to weathering than others.
