GEOL 1010 Lecture 8: SEDIMENTARY ROCKS
24 Sep 2016
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Document Summary
Erosion / weathering: weathering -- the disintegration or decomposition of a rock. In situ -- does not include movement, in place. Mechanical (physical): breaks the rock into smaller chunks without altering its minerals. Minerals that have cleavage planes are more likely to be mechanically weathered. Also from changes in pressure and temperature, like in yosemite. Chemical: changes the actual mineral composition of a rock. Ex: granite to a mud, from a long period time. Quartz grains are weathered, turned to sand grains, etc. Oxidation is also a chemical weathering; the rust color in sandstones comes from oxidation. Role of water is often important -- polar molecules can cause other materials to break up and dissolve. Mafic minerals are more susceptible to chemical weathering than are silica-rich minerals. Quartz is resistant to chemical weather, forming sand, but all other common silicate minerals break down chemically to form clay materials. Through weathering process, rocks are turned into soil.
