GSCI 1052 Lecture Notes - Lecture 7: Chert, Siltstone, Petrified Wood
23 Jan 2018
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Document Summary
Salt- occurs on coasts, especially in arid regions where sea spray evaporates quickly: thermal expansion- heating causes a rock to expand, cooling causes contraction. This is typical of the weathering of feldspars into clays: hydration- water added to mineral crystals. Some clays expand when hydrated, weakening rocks: oxidation- mineral"s positive ions react to o2 to form an oxide. Iron oxides are major components of some sedimentary rocks. The results of weathering are sediments- loose grains of rocks, minerals and biological materials as well as chemical residues that will precipitate as mineral crystals. There are three types: clastic- broken fragments of preexisting rocks, biogenic- residues of once living organism. These can be clastic or chemical: chemical precipitates- minerals deposited when water evaporates. Sediments are transported by gravity, water, wind, or ice to their place of deposition (this is known as erosion) Weathering is the break down of rocks while erosion is the transportation of rocks from point a to point b.
