Lecture 7 Notes

Lecture 7 Notes - Lake Bonneville was a prehistoric lake...

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Lake Bonneville was a prehistoric lake that existed during the ice ages. It covered a large portion of Utah. Red Rock Pass used to act as a natural dam, holding the lake in. 16,800 years ago, the water level of Lake Bonneville rose above this natural dam. As waters flowed over the rocks at Red Rock Pass, it eroded the dam, causing a gigantic, catastrophic flood which emptied much of the lake into Idaho. The flood waters causes catastrophic erosion of the Snake river area. The great Salt Lake is all that is left of Lake Bonneville. The Bonneville salt flat is part the ancient lake floor of Lake Bonneville.
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Basalt Flows of the Snake River Plain Twin Falls, Idaho
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Basalt Flows of the Snake River Plain [Evel Knieval Jump Site] Twin Falls, Idaho
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Evel Knieval Jump Site tried to “jump” this canyon on a rocket cycle. 1974
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It didn’t work out too well!
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There are 2 types of sediments: Clastic sediments : rock fragments and clay formed by the weathering of pre-existing rock. Chemical or biochemical sediments (we’ll just say chemical): new chemical substances caused by the precipitation of dissolved ions or compounds. Weathering breaks down rocks into sediments Erosion transports sediments Sediments are fragments of rock, clay, or chemically precipitated minerals. Review
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Close to the source (sediments deposited near mountains) Angular sediments More variety in minerals All different sizes of sediments Arkose Review
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Far from the source (sediments deposited far away from mountains) Rounded sediments Less variety in minerals (mostly quartz and clay) Well sorted sediments Review
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Chemical Sediments Examples: Halite (salt), gypsum, sea shells
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Chemical sediments are transported a little differently Chemical weathering breaks rocks down into dissolved compounds and ions These dissolved components travel easily down rivers Eventually, these dissolved components empty into a lake or ocean As the concentration of dissolved components increases, new minerals are precipitated. Remember this example: Feldspar + Water = Kaolinite + dissolved silica (SiO 2 ) + dissolved Potassium Ions (K + )
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The oceans are salty because all of the rivers dump the dissolved ions and compounds from chemical weathering into them.
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Chemical sediments are typically precipitated in the following 2 ways: 1. Heavy evaporation – creates deposits of halite and gypsum When water evaporates, it leaves the dissolved ions and compounds behind. This causes the concentration of the dissolved ions and compounds to
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This note was uploaded on 03/03/2010 for the course GEOLOGY glg 321 taught by Professor Na during the Spring '10 term at ASU.

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Lecture 7 Notes - Lake Bonneville was a prehistoric lake...

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