Fall22Quiz7

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University of Kansas *

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101

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Geology

Date

Dec 6, 2023

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docx

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2

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Geology 101, Fall 2022, Quiz 7 Due 11:59 pm on Monday, November 14 th . 1. In three or four sentences, describe the role that temperature, pressure, and fluids play in creating metamorphic rocks. How do geologists reconstruct the temperature and pressure at which a metamorphic rock was formed? (8 pts) Temperature plays a big role in its specific mineralogy, chemical composition, and texture by altering the existing crystal structures by breaking the chemical bonds formed. Pressure changes a rocks mineralogy, chemical composition, and texture through the process of placing stress on a rock. Fluids can change a rocks mineralogy and chemical composition by removing or adding chemical agents that are soluble in water. This has been experimented with differing pressures and temperatures on rocks to understand when changes or how these occurred. 2. Where in the world would you go to find blueschist, greenschist, and amphibolite facies metamorphism? Be specific: what plate tectonic setting would you go to, in what location in that setting would you look, and how deep would you need to go? (6 pts) Blueschist is found at subduction zones with depths of 20km-50km. Greenschist is found at convergent boundaries lying beneath mountains with depths of 5km-30km. Here the areas are of mid to high pressure and mid temperatures of 500 C. Amphibolite is found at convergent boundaries under mountains in areas of partial melting, within depths of 10km-40km in these areas of high temperatures and high pressure. 3. In three or four sentences and in your own words, describe the formation of a sedimentary rock from weathering, erosion, transportation, deposition, and burial, through diagenesis. Before doing your reading, you might have thought that these words were all synonymous—make sure your explanation distinguishes what each of these processes mean. (8 pts) Weathering of rocks are rocks that break into sediments by chemical or physical processes like thawing. Erosion dislodges the sediments, where then transportation of those sediments moves them to differing locations through things like wind, streams, and rain. These sediments settle out and dissolve with deposition. And the remaining sediments form layers on top of older ones through burial. Finally, the sediments then become lithified and create what we call sedimentary rocks or diagenesis.
4. Sediments are often transported by currents of air or water. How does the particle size that can be transported depend on the current strength/energy? (3 pts) When these currents slow the heavier particles settle to the bottom and rest there. If the current goes from really fast to very slow gravel will be on the bottom, then sand then mud on top. When it comes to particle size the bigger the current of water is the bigger the particle that can be transported. The stronger currents of 50cm/s can carry things like gravel. Moderate level currents that are 20-50cm/s can carry things like sand. The weakest of the currents which are less than 20cm/s can only carry really small particles.
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