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23 Cards in this Set
- Front
- Back
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What is metamorphism?
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Transformation of rocks into another rock from heat and pressure
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What happens during metamorphism?
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Rocks undergo extreme heat and pressure causing a change but they do not melt (melting is for igneous rocks)
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What are the three elements of metamorphism?
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heat, pressure or stress, chemically active fluids
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what is the single most important factor in metamorphism?
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Heat
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Does folding commonly accompany regional metamorphism? What does this tell us about the pressure/stress conditions operating during metamorphism?
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yes, it tells us that there was high pressure/stress in these areas
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What happens to minerals and textures of rocks due to metamorphism?
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Minerals grow close to stability at the high temp and press.
Texture changes due to applied stress |
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where does metamorphism tend to occur?
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deep in crust where there is high pressure, high temperature, usually > 12 miles in crust)
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what is metamorphic grade? How does it vary?
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In varies from low to high grade
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What does high grade metamorphism do to the original mineralogy and texture of a rock?
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The higher the grade the larger the minerals grow
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What are the three driving force of metamorphism?
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Internal heat of earth, lithospheric pressure, horizontal pressures as rocks become deformed--tectonic forces)
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Why is heat so important to metamorphism?
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because it drive chemicals to react and that changes minerals
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How is pressure/stress important in metamorphism?
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Pressure forms the shape of the rock
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What are confining pressure and directed pressure? How do they relate to metamorphism?
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They relate because the pressure forms the rock
Confining Pressure: pressure exerted in all directions Direct pressure: Differentials stress on objects |
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How do fluids produce changes in metamorphism?
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extremely hot fluids under pressure dissolve ions such as NA, Silica, K, Metals
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What are the two major types of metamorphism and what are their characteristics
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Contact metamorphism:Igneous intrusion causes high temp that breaks host rocks
regional Metamorphism: Occurs during mountain building associated with subduction of continent collisions |
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How does contact metamorphism occurs? What are the pressure temperature conditions?
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Igneous intrusion causes high temperature that break host rocks. The conditions are high temperature and low pressure.
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How does regional metamorphism occur? What are pressure temperature conditions?
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Occurs during mountain building associated with subduction of continent collisions. The conditions are high temperature and high pressure.
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What sort of forces or stress accompany regional metamorphism?
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there is high temperature and high pressure. Accompanied by large scale folding and faulting.
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What is foliation?
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is flat or wavy parallel textures produced by stress caused by regional metamorphism
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What is index minerals?
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The appearance of certain metamorphic minerals that tell us how interior metamorphism was... ie "grade"
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What are blueschist metamorphic rocks and where (under what conditions) do they form?
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Blueschist: Metamorphic rock with blue color. They form in subduction zones
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In what sort of plate tectonic settings does regional metamorphism occur (continent-continent collisions and subduction zones)
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convergent plate boundaies
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What is a shield area, where do they occur, and what are they thought to represent?
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A shield area
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