Exam 2 Chapter 8 – Flashcards
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Which of the following factors describes the conditions at a zone where contact metamorphism is occurring?
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high temperature, low pressure
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What is a metamorphic aureole?
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a ring of metamorphic rocks adjacent to an igneous intrusion
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How is quartz sandstone metamorphosed into quartzite during contact metamorphism?
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Sand grains are fused together because of high temperatures
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Which of the following best describes confining pressure and the location in which it occurs?
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moderate pressures at shallow depths
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Which of the following metamorphic rocks could have a parent rock (protolith) of shale?
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Slate, Phyllite, Gneiss, Schist
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Which of the following is associated with the metamorphic rock phyllite?
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intermediate-grade metamorphism
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Which of the following factors describe the conditions at a zone where low-grade regional metamorphism is occurring?
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Low pressure, low temperature
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Which of the following describes the orientation of the long axes of rocks and mineral grains in relationship to the stress applied?
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-Mineral grains are oriented parallel to the direction of the weakest stress applied.
-The long axis of a rock is parallel to the direction of the weakest stress applied.
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Metamorphism involves the transformation of pre-existing rocks by _____.
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heat and pressure
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Which of the following best describes the difference between differential stress and confining pressure?
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In differential stress, the stresses on the sides are greater than the force of gravity. Stresses are the same on all sides for confining pressure.
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How are metamorphic rocks formed?
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Preexisting rock is altered through heat and pressure.
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Do metamorphic rocks look like the preexisting rock from which they form?
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sometimes, but not always
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What is foliation?
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banding in metamorphic rocks that results from the reorientation of minerals
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How will foliation in continental metamorphic rocks formed during subduction be oriented?
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perpendicular to the direction of plate movement
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What would you call a granite that has undergone metamorphism and now exhibits foliation?
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Gneiss
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What role does hot ion-rich water play in the process of metamorphism?
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Water migrates into host rock carrying ions to stable minerals in order to facilitate growth of new metamorphic minerals.
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By what process did the gabbro turn into amphibolite?
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The gabbro was heated to 500 °C and buried a few miles below the Earth's surface.
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What is a mantle plume?
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hot mantle rock rising from deep within the Earth
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What kind of metamorphic texture results in the segregation of light and dark mineral bands?
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gneissic texture
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Why are garnets used in sandpaper?
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Garnets have a value of 8 or 9 on the Mohs Hardness Scale, making them very abrasive.
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What kinds of rocks can become metamorphic rocks? Choose all that apply.
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Igneous rocks, sedimentary rocks, metamorphic rocks.
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What platy, parallel mineral grains are the most visual aspect of foliated metamorphic rocks?
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Micas
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Which of the following rock types form during the highest grade of regional metamorphism?
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Schist
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During metamorphism, what is the major effect of chemically active fluids?
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They aid in the movement of dissolved silicate constituents and facilitate growth of the mineral grains.
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What type of metamorphic facies associated with the subduction of oceanic crust and sediments forms at very high pressure but moderately low temperature?
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Blueschist
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What major change occurs during metamorphism of limestone to marble?
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Calcite grains increase in size
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What metamorphic rock forms during the metamorphism of limestone or dolostone?
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Marble
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Of the following rock types, which is characterized by the segregation of light- and dark-colored minerals into thin layers or bands?
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Granitic Gneiss
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In which setting would regional metamorphism be most likely?
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At great depths in the crust where two continents are colliding.
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What nonfoliated metamorphic rock forms during contact metamorphism of a shale or mudstone?
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Hornfels
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What term describes a strong, parallel alignment of coarse mica flakes and/or of different bands in a metamorphic rock?
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Foliation
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What is the major source of heat for contact metamorphism?
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Heat from nearby magma body
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What term describes the zone of contact metamorphism that surrounds an intrusive magma body?
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Aureole
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Which one of the following is not likely to be genetically associated with impact of an asteroid or large meteorite?
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Blueschists
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Which of the following situations would exhibit sheared and mechanically fragmented rocks?
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Fault movements at shallow depths
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Which low-grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, typically exhibits well developed rock cleavage?
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Slate
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What metamorphic environment produces tektites?
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High temperatures associated with meteorite impacts
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What metamorphic rock forms from sandstone?
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Quartzite
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Which of the following lists foliated metamorphic rocks in the order of increasing grain size and increasing grade of metamorphism?
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Slate, phyllite, and schist
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What foliated, metamorphic rock is texturally intermediate between slate and schist?
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Phyllite
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Which of the following best describes the conditions of contact metamorphism?
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Pressures are fairly low, the rock may be in the upper part of the crust, and heat is supplied from a nearby magma body such as a pluton dike, or sill.
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What type of foliation results from the parallel alignment of abundant, coarse-grained, mica flakes in a metamorphic rock?
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Schistosity
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Which of the following statements concerning slate is not true?
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Slate has abundant, coarse-grained mica.
