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13 Cards in this Set
- Front
- Back
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What are factors that control melting temperature?
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Pressure, water, and mixed minerals
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Pressure
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It increases the melting point and reduces in pressure may cause melting
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Water
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An increase in water decreases melting point. Water under pressure (water vapor entrapped in magma) lowers the melting point
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Mixed Minerals
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Different minerals have various melting temperatures. Some combos may lower the overall melting temp.
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Identification of Igneous Rocks
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Texture and color
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Texture
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(size and arrangement of mineral grains) refers to the size, shape, and boundary relations between adjacent minerals in a rock
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What determines a rocks texture?
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They develop in response to the rate cooling of the magma and its viscosity
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Intrusive (Plutonic) Igneous Rocks
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Magmas deep within Earth's crust cool slowly
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Coarse Grained
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(visible crystals) phaneritic, individual minerals are large enough to be plainly visible
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Very Coarse Grained
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Pegmatites: consist of large crystalsm measured in cm/m (usually granitic)
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Extrusive(Volcanic) Igneous Rocks
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a magma extruded out onto Earth's surface cools rapidly and the crystals have only a short time to grow.
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Fine Grained
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(aphanitic) Can't be seen without microscope. Appear massive and structureless
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Glassy
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Extremly rapid cooling stops crystal growth
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