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How do igneous rocks form?
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Igneous rocks form by cooling and crystallization of molten rock.
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Whats the difference between lava and magma?
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Magma resides below the Earth's surface. Lava exists AT the the Earth's surface.
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What name do we give to igneous rocks that are produced below the Earth's surface?
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Plutons
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What is the difference between intrusive igneous rocks and extrusive igneous rocks?
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Instrusive (plutonic) igneous rocks form as magma cools and crstallizes within Earth. Extrusive (volcanic) igneous rocks form on the Earth's surface.
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What makes a highly viscous magma?
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High silica content.
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What determines the texture of an igneous rock?
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Cooling and crystallization.
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What determines whether or not crystals will form?
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Cooling rate of the lava/magma.
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What does texture refer to in igneous rocks?
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Size, shape and arrangement of mineral's grains.
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(VT) What is an aphanitic texture and what can we tell about a rock by observing said texture?
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An aphanitic texture = microscopic mineral grains. Aphanaitic textures indicate rapid cooling characteristic of volcanic igneous rock.
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What does quenching mean?
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Quenching is the process that occurs when a volcanic (extrusive) rock that cools so quickly it turns into a natural glass.
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How do vesicular textures occur?
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Gases become trapped in cooling lava and result in numerous small cavities and vesicles in the solidified rock.
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What are the characteristics of a pyroclastic rock?
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Angluar pieces of volcanic glass measuring up to 2mm.
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(PT) What does a phaneritic texture consist of?
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A phaneritic texture consists of an aggregate of large mineral grains, easily visible without magnifiction. Characteristic of plutonic igneous rocks.
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What are some characteristics of a porphyritic texture?
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Igneous composed of 2 or more markedly different grain sizes = porphyritic texture. Coarser grains = phenocrysts. Smaller grains = groundmass.
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Name the six minerals igneous rocks are made of.
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Quartz, feldspar, mica, amphibole, phyroxene and olivine.
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