8.5: Activity 8D - Magma Viscosity
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The following questions address what factors control how fast a melt can flow. The viscosity, a material’s resistance to flow, depends primarily on the melt composition, but can also be affected by temperature and gas release.
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Intermediate lavas can flow ??? than mafic lavas, due to the ??? viscosity.
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slower, higher
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slower, lower
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faster, higher
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faster, lower
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Consider (or actually try) the following, if we compare how honey (or dark corn syrup) and water flow when poured from a container,
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then the honey (corn syrup) represents felsic magma, and the water represents mafic magma.
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then the honey (corn syrup) represents mafic magma, and the water represents mafic magma.
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Imagine putting the honey (corn syrup) in the refrigerator overnight; will its viscosity be affected?
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yes, the viscosity will increase
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yes, the viscosity will decrease
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no, there will be no change as the composition stays the same
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Keep the honey (corn syrup) in mind while you answer this question. When first erupted, basaltic lava typically erupts at around 2100°F. After flowing away from the vent, the temperature falls. How will the viscosity change as the lava flows away from the vent?
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Viscosity will increase.
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Viscosity will decrease.
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Viscosity will stay the same.
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