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22 Cards in this Set
- Front
- Back
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Magma:
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molten rocks formed deep below the surface of the earth
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Lava:
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molten rocks formed at or near the surface of the earth
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Phaneritic texture:
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course-grained; took a long time to cool and crystals had time to form
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Aphanitic texture:
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fine-grained (can't see the texture); it cooled very quickly in volcanic environments
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Porphyritic texture:
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composed of at least 2 minerals having a big difference in grain size
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What are the two stages of porphyritic texture?
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large phenocysts form deep inside the earth; matrix grains crystallize closer to Earth's surface
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Glassy texture:
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non-crystalline with no mineral grains because they had no time to crystallize; display conchoidal fracture
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vesicular texture:
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refers to holes, pores, or cavities within the igneous rock; the result of gas expansion
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pyroclastic texture:
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numerous grains or fragments welded together by heat of volcanic eruption
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What is the range of silica for felsic rocks?
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65%
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What is the range of silica for intermediate rocks?
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55%-65%
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What is the range of silica for mafic rocks?
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45%-55%
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What is the range of silica for ultra-mafic rocks?
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less than 45%
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What color are felsic rocks and where are they formed?
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light; continents
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What color are mafic rocks and where are they formed?
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dark; oceans
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Laccolith:
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concordant, mushroom-shaped; pushes up but doesn't break through
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Batholith:
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usually discordant; must be 100 sq. km; largest of all intrusive, plutonic strucutures; majority contain felsic or intermediate magma
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Sill:
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concordant; shaped like a table
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Dike:
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discordant; cuts across existing rock layers; flat like a table
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Pegmatite:
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same basic minerals, but crystals are much larger in size; few inches to several hundred ft thick
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Granitization:
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process that the hot batholith pluton alters the surrounding country rock
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Stoping:
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occurs in the country rock; process of detaching pieces of country rock by rising magma
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