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22 Cards in this Set

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