GEOL-1021EL Lecture Notes - Lecture 5: Crystallization, Water Content, Himalayas
16 Jun 2018
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Igneous Rocks
**Know the name of 6 rock-forming igneous minerals
About
•form from “liquid rock” (silicate melt)- is essentially the product of the cooling of the rock
•igneous processes within the earth produce intrusive (plutonic) igneous rocks
•igneous processes on/near the surface reduce extrusive (volcanic) igneous rocks
Magma V Lava
•Magma: mixture of molten rock (“melt”/“silicate melt”), plus crystals (minerals), coexisting
with the melt and gasses, if present.
•Lava: magma that has reached the surface
How do igneous rocks differ from each other?
•Texture
•Coarse-grained, fine-grained, mixed texture
•clues about texture can be received from early volcanic rocks, studies of granite and other
non-volcanic rocks, laboratory crystallization processes
•overall texture is related to the rate of cooling
•Intrusive (plutonic) is more coarse-grained (slow cooling)
•Extrusive (volcanic) is more fine-grained or even glassy (fast)
