GEOL-1021EL Lecture Notes - Lecture 5: Crystallization, Water Content, Himalayas

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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)

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