GEOLOGY - Igneous Rocks
Terms
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- Where do magmas originate?
- Originate in the mantle
- In what 3 ways do magmas melt?
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1) Increase Temperature
2) Decompression melting
3) Flux Melting - What is "Flux Melting"?
- Introduce water to lower the melting point of the material
- What is decompression melting?
- release pressure due to stretching of lithosphere
- Characteristics of Intrusive rocks
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- deep underground
- slow cooling
- coarse grained - Characteristics of Extrusive rocks
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- near surface
- cool rapidly
- fine grained - Phaneritic
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- coarse grained
- large grains (seen with eye) - Porphoritic
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- 2 grain sizes
- phenocrysts embedded in smaller grains matrix - Aphanitic
- fine grained
- vesicular
- full of holes (gas bubbles)
- glassy texture
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- no grains
- rapid cooling rate
- commonly black - Ferromagnesian
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- more Fe and Mg present
- darker in color
ex: Gabbro, Basalt - Non-Ferromagnesian
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- less Fe and Mg present
- more silica present
- lighter color
ex: Granite, Rhyolite - What is Magmatic differentiation?
- how magmas change composition to form different igneous rock types
- What ways does magmatic differentiation occur?
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1) Crystalization - cools and crystalizes
2) Assimilation - melts and combines with other rock
3) mixes with other magma