Topic 23
Instrusive-(Cools and forms underground- large to medium sized cyrstals) They cool slowly
(Gabro,Granite,Dolorite,Diorite,Pereditie)
Three types- Batholiths, Dykes and Sills
Batholiths- Large cyrstals, Dome shaped, 100km, granite it the most common (Viscous)
Dykes- Medium Sized crystals, Disconcordant stuctures (Cuts across bedding) goes along lines of weakness, average of a metre thick.
Sills-Medium sized crystals, concordant structures, usually dolorite. 1-2 metres thick.
How do they get to the surface?
1) Weathering/erosion
2)Plate tectonics
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