1. Metamorphic Rocks Rocks that are formed by heat and/or pressure
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Metamorphic Rocks
Rocks that are formed by heat and/or pressure
(but not completely melted)
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2. Metamorphic rocks are formed by:
Regional metamorphism
Involves mostly pressure
Contact metamorphism
Involves mostly heat
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3. Metamorphism by Pressure
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Metamorphism by Pressure
What do you think causes enough pressure to metamorphose miles of rock?
Introduce the notion of plate tectonics.
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4. Causes flattening of mineral crystals
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7. Metamorphism by Pressure
Pressure often causes realignment of intergrown mineral crystals
Called banding
Or foliation
foliation
banding
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Banding
These are not sedimentary layers but rather mineral crystals that have been flattened by metamorphism.
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9. Foliation
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11. Regional Metamorphism
Mountain building activity
Involves large areas
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12. Large-scale
metamorphism
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13. Known as contact metamorphism
Metamorphism by Heat
Known as contact metamorphism
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14. Contact Metamorphism Also known as thermal metamorphism
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Contact Metamorphism
Also known as thermal metamorphism
Creates baked rock
ex. hornfels
Show an example of hornfels
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17. Contact Metamorphism Igneous intrusion
Where molten rock is forced between existing rock
Tends to bake (metamorphose) part of the existing rock
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18. Increasing degrees of metamorphism
Rocks
melt in
this
range
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20. Composition of metamorphic rock is determined by:
Conditions of metamorphism
Mineralogy of parent (original) rock
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21. In this example the mineral composition stays the same
Great heat and pressure
limestone
marble
(small crystals)
(large crystals)
In this example the mineral composition stays the same
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22. shale
slate
In this example the minerals in shale actually change into other
minerals during metamorphosis
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23. Some metamorphic rocks can form from several different parent rocks
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Some metamorphic rocks can form from several different parent rocks
Ex. Gneiss may form from sandstone, shale or granite
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24. Where can you find this image?
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25. When sandstone is subjected to heat and or pressure it becomes what?
 Is marble a foliated or non-foliated metamorphic rock?
 Name three minerals in schist
 What is the only metamorphic rock in your ESRT that exhibits banding?
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26. How to identify rocks Interlocking crystals? yes no
Igneous/metamorphic
sedimentary
banding/foliation? no
yes
metamorphic
igneous
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27. Rocks All rocks are classified on the basis of how they formed
Sedimentary rocks form from bits and pieces of existing rock
Igneous rocks form from molten minerals
Metamorphic rocks form from existing rocks that are changed by heat and/or pressure
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28. Rock Cycle
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29. Rock Cycle Nearly all rocks are formed from other rocks
Exceptions include
coal
Fossil limestone
Some rocks exist for thousands to billions of years before undergoing change
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