Metamorphic Rocks Rocks that are formed by heat and/or pressure 1/3/2019 Metamorphic Rocks Rocks that are formed by heat and/or pressure (but not completely melted) 1/3/2019

Metamorphic rocks are formed by: Regional metamorphism Involves mostly pressure Contact metamorphism Involves mostly heat 1/3/2019

Metamorphism by Pressure 1/3/2019 Metamorphism by Pressure What do you think causes enough pressure to metamorphose miles of rock? Introduce the notion of plate tectonics. 1/3/2019

Causes flattening of mineral crystals 1/3/2019

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Metamorphism by Pressure Pressure often causes realignment of intergrown mineral crystals Called banding Or foliation foliation banding 1/3/2019

1/3/2019 Banding These are not sedimentary layers but rather mineral crystals that have been flattened by metamorphism. 1/3/2019

Foliation 1/3/2019

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Regional Metamorphism Mountain building activity Involves large areas 1/3/2019

Large-scale metamorphism 1/3/2019

Known as contact metamorphism Metamorphism by Heat Known as contact metamorphism 1/3/2019

Contact Metamorphism Also known as thermal metamorphism 1/3/2019 Contact Metamorphism Also known as thermal metamorphism Creates baked rock ex. hornfels Show an example of hornfels 1/3/2019

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Contact Metamorphism Igneous intrusion Where molten rock is forced between existing rock Tends to bake (metamorphose) part of the existing rock 1/3/2019

Increasing degrees of metamorphism Rocks melt in this range 1/3/2019

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Composition of metamorphic rock is determined by: Conditions of metamorphism Mineralogy of parent (original) rock 1/3/2019

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 1/3/2019

shale slate In this example the minerals in shale actually change into other minerals during metamorphosis 1/3/2019

Some metamorphic rocks can form from several different parent rocks 1/3/2019 Some metamorphic rocks can form from several different parent rocks Ex. Gneiss may form from sandstone, shale or granite 1/3/2019

Where can you find this image? 1/3/2019

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? 1/3/2019

How to identify rocks Interlocking crystals? yes no Igneous/metamorphic sedimentary banding/foliation? no yes metamorphic igneous 1/3/2019

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 1/3/2019

Rock Cycle 1/3/2019

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 1/3/2019

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