1. Metamorphic Rocks

2. Metamorphic rock

3. Metamorphic rock
marble

4. An example of low-grade metamorphism is shale becoming slate.
Metamorphic Rocks
Metamorphic rocks are those that have changed their form due to external environmental issues.
Metamorphic rocks are produced from preexisting igneous, sedimentary, or even other metamorphic rocks.
Metamorphism takes place where preexisting rock is subjected to temperatures and pressures unlike those in which it formed.
There are different degrees of metamorphism which can be seen in the rock’s texture and in its mineralogy.
An example of low-grade metamorphism is shale becoming slate.
In high-grade metamorphism, obliteration of the rock’s original features occurs.

5. Metamorphic Rocks There are two basic types of rock metamorphism:
thermal or contact metamorphism
regional metamorphism

6. Metamorphic Rocks
Contact metamorphism is a type of metamorphism in which the mineralogy and texture of a body of rock are changed by exposure to the pressure and extreme temperature associated with a body of intruding magma.
Contact metamorphism often results in the formation of valuable minerals, such as garnet and emery, through the interaction of the hot magma with adjacent rock.

7. Metamorphic Rocks
During mountain-building, great quantities of rock are subjected to directed pressures and high temperatures associated with large-scale deformation called regional metamorphism.
Regional metamorphism is a type of metamorphism in which the mineralogy and texture of rocks are changed over a wide area by deep burial and heating associated with the large-scale forces of plate tectonics.
In regional metamorphism, rocks that form closer to the margin of the tectonic plates, where the heat and pressure are greatest, often differ in their minerals and texture from those that form farther away.

8. What Drives Metamorphism?
The driving agents of metamorphism include:
heat
pressure (stress) from burial (confining pressure) or from differential stress during mountain building
chemically active fluids (mainly water and other volatiles)

9. Pressure as a Metamorphic Agent

10. Metamorphic Textures
The degree of metamorphism is reflected in the rock’s texture and mineral composition.
When rocks are subjected to low-grade metamorphism, they become more compact and more dense (like slate.)
With high-grade metamorphism, stress causes certain minerals to re-crystallize. Consequently, many metamorphic rocks consist of visible crystals, much like coarse-grained igneous rocks.

11. Metamorphic Textures
The crystals of some minerals will recrystallize with a preferred orientation, essentially perpendicular to the direction of the compression force.
The resulting mineral alignment usually gives the rock a layered or banded appearance termed foliated texture. Examples: schist, gneiss

12. Some metamorphic rocks have a nonfoliated texture.
Metamorphic Textures
Some metamorphic rocks have a nonfoliated texture.
Metamorphic rocks composed of only one mineral that forms equidimensional crystals are, as a rule, not visibly foliated (examples: quartzite and marble.)

13. Common Metamorphic Rocks

14. Classification of Metamorphic Rocks

15. The Launch Pad
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1/3
Identify the rocks.
shale
slate

16. The Launch Pad
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2/3
Identify the rock.
gneiss

17. The Launch Pad
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3/3
Identify the rock.
marble