1. Metamorphic rocks form as existing rocks change.
Earth's Surface
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Metamorphic rocks form as existing rocks change.

2. Heat and pressure change rocks
Metamorphism is the process in which an existing rock is changed by heat and/or pressure
Parent rock can be sedimentary, igneous, or metamorphic rock.
The resulting rock is a metamorphic rock.
Limestone is the parent rock of marble, used by builders and artists.
Shale can be the parent rock of schist, a source of the gemstone garnet and a source of the mineral graphite

3. During metamorphism, rocks undergo many changes.
Pressure can cause a rock’s minerals to flatten out in one direction.
Minerals can change but the rock remains solid.
Rocks do not melt when they undergo metamorphism
High temperatures create an igneous rock
Heat and pressure can break the bonds that join atoms in minerals, which form new bonds
Two main results
Crystals can grow larger as more atoms join their crystal structures
New minerals can form in place of older ones as atoms combine in different ways
Ex. shale is formed from silt and clay but during recrystallization, garnet can form from these materials.

5. Metamorphic changes occur over large and small areas.
5A.When both temperature and pressure are high metamorphic changes can occur over very large areas.
6. In a region where large blocks of rock are pressing together and pushing up mountain ranges the process can affect an area hundreds of kilometers wide and tens of kilometers deep.
Rocks are buried, pressed together, bent, and heated, and the pressure and heat cause the rocks to undergo metamorphism.
Metamorphic changes are greater the deeper beneath the surface
Ex. A sedimentary rock may change to slate near the surface but become gneiss deep inside a mountain.

6. Metamorphic changes occur over large and small areas.
5B. Metamorphic changes can occur over small areas with either high temperature or high pressure.
Magma can push into rocks underground, or surface rock can be covered by a lava flow.
7A. Magma or lava heats rock and causes recrystallization
The thickness of rock changed depends on the temperature of the molten rock
7B.Rocks moving past each other during an earthquake can be exposed to pressures high enough to cause metamorphic changes

8. Most metamorphic rocks develop bands of minerals.
8. Foliation is present in most metamorphic rocks
Minerals are arranged in flat or wavy parallel bands.
Foliated rocks either split easily into leaflike sheets or have bands of minerals that are lined up and easy to see.
Develops when rocks are under pressure.
Common in rocks produced by metamorphic changes that affect large areas.
9A. Develops when minerals flatten out or line up in bands.
Bands are extremely thin at low levels of morphism
With higher pressure and temperature, the mineral mica can grow and make the rock look shiny, as is common in phyllite and schist.
9B. At high levels of metamorphism, the minerals tend to separate into light and dark bands, like those in gneiss.

10. Metamorphic rocks that do not show foliation are called nonfoliated rocks.
A metamorphic rock may not display foliation because it is made up of only one type of mineral.
Marble, which develops from limestone is used as a decorative stone because it does not split into layers as an artist is working with it
Quartzite forms from sandstone that is made up almost entirely of pieces of quartz.
A metamorphic rock may lack foliation because it has not been subjected to high pressure.
Hornfels often forms when magma or lava touches other rock