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Metamorphic Rocks Classified according to the arrangement of the grains that make up the rocks & the minerals in them A Rock Group in action…
Metamorphic Rocks
Classified according to the arrangement of the grains that make up the rocks & the minerals in them
A Rock Group in action…
Metamorphic rocks are nicknamed“Changing Rocks”.
Why?
They are made from other rocks…
How do Metamorphic rocks form?From heat & pressure deep inside Earth
Regional Metamorphism: Metamorphic rocks can form from Igneous, Sedimentary, or other Metamorphic rocks as they are pushed down toward the heat of the mantle.
Metamorphic Rocks: Contact Metamorphism
Contacting hot magma can change the surrounding rocks…
Stage 1 Mineral Alignment
Pressure
Heat
-Original parent rock with minerals in rock structure. (X,Y,Z).
- Rock is subject to low grade pressure & temperatures & then the minerals are flattened.
x
Y
xx
x Y
Y
Y
zz
zz
zx
x
z
Formation of Metamorphic Rocks
Stage 2 Banding
"Recrystallization" extreme heat & pressure allows individual crystals
to…
- Grow larger- Consolidate together- Separate according to density differences.
zzz
zzz zz zzz z
zz
zzz
xxx x x x
x xxx
x
x
x
xx
YY Y
Y YYYYYYz Y
Y
YY
zz z
z
x xx
xx
xYY
Y
Y
YY
2 Types of Metamorphic Rock
Foliated Nonfoliated
“Banded” “Nonbanded”
Foliated Metamorphic Rock• Definition: Grains arranged in layers or bands
that split into layers
• Examples:
Slate Schist Gneiss
Original Rock New Metamorphic Rock
Shale Slate
Shale (sedimentary) changes to Slate when heated & squeezed by pressure.
Original Rock New Metamorphic Rock
Granite Gneiss
Granite (Igneous) changes to Gneiss when heated & squeezed by pressure.
Nonfoliated Metamorphic Rock
• Definition: Mineral grains arranged randomly, do not split into layers
• Examples:Marble Quartzite
Original Rock New Metamorphic Rock
Sandstone Quartzite
When Sandstone (Sedimentary) is under extreme heat & pressure, Quartzite will form.
Identification of Metamorphic Rocks
Increasing Depth,Pressure & Temperature
Metamorphism Scale
Uses of Metamorphic Rocks
• Slate:
• Marble:
Old fashioned chalkboards, roofs, walkways, trim on buildings
*Sculptures (most famous – Lincoln Memorial in Washington D.C.)* Buildings
How are the 3 rock types related?
