Download Metamorphic rock

Earth Science
Objectives:
1.
2.
3.
Describe two ways a rock can undergo
metamorphism.
Explain how the mineral composition of
rocks changes as the rocks undergo
metamorphism.
Describe the difference between foliated
and non-foliated metamorphic rock.
Origins of Metamorphic Rock
 Metamorphic
rocks
 Rocks in which the structure, texture, or
composition of the rock have changed
○ All three types of rock can be changed by heat, pressure,
or a combination of both
 A rock’s
texture or mineral composition can
change when its surroundings change
 If the temperature or pressure of the new
environment is different from the one in which the
rock formed
○ the rock will undergo metamorphism
1.
2.
Contact metamorphism
 When magma moves through the crust, the magma heats
the surrounding rock and changes it.
Regional metamorphism


occurs when pressure builds up in rock that is buried deep below other
rock formations
or when large pieces of the Earth’s curst collide with each other.
Composition of Metamorphic Rock
 As
rocks undergo metamorphism
 Original minerals in a rock change into new
minerals that are more stable in the new pressure
and temperature conditions.
 Index minerals (form only in metamorphic rock)
○ Are used to estimate
1. Temperature
2. Depth
3. Pressure ---- at which a rock undergoes metamorphism.
calcite
+
and
+ Heat
Pressure =
+
quartz
hematite
Garnet
Texture of Metamorphic Rock

Two types:
1. Foliated Metamorphic Rock
○ Mineral grains are arranged in planes or band
2.
Nonfoliated Metamorphic Rock
○ Mineral grains are not arranged in planes or band
○ commonly made of one or only a few minerals.
 This shows what happens to shale, a
sedimentary rock, when it is exposed to
more and more heat and pressure.
Shale
Slate
Phylite
Gneiss
Schist

Two examples of nonfoliated
metamorphic rock
undergoes
metamorphism
limestone
Marble
undergoes
metamorphism
Sandstone
Quartzite
Metamorphic Rock Structures
 Metamorphic
rock has features that indicates
its history. These features are caused by
deformation:
 Change in the shape of a rock caused by a force
placed on it.
○ These forces may cause a rock to be squeezed or
stretched.