Chapter 6: Rocks...Metamorphic Rocks Metamorphic textures Foliated metamorphic rock –the...
Transcript of Chapter 6: Rocks...Metamorphic Rocks Metamorphic textures Foliated metamorphic rock –the...
Metamorphic Rocks
To get you thinking…
• Do you notice the
white bands rippling
through this cliff
face?
• How do you think this
occurred?
Metamorphic Rocks
Recognizing Metamorphic Rock
Metamorphism – the process in which one type of
rock changes into metamorphic rock because of
chemical processes or changes in temperature and
pressure
Heat &
Pressure
Limestone Marble
Metamorphic Rocks
Metamorphic Minerals
During metamorphism, heat, pressure, and hot fluids
cause some minerals to change into other minerals.
Minerals that change in this way are said to undergo
solid-state alterations.
Scientists identify the metamorphic conditions that create
specific minerals
When these minerals are found in a rock sample,
scientists are able to interpret the conditions inside the
crust during the rock’s metamorphism.
Metamorphic Rocks
Metamorphic textures
Foliated metamorphic rock – the metamorphic rock texture in which mineral grains are arranged in bands
Severe heat and pressure can cause minerals in rock to become flat or needlelike
This causes minerals to align in bands
Chemical bonds are usually weakened where these bands occur
Therefore metamorphic rock has a tendency to break along these bands.
Metamorphic Rocks
Foliated Metamorphic Rock
Metamorphic Rocks
Foliated Metamorphic Rock
Schist
Slate
Gneiss
Metamorphic Rocks
Metamorphic Rocks
Metamorphic textures
Nonfoliated metamorphic rock – the metamorphic
rock texture in which mineral grains are not arranged
in planes or bands
Nonfoliated rocks are composed of minerals that
form with blocky crystal shapes
Since nonfoliated rocks do not contain minerals that
align in bands, they are typically very strong and
durable
Metamorphic Rocks
Nonfoliated Metamorphic Rock
Marble
Quartzite
Hornfels
Metamorphic Rocks
Metamorphic Rocks
Types of Metamorphism
Regional metamorphism – occurs when changes in temperature and pressure affect large regions of Earth’s crust
This type of metamorphism usually occurs when one tectonic plate moves against another, which generates lots of heat and pressure in the rocks at the edges of the tectonic plates.
Most metamorphic rock is formed this way.
Metamorphic Rocks
Types of Metamorphism
Contact metamorphism – a local change in rock that
occurs due to contact with magma
Temperatures of rock decrease as the distance from magma increases
Metamorphic effects also decrease with distance
Contact metamorphism is limited to thin zones
Metamorphic Rocks
Metamorphic Rocks
Types of Metamorphism
Hydrothermal metamorphism – occurs when very hot
water reacts with rock and alters its chemical and
mineral composition
Typically occurs as hot fluids
migrate in and out of rock
during metamorphism
Valuable ore deposits of gold,
copper, zinc, tungsten and
lead form this way
End of Metamorphic Rocks