5.3.5 Metamorphic Rocks

Metamorphic Rocks

p. 70

So gneiss!

​Metamorphic rocks have parents...parent rocks.

They can be sedimentary rocks, igneous rocks, or even other metamorphic rocks.

Sometimes they have grandparents and great-grandparents!

When these rocks are subjected to intense heat and pressure deep within the Earth, they undergo physical and chemical changes.

They become completely new types of rock with different characteristics.

basalt (3) schist (15)

​Metamorphic Rocks - rocks altered by extreme heat and pressure

Contact Metamorphism

Regional Metamorphism

Contact Metamorphism

• happens when rock changes due to coming into contact with magma

• intense heat changes the rocks without melting them completely creating new minerals and textures in the rock

​Common Parent	​Metamorphic Rock
​limestone (10)	​marble (12)
​shale (6) , mudstone	​hornfels
​quartz sandstone	​quartzite (13)

Regional Metamorphism

• occurs when a large area of rock is changed due to extreme pressure (and some heat).

• it is often the result of tectonic plates colliding

• the pressure comes from the pressure of the rocks above and the movement of Earth's surface

​Common Parent	​Metamorphic Rock
​shale (6) or mudstone	​slate (11)
shale (6) or mudstone	​schist (15)
​schist (15), granite (2), or shale (6)	​gneiss (14)

​Metamorphic Rocks - rocks altered by extreme heat and pressure

Contact Metamorphism

Regional Metamorphism

• Comes into contact with magma

• Primary cause of change is high heat

• Non-foliated

• Rock is under extreme pressure over a large area

• Primary cause is tectonic forces

• Foliated rocks

Foliation is a texture in some metamorphic rocks that refers to layers in the rock due to extreme pressure.

Pressure is applied in one direction, causing mineral crystals to reorient themselves perpendicular to the pressure.

Foliation gives the rock a striped or layered appearance.

Non-foliated vs Foliated

Marble (12)
Quartzite (13)

Slate (11)
Gneiss (14)
Schist (15)

Categorize

Options (6)

rocks are heated near magma

happens over large areas, often linked to mountain building

marble and quartzite

gneiss and schist

Match the statements and examples with the type of metamorphism

contact metamorphism

regional metamorphism

When rocks undergo metamorphosis, their minerals change. There are two main ways that heat and pressure change rock.

​	​Physical Changes
​Description	changes in the rock's structure and appearance
​Cause	mainly pressure
​Process example	​foliation: minerals align in layers
​Resulting appearance	​layered or banded appearance

​	​Chemical Changes
​Description	​changes in the rock's mineral composition
​Cause	​mainly heat and ion movement
​Process example	​recrystallization; new minerals form
​Resulting appearance	​crystaline texture with new mineral formations

• Construction - strength, aesthetic texture (beautiful, pleasing to the eye)
  

• Marble sculptures - reflect light to mimic skin and create depth
  

• Slate shingles - extremely durable, cleavage
  

The Parthenon -built about 550 BC (marble)

David created by Michalangelo 1501-1504

Washington Monument 555 ft tall (marble, granite, gneiss)

Multiple Choice

How are metamorphic rocks created?

• Heat & Pressure

• Melting & Solidification

• Compaction & Cementation

Multiple Choice

The word "foliated" means that

• Mineral crystals in a rock line up

• Intergrown crystals are visible

• The rock contains fossils

Multiple Choice

According to the rock cycle, any type of rock can become any other type of rock.

• True

• False

Open Ended

Look at your rocks. Tell me something interesting about one of your rocks. Be sure to tell me which rock you are discussing.