The Story of RocksThe Story of RocksHow did all of these

rocks get here?

Rock typesRock typesRock types are based on the way the rocks formed!

• Igneous

• Sedimentary

• Metamorphic

Rock types are based on the way the rocks formed!

• Igneous

• Sedimentary

• Metamorphic

IgneousIgneousIgneousIgneousThese rocks are formed from molten or These rocks are formed from molten or liquid rock.liquid rock.

Magma = liquid rock inside the EarthMagma = liquid rock inside the Earth

Lava = liquid rock on the surface.Lava = liquid rock on the surface.

SedimentarySedimentaryThese rocks are made of small fragments of These rocks are made of small fragments of rock cemented togetherrock cemented together

The small fragments are broken down from The small fragments are broken down from larger rocks by wind, water, and other forces and larger rocks by wind, water, and other forces and carried away.carried away.

Later they are deposited, buried deeper and Later they are deposited, buried deeper and deeper until they are compacted into rock.deeper until they are compacted into rock.

MetamorphicMetamorphicThese rocks start as igneous or These rocks start as igneous or sedimentary rocks.sedimentary rocks.

Rocks are changed by:Rocks are changed by:

1) heat1) heat

2) pressure2) pressure

3) chemical processes3) chemical processes

SedimentaryRocks

MetamorphicRock

MagmaIgneous

Rock

Sediments

Rock CycleRock Cycle

SedimentaryRocks

MetamorphicRock

MagmaIgneous

Rock

Sediments

Rock CycleRock Cycle

Igneous Rocks

Igneous RocksIgneous RocksThe main property of igneous rocks that allows us to identify which type of igneous rock that we have is – Texture

The texture is based on how large the crystals.

Crystal size depends on how fast the rock cooled (i.e. cooling rate)

Igneous Rocks

Igneous Rocks

Igneous RocksIgneous Rocks

Igneous RocksIgneous Rocks

Igneous RocksIgneous Rocks

Igneous RocksIgneous Rocks

Igneous Rocks

Sedimentary RocksSedimentary Rocks

Sedimentary RocksSedimentary RocksThe main property that allows us to group sedimentary rocks is the source of sediments.

Sediments can be:

1. Clastic

2. Chemical

3. Organic

The main property that allows us to group sedimentary rocks is the source of sediments.

Sediments can be:

1. Clastic

2. Chemical

3. Organic

Sedimentary RocksSedimentary Rocks• Clastic – These sediments are composed of

fragments that can be up to a meter in diameter or so small that the fragments cannot be seen with the naked eye.

• Clastic – These sediments are composed of fragments that can be up to a meter in diameter or so small that the fragments cannot be seen with the naked eye.

Sedimentary RocksSedimentary RocksChemical – These fragments were dissolved in water and usually form at the bottoms of rivers, lakes, seas, and oceans

Chemical – These fragments were dissolved in water and usually form at the bottoms of rivers, lakes, seas, and oceans

Sedimentary RocksSedimentary RocksOrganic – These fragments are from organic material like animals and plantsOrganic – These fragments are from organic material like animals and plants

Sedimentary RocksSedimentary Rocks• Common sedimentary features:

– Stratification (layering)– Ripple marks (from waves)– Cross bedding (different direction of beds)– Mud cracks (dried mud)– fossils (lithified animals and plants)– concretions

• Common sedimentary features:– Stratification (layering)– Ripple marks (from waves)– Cross bedding (different direction of beds)– Mud cracks (dried mud)– fossils (lithified animals and plants)– concretions

Sedimentary RocksSedimentary Rocks• Stratification• Stratification

Sedimentary RocksSedimentary Rocks• Ripple marks• Ripple marks

Sedimentary RocksSedimentary Rocks• Cross bedding• Cross bedding

Sedimentary RocksSedimentary Rocks• Mud Cracks• Mud Cracks

Sedimentary RocksSedimentary Rocks• Fossils• Fossils

Metamorphic RocksMetamorphic Rocks

Metamorphic RocksMetamorphic RocksMetamorphic rocks began their life as an igneous or sedimentary rock but underwent a physical change to become a new type of rock.

What causes the changes?1. Heat2 Pressure3. Chemicals

Metamorphic RocksMetamorphic RocksThere are two basic types of metamorphism:

1. Contact Metamorphism

2. Regional metamorphism

Metamorphic RocksMetamorphic RocksContact Metamorphism

Occurs when rocks near a magma chamber are exposed to high levels of heat but not melted

Metamorphic RocksMetamorphic RocksRegional Metamorphism

Occurs when rocks are exposed to tectonic pressure or heat.

Metamorphic RocksMetamorphic Rocks

Metamorphic RocksMetamorphic RocksHow do we classify metamorphic rocks since they have a wide range of compositions and origins?

Foliation!!

Definition: Visible parallel bands

(not layers)

Metamorphic rocks are foliated or unfoliated

Metamorphic RocksMetamorphic Rocks

Foliation occurs because the mineral grains are squished by the intense heat or pressure

Metamorphic RocksMetamorphic Rocks

Metamorphic RocksMetamorphic Rocks

Metamorphic RocksMetamorphic RocksUnfoliated