Chapter

Rocks

Rock Cycle Song(Sing to the tune of "Row, Row, Row Your Boat")

SEDIMENTARY rockHas been formed in layers

Often found near water sourcesWith fossils from decayers

Then there's IGNEOUS rockHere since Earth was bornHere since Earth was born

Molten Lava, cooled and hardenedThat's how it is formed

These two types of rocksCan also be transformed

With pressure, heat and chemicalsMETAMORPHIC they'll become.

3.1 The Rock Cycle

Rocks are any solid mass ofmineral or mineral-like matteroccurring naturally as part of our

Rocks

occurring naturally as part of ourplanet.

Types of Rocks

1. Igneous rock is formed by thecrystallization of molten magma.

Obsidian

3.1 The Rock Cycle

Types of Rocks

2. Sedimentary rock is formedfrom the weathered products ofpreexisting rocks that have beentransported, deposited,compacted, and cemented.

3.1 The Rock Cycle

Types of Rocks

3. Metamorphic rock is formed by3. Metamorphic rock is formed bythe alteration of pre-existing rockdeep within Earth (but still in thesolid state) by heat, pressure,and/or chemically active fluids.

3.1 The Rock Cycle

Shows the interrelationships amongthe three rock types (igneous,sedimentary, and metamorphic)

Magma is molten material thatforms deep beneath the Earth’ssurface.

Lava is magma that reaches thesurface.

3.1 The Rock Cycle

Weathering is a process in whichrocks are broken down by water, air,and living things.

Sediment is weathered pieces ofEarth elements.Earth elements.

The RockCycle

3.1 The Rock Cycle

Processes driven by heatfrom the Earth’s interior areresponsible for forming both

Energy That Drives the Rock Cycle

responsible for forming bothigneous rock

andmetamorphic rock.

3.1 The Rock Cycle

Weathering and the movement ofweathered materials are externalprocesses powered by energy

Energy That Drives the Rock Cycle

External processes producesedimentary rocks.

processes powered by energyfrom the sun.

3.2 Igneous Rocks

1. Intrusive igneous rocks areformed when magma hardensbeneath Earth’s surface - inside

Formation of Igneous Rocks

beneath Earth’s surface - inside

2. Extrusive igneous rocks areformed when lava hardens onEarth’s surface - outside

3.2 Igneous Rocks

1. Texture

Igneous rocks can be classifiedbased on their composition and

texture.

Classification of Igneous Rocks

1. Texture• Coarse-grained texture is causedby slow cooling resulting in largercrystals.

• Fine-grained texture is caused byrapid cooling resulting in smaller,interconnected mineral grains.

Course-Grained Igneous Texture

Granite is an intrusive igneous rock thatforms when magma cools slowly beneath

Earth’s surface.

Fine-Grained Igneous Texture

Rhyolite is an extrusive igneous rock that formswhen lave cools quickly at Earth’s surface.

Obsidian Exhibits a Glassy Texture.

• Glassy texture is caused by veryrapid cooling.

Porphyritic Igneous Texture

Andesite

• Porphyritic texture is caused bydifferent rates of cooling resultingin varied sized minerals.

3.2 Igneous Rocks

2. Composition

• Granitic compositionrocks are maderocks are mademostly of light-colored quartz andfeldspar.

3.2 Igneous Rocks

2. Composition (continued)• Basaltic composition rocks aremade mostly of dark-coloredsilicate minerals and plagioclasefeldspar.feldspar.

Peridotite

3.2 Igneous Rocks

2. Composition (cont)

• Andesitic composition rocks arebetween granitic light-colorbetween granitic light-colorminerals and basaltic compositiondark-colored minerals.

• Ultramafic composition rocks aremade mostly from iron andmagnesium-rich minerals.

Basalt

Basalt is an igneous rock made mostly of dark-colored silicate minerals.

Classification of Igneous Rocks

3.3 Sedimentary Rocks

1. Erosion involves the weathering

Weathering, Erosion, and Deposition

Formation of Sedimentary Rocks

1. Erosion involves the weatheringand the removal of rock.

2. Deposition occurs when an agentof erosion—water, wind, ice, orgravity—loses energy and dropssediments.

3.3 Sedimentary Rocks

3. Compaction is a process thatsqueezes, or compacts, sediments.

Compaction and Cementation

squeezes, or compacts, sediments.

4. Cementation takes place whendissolved minerals are deposited inthe tiny spaces among thesediments.

3.3 Sedimentary Rocks

1. Clastic sedimentary rocks arecomposed of weathered bits of

Two Main Groups

Classification of Sedimentary Rocks

composed of weathered bits ofrocks and minerals.

• Classified by particle size

- Shale (most abundant)

• Common rocks include- Conglomerate- Sandstone

Sandstone

Shale with Plant Fossils

Shale is a common clastic sedimentary rock.

Conglomerate

Made of rounded pebbles cemented together.

3.3 Sedimentary Rocks

Two Main Groups

2. Chemical sedimentary rocks formwhen dissolved substances

Classification of Sedimentary Rocks

when dissolved substancesprecipitate, or separate, from water.

3.3 Sedimentary Rocks

•Common Chemical sedimentaryrocks include

- limestone - most abundant

Classification of Sedimentary Rocks

- limestone - most abundant- microcrystalline quartz known aschert, flint, jasper, or agate

- evaporites such as rock salt orgypsum

- coal

Fossiliferous Limestone

This biochemical rock, called coquina, isa type of limestone that is made of

hundreds of shell fragments

Classification of Sedimentary Rocks

3.3 Sedimentary Rocks

Features of sedimentary rocks areclues to how and where the rocks

Features of Some Sedimentary Rocks

are formed Examples include where the

layer is in relation to otherlayers, fossils, ripple marks, andmud cracks

3.4 Metamorphic Rocks

Metamorphism means “to changeform.”

Most metamorphic changes occur

Formation of Metamorphic Rocks

Conditions for formation arefound a few kilometers below theEarth’s surface and extend into theupper mantle.

Most metamorphic changes occurat elevated temperatures andpressures.

3.4 Metamorphic Rocks

Contact metamorphism occurswhen magma moves into rock.

Formation of Metamorphic Rocks

•Changes are driven by a rise intemperature.

•Example: Marble

•Occurs near a body of magma

3.4 Metamorphic Rocks

Regional metamorphism resultsin large-scale deformation andhigh-grade metamorphism.

Formation of Metamorphic Rocks

high-grade metamorphism.

•Directed pressures and hightemperatures occur duringmountain building.

•Produces the greatest volume ofmetamorphic rock

3.4 Metamorphic Rocks

Heat•Provides the energy needed todrive chemical reactions

Agents of Metamorphism

Pressure (Stress)

drive chemical reactions•Two sources: magma and change intemperature with depth

•Causes a more compact rock withgreater density

Origin of Pressure inMetamorphism

3.4 Metamorphic Rocks

•Hot water-based solutions escaping

Hydrothermal Solutions

Agents of Metamorphism

•Hot water-based solutions escapingfrom the mass of magma

•Promote recrystallization bydissolving original minerals andthen depositing new ones

3.4 Metamorphic Rocks

1. Foliated Metamorphic Rock Two main categories

Classification of Metamorphic Rocks

2. Nonfoliated Metamorphic Rock

•Has a banded or layeredappearance

•Does not have a banded texture

Classification ofMetamorphic Rocks

Gneiss Typically Displays aBanded Appearance

Gneiss is a foliated metamorphic rock.

Marble—A NonfoliatedMetamorphic Rock