What is a Rock?What is a Rock?

Naturally-occurring mixtures of Naturally-occurring mixtures of mineralsminerals, mineraloids, glass or , mineraloids, glass or organic matter.organic matter.

What is a Rock?What is a Rock?

Rocks are divided into 3 groups Rocks are divided into 3 groups based on how they were formed:based on how they were formed:

IGNEOUSIGNEOUSSEDIMENTARYSEDIMENTARYMETAMORPHICMETAMORPHIC

What is the difference What is the difference between a rock and a between a rock and a

mineral?mineral? Rocks are made up of Rocks are made up of ONE or MOREONE or MORE

minerals.minerals.

Once a rock is formed, Once a rock is formed, does it stay the same does it stay the same

rock forever?rock forever? NONO!!

Rocks are Rocks are continually changedcontinually changed by many processes, such as by many processes, such as weathering, erosion, compaction, weathering, erosion, compaction, cementation, melting, and cementation, melting, and coolingcooling

Rocks can change to and from Rocks can change to and from the three typesthe three types

What is the process What is the process through which rocks through which rocks

change?change? The Rock Cycle—earth materials The Rock Cycle—earth materials

change back and forth among the change back and forth among the different types of rocksdifferent types of rocks

No set path a rock takes to become No set path a rock takes to become another kind of rockanother kind of rock

IGNEOUS

SEDIMENTARY METAMORPHIC

Weathering, Erosion, Compaction, Cementation

Recrystallization

Weathering, Erosion, Compaction, Cementation

Recrystallization

Melting, Solidification Melting,

Solidification

How are rocks How are rocks redistributed?redistributed?

The core, mantle, & crust are one The core, mantle, & crust are one giant rock giant rock recycling machinerecycling machine

***Watch the ***Watch the Rock Cycle by Rock Cycle by BrainpopBrainpop

1.1. What do igneous rocks form from?What do igneous rocks form from?

2.2. What kind of rock is sandstone?What kind of rock is sandstone?

3.3. What are metamorphic rocks What are metamorphic rocks formed by?formed by?

How can Starbursts How can Starbursts represent the Rock represent the Rock

Cycle?Cycle? Which rock form does your stacked Which rock form does your stacked Starbursts represent? Starbursts represent?

Now press your sedimentary rock in Now press your sedimentary rock in the palm of your hands for at least 2 the palm of your hands for at least 2 minutes (do not twist)minutes (do not twist)

What do you observe?What do you observe? Which type of rock does this Which type of rock does this

represent?represent?

Teacher DemonstrationTeacher Demonstration Watch as the new Starburst “rock” is Watch as the new Starburst “rock” is

melted. What do you notice?melted. What do you notice? What kind of rock is it now?What kind of rock is it now?

““Ignis” = Latin for “Ignis” = Latin for “firefire””

Formed from the cooling of either Formed from the cooling of either magma magma or lavaor lava

The most The most abundantabundant type of rock type of rock

Classified according to their Classified according to their originorigin and and compositioncomposition

ORIGINORIGIN— — Where rocks are formedWhere rocks are formed

Below groundBelow ground = from magma = from magma (intrusive igneous rock)(intrusive igneous rock)

Usually have Usually have LARGELARGE crystal grains (they crystal grains (they cooled cooled slowlyslowly))

Some have large & small crystals Some have large & small crystals (called porphyritic)(called porphyritic)

Above groundAbove ground = from lava = from lava (extrusive igneous rock)(extrusive igneous rock)

Usually have Usually have SMALL or NOSMALL or NO crystals (they crystals (they cooled too cooled too quicklyquickly))

PracticePractice Classifying Igneous Rocks as Classifying Igneous Rocks as intrusiveintrusive or or extrusiveextrusive——

Take out & classify these rocks from Take out & classify these rocks from your kits. Examine their crystals. your kits. Examine their crystals. Classify them (circle your choice) and Classify them (circle your choice) and tell why you did.tell why you did.

#5 Peridotite: Intrusive or #5 Peridotite: Intrusive or Extrusive? Why? Extrusive? Why?

#4 Granite: Intrusive or #4 Granite: Intrusive or Extrusive? Why? Extrusive? Why?

#11 Porphyry: Intrusive or #11 Porphyry: Intrusive or Extrusive? Why? Extrusive? Why?

#12 Obsidian: Intrusive or #12 Obsidian: Intrusive or Extrusive? Why? Extrusive? Why?

COMPOSITIONCOMPOSITION— — What kind of What kind of substances the rocks are made ofsubstances the rocks are made of

Basaltic Igneous RocksBasaltic Igneous Rocks ——made from lava/magma that is low in made from lava/magma that is low in silicasilica, rich in iron and magnesium. , rich in iron and magnesium.

Rocks are Rocks are dark-dark-coloredcolored..

Granitic Igneous RocksGranitic Igneous Rocks——made from magma/lava made from magma/lava highhigh in silica and oxygen. in silica and oxygen. Rocks are Rocks are lightlight-colored.-colored.

Andesitic Igneous RocksAndesitic Igneous Rocks—have a composition —have a composition between basaltic and between basaltic and graniticgranitic..

Practice Classifying Igneous Rocks Practice Classifying Igneous Rocks according to their composition:according to their composition:

#1: #1: DioriteDiorite

#8: #8: BasaltBasalt

#4: #4: GraniteGranite

Formed from Formed from sedimentssediments (rock (rock fragments, mineral fragments, mineral grains, animal & plant grains, animal & plant remains) that are remains) that are pressed or cemented pressed or cemented together or when together or when sediments sediments precipitateprecipitate out of a solution.out of a solution.

These sediments are moved by wind, These sediments are moved by wind, water, ice or gravity.water, ice or gravity.

Sedimentary rocks represent Sedimentary rocks represent 7%7% of of the Earth’s crust, but they cover the Earth’s crust, but they cover 70%70% of the Earth’s surface. of the Earth’s surface.

Sedimentary rocks are Sedimentary rocks are fossilfossil--carrying rocks.carrying rocks.

What turns sediments into solid rock?What turns sediments into solid rock?

Water or wind Water or wind breaks downbreaks down and and depositsdeposits sediment (erosion & sediment (erosion & deposition)deposition)

The heavy sediments The heavy sediments press downpress down on the layers beneath (compaction)on the layers beneath (compaction)

Dissolved minerals flow between the Dissolved minerals flow between the particles and particles and cementcement them together them together (cementation)(cementation)

How were most of the sedimentary How were most of the sedimentary rocks in the Puget Sound area rocks in the Puget Sound area

deposited?deposited?Glaciers about Glaciers about 15001500 years ago. years ago.

How can sedimentary layers help us How can sedimentary layers help us understand the age of fossils?understand the age of fossils?

As sedimentary As sedimentary rocks are rocks are deposited, they deposited, they form horizontal form horizontal layerslayers

Scientists know Scientists know that the layers on that the layers on toptop (and the (and the fossils in the top fossils in the top layer) are layer) are YOUNGERYOUNGER than than the fossils in lower the fossils in lower layers.layers.

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

ClasticClastic (also called Detrial)—made (also called Detrial)—made of of brokenbroken pieces of other rocks pieces of other rocks

OrganicOrganic—remains of —remains of plants and plants and animalsanimals are deposited in thick layers are deposited in thick layers

ExamplesExamples Fossil rich limestone is made from the Fossil rich limestone is made from the

shells of ocean animals; used to make shells of ocean animals; used to make chalkchalk

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

ChemicalChemical——mineralsminerals dissolved dissolved in lakes, seas, or underground in lakes, seas, or underground waterwater

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

Mineral crystals are made as the shallow water that has flooded the bottom of Death Valley evaporates. Click on image for full size (66K JPG)

Courtesy of Martin Miller, University of Oregon

ExamplesExamples LimestoneLimestone

made when made when calcite calcite mineral mineral precipitates precipitates from sea from sea water water

Rock SaltRock Salt——made from made from evaporation evaporation of sea watersof sea waters

Rocks that have changed due to Rocks that have changed due to intense intense temperaturetemperature and and pressurepressure

““Meta” means “Meta” means “changechange” and ” and morphosis means “morphosis means “formform” in Greek” in Greek

Igneous, sedimentary and other Igneous, sedimentary and other metamorphic rocks can change to metamorphic rocks can change to become metamorphic rocksbecome metamorphic rocks

What occurs in the Earth to What occurs in the Earth to change these rocks?change these rocks?

PressurePressure from overlying rock layers from overlying rock layersHigh High heatheat, but not enough to melt the rock, but not enough to melt the rockRocks may be Rocks may be flattenedflattened or bent or atoms or bent or atoms

may be exchanged to form new minerals.may be exchanged to form new minerals.

*You can think of metamorphic rocks *You can think of metamorphic rocks as a squished peanut butter & jelly as a squished peanut butter & jelly sandwich in your lunch.sandwich in your lunch.

How are metamorphic rocks How are metamorphic rocks classified?classified?

FoliatedFoliated—mineral grains are —mineral grains are flattened and line up in parallel flattened and line up in parallel bandsbands

ExampleExample: gneiss formed from : gneiss formed from rearrangement of minerals in granite rearrangement of minerals in granite into bandsinto bands

How are metamorphic rocks How are metamorphic rocks classified?classified?

Non-FoliatedNon-Foliated——NoNo bands are bands are formedformed

ExampleExample: marble formed from : marble formed from limestonelimestone

Where do metamorphic Where do metamorphic rocks usually form?rocks usually form?

Where magma Where magma intrudesintrudes relatively cool rockrelatively cool rock

Near Near collidingcolliding plates (near plates (near mountain ranges)mountain ranges)

Places that are covered miles Places that are covered miles thick with other rock causing thick with other rock causing pressurepressure

When hot water intrudes rockWhen hot water intrudes rock Where a Where a meteoritemeteorite strikes Earth strikes Earth

(rare)(rare) Where lightning bolts strike rocks Where lightning bolts strike rocks

(rare)(rare)