ROCKS

What is a Rock?What is a Rock?

Naturally-occurring mixtures of Naturally-occurring mixtures of mineralsminerals, mineraloids (no crystals), , mineraloids (no crystals), or organic matter.or organic matter.

Types of Rocks…Types of Rocks… The The threethree main main kinds of rockkinds of rock are are

igneous, sedimentary and igneous, sedimentary and metamorphic rock.metamorphic rock.– Igneous rockIgneous rock: forms when : forms when

magma/lava cools and hardensmagma/lava cools and hardens– Sedimentary rock:Sedimentary rock: forms when forms when

sedimentssediments are are buried, buried, compacted & cemented togethercompacted & cemented together

– Metamorphic rock:Metamorphic rock: forms when forms when existing rockexisting rock is subjected to is subjected to great great heat & pressureheat & pressure over a over a long period of timelong period of time

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

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

Formed from the cooling of either Formed from the cooling of either magma or magma or lavalava

The most The most abundantabundant type of rock type of rock

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

Igneous Rocks come from magma/lava Igneous Rocks come from magma/lava cooling down.cooling down.

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) Cooling could have taken ) Cooling could have taken hundreds of years.hundreds of years.

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))

Granite: Intrusive or Granite: Intrusive or Extrusive? Why? Extrusive? Why?

Obsidian: Intrusive or Obsidian: Intrusive or Extrusive? Why? Extrusive? Why?

COMPOSITIONCOMPOSITION— — What kind of What kind of substances or minerals are rocks made substances or minerals are rocks made

ofof

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..

Diorite-has course grainsDiorite-has course grains

Basalt-no course grainsBasalt-no course grains

GraniteGranite

Formed from Formed from sedimentssediments (rock (rock fragments, mineral fragments, mineral grains, animal & plant grains, animal & plant remains-shells, bones, remains-shells, bones, leaves, stems) that are leaves, stems) 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 then deposited water, ice or gravity then deposited into layers.into layers.

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 -carrying rocks.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)

Elements of Erosion are heat, cold, Elements of Erosion are heat, cold, rain, waves, and grinding ice.rain, waves, and grinding ice.

At first sediments fit together At first sediments fit together loosely, over long periods of time, loosely, over long periods of time, thick layers build up. Because of the thick layers build up. Because of the heavy layers, the upper layers press heavy layers, the upper layers press down on the layers below them, down on the layers below them, causing Compaction.causing Compaction.

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

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. Formed when rock fragments are Formed when rock fragments are squeezed together.squeezed together.

Clastic-Sedimentary RocksClastic-Sedimentary Rocks

Shale: Formed Shale: Formed from tiny particles from tiny particles of clay compacted of clay compacted together.together.

Sandstone: Forms Sandstone: Forms from the from the compaction and compaction and cementation of cementation of small particles of small particles of sand.sand.

Clastic-Sedimentary RocksClastic-Sedimentary Rocks

Conglomerate: Formed Conglomerate: Formed from fragments of from fragments of various sizes of rocks various sizes of rocks and pebbles. and pebbles. Fragments are rounded Fragments are rounded because they have because they have been worn along been worn along riverbeds.riverbeds.

Breccia: Fragments are Breccia: Fragments are jagged with sharp jagged with sharp edges. Formed from edges. Formed from various size of rocks various size of rocks and pebbles.and pebbles.

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

Organic refers to substances that once Organic refers to substances that once were part of living things or were made were part of living things or were made by living things which contain calcite or by living things which contain calcite or calcium carbonate. (Can be tested by calcium carbonate. (Can be tested by using acid)using acid)


Organic-Sedimentary RocksOrganic-Sedimentary Rocks Coal: Remains of Coal: Remains of

swamp plants buried in swamp plants buried in water or by volcanic ash.water or by volcanic ash.

Limestone: Formed by Limestone: Formed by hard shells of once living hard shells of once living things such as coral, things such as coral, clams, oysters, and clams, oysters, and snails. When they die snails. When they die their shells pile up and their shells pile up and are covered by other are covered by other sediments compacting sediments compacting and cementing them.and cementing them.

Types of LimestoneTypes of Limestone

Chalk-can be Chalk-can be naturally occurring naturally occurring and in rock form.and in rock form.

Coquina-made of Coquina-made of large fragments of large fragments of shells.shells.

ChemicalChemical——mineralsminerals dissolved dissolved in lakes, seas, or underground in lakes, seas, or underground water. Can occur when lakes water. Can occur when lakes evaporate.evaporate.


Chemical-Sedimentary RocksChemical-Sedimentary Rocks

Rock Salt: Made of Rock Salt: Made of the mineral halite.the mineral halite.

Gypsum: Formed Gypsum: Formed by evaporation in by evaporation in dry climates.dry climates.

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.

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)

How are metamorphic rocks How are metamorphic rocks classified? Look at Pages 162-163 classified? Look at Pages 162-163

in your booksin your books 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

Rocks TransformedRocks Transformed

Limestone Marble

Shale Slate

Rocks TransformedRocks Transformed

Sandstone Quartzite

Mudstone SchistGneiss

or

Say you have an unknown rock Say you have an unknown rock how do you classify it?how do you classify it?

Color: Like with Color: Like with minerals, color minerals, color alone does not alone does not provide enough provide enough information to information to identify a rock.identify a rock.


Texture can be very useful. Texture can be very useful. Look at and feel the rocks Look at and feel the rocks surface. surface.

Some are smooth and Some are smooth and glassy others are rough glassy others are rough and chalky.and chalky.

Grain Size: Large or SmallGrain Size: Large or Small Grain Shape: Fine Grained Grain Shape: Fine Grained

or Jaggedor Jagged Grain Patterns: Flat Grain Patterns: Flat

Layers, Wavy, banded, or Layers, Wavy, banded, or random.random.

No Visible Grain: Some No Visible Grain: Some cool to fast to have grains.cool to fast to have grains.


Mineral composition: Mineral composition: By looking under a By looking under a microscope, a microscope, a geologist can identify geologist can identify the minerals it the minerals it contains.contains.

You can use acid to You can use acid to check for carbonates. check for carbonates. (Limestone or Chalk)(Limestone or Chalk)


Origin: Where it came Origin: Where it came from!from!

Metamorphic: Usually Metamorphic: Usually have bigger crystals have bigger crystals because of increased because of increased heat and pressure.heat and pressure.

Igneous: Usually is made Igneous: Usually is made up of very large up of very large particles.particles.

Sedimentary: Small Sedimentary: Small solid pieces of material solid pieces of material that come from rocks or that come from rocks or living things. (Smoother)living things. (Smoother)

Rock Cycle AnimationsRock Cycle Animations

Rock Cycle Quiz Rock Cycle Animation #1Rock Cycle Animation #1 Weathering and Erosion Quiz Rock Cycle Video (Made by a M

iddle School Student) Go to the next slide to play Go to the next slide to play

Jeopardy.Jeopardy.

Jeopardy GameJeopardy Game

The Rock CycleThe Rock Cycle

The RockCycle

Igneous Rocks

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MetamorphicRocks

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Question 1Question 1

Mixture of minerals, volcanic glass, organic matter, or other material

Rock

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A model showing the processes that create and change rock.

Rock Cycle

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_________ rock can be changed by heat and pressure into metamorphic rock.

Sedimentary Rock

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__________ rock can be broken into fragments that may later form sedimentary rock.

Igneous

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______ rock can melt and cool to form igneous rock.

Metamorphic

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Magma reaches the surface flows from a volcano as ____________ .

Lava

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Magma trapped below the surface forms large – grained ______________ rock when it cools.

Intrusive

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Magma cooling at or near Earth’s surface forms small-grained __________ igneous rock.

Extrusive

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Igneous rocks are classified in 2 ways.

1.______________

2.______________

Intrusive and extrusive

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Question Question 1010

Volcanic glass rock __________ so quickly that few crystals form.

cool

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_____________ and ______________ result from one layer of rock on top of another layer.

Heat and pressure

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Sometime temperature and pressure are great enough to melt rock, forming ______________.

magma

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_____________ texture – mineral grains flatten and line up in parallel layers or bands.

Foliated texture

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_______ texture - mineral grains grow and rearrange but do not form layers.

Nonfoliated texture

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Sometimes ____________ flattens mineral grains in rocks without melting them.

Pressure

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Type of rock mostly found on the exposed surface of Earth.

Sedimentary Rock

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Sedimentary Rocks form in __________ .

layers

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Rock fragments, mineral grains, and bits of plants and animal remains moved by wind, water, ice or gravity are called _________________.

sediments

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When water and other minerals move through open spaced between larger sediments, gluing them together, ____________ occurs.

cementation

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_________ ___________ rocks are made from the remains of once – living plants or animals.

Organic sedimentary

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ROCKS

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