Rocks: Materials of the Solid Earth - csus.edu · Bowen ’s reaction series Magma crystallizes over a temperature range of several hundred degrees Therefore, minerals crystallize

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Rocks: Materials of Rocks: Materials of

the Solid Earththe Solid Earth

Presentation modified from: Instructor Resource Center on CDPresentation modified from: Instructor Resource Center on CD--ROM, ROM, Foundations of Earth ScienceFoundations of Earth Science, 4, 4thth Edition, Edition, Lutgens/TarbuckLutgens/Tarbuck, ,

22TodayToday

�� Rock CycleRock Cycle

�� Igneous RocksIgneous Rocks

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Rock CycleRock Cycle

�� Shows the interrelationships among the three Shows the interrelationships among the three

rock typesrock types

�� Earth as a system: The Earth as a system: The rock cyclerock cycle

•• MagmaMagma

�� CrystallizationCrystallization

•• Igneous rockIgneous rock

�� WeatheringWeathering, , transportation, and depositiontransportation, and deposition

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�� Earth as a system: The rock cycleEarth as a system: The rock cycle

•• SedimentSediment

�� LithificationLithification

•• Sedimentary rockSedimentary rock

�� MetamorphismMetamorphism

•• Metamorphic rockMetamorphic rock

�� MeltingMelting

•• MagmaMagma

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�� Earth as a system: The rock cycleEarth as a system: The rock cycle

•• Full cycle does not always take place due to Full cycle does not always take place due to

"shortcuts" or interruptions"shortcuts" or interruptions

�� e.g., sedimentary rock meltse.g., sedimentary rock melts

�� e.g., igneous rock is metamorphosede.g., igneous rock is metamorphosed

�� e.g., sedimentary rock is weatherede.g., sedimentary rock is weathered

�� e.g., metamorphic rock weatherse.g., metamorphic rock weathers

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The Rock The Rock

CycleCycle

Figure 2.2

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77Rock Cycle QuestionsRock Cycle Questions

�� What do the colored What do the colored

arrows in Figure 2.2 arrows in Figure 2.2

represent?represent?

�� Where does the rock cycle Where does the rock cycle

““startstart”” and and ““endend””??

�� What is the source of What is the source of

energy for each arrow in energy for each arrow in

Figure 2.2? Choices areFigure 2.2? Choices are

�� EarthEarth’’s Internal Heats Internal Heat

�� GravityGravity

�� SunSun’’s Heats Heat

Figure 2.2

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Basic Rock TypesBasic Rock Types

�� Igneous RocksIgneous Rocks

�� Crystallize from Magma Crystallize from Magma (molten Earth material)(molten Earth material)

�� Sedimentary RocksSedimentary Rocks

�� From pieces of other From pieces of other rocks, orrocks, or

�� Chemical breakChemical break--down of down of other rocks or organismsother rocks or organisms

�� Metamorphic RocksMetamorphic Rocks

�� Alternation of other rocks Alternation of other rocks by high temperature and by high temperature and pressurepressure

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Igneous Rocks Igneous Rocks

�� Form as magma cools and crystallizesForm as magma cools and crystallizes

�� Rocks formed inside Earth are called Rocks formed inside Earth are called

plutonicplutonic or or intrusiveintrusive rocks rocks

�� Rocks formed on the surface Rocks formed on the surface

�� Formed from Formed from lavalava (a material similar to magma, (a material similar to magma,

but without gas)but without gas)

�� Called Called volcanicvolcanic or or extrusive extrusive rocksrocks

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1010Igneous RocksIgneous Rocks�� Form from Form from ““magmamagma””

�� Molten earth materialMolten earth material

�� Mineral crystals form Mineral crystals form

as magma coolsas magma cools

�� Like ice from waterLike ice from water

�� Magma on EarthMagma on Earth’’s s

surface is surface is ““LavaLava””

�� Cools rapidlyCools rapidly

�� ““ExtrudedExtruded””

�� ““ExtrusiveExtrusive””

igneous rocksigneous rocks

�� Magma below the EarthMagma below the Earth’’s surface is magmas surface is magma

�� Cools slowlyCools slowly

�� ““IntrudedIntruded”” into the crustinto the crust

�� ““IntrusiveIntrusive”” igneous rocksigneous rocks

Photograph by C.Heliker on October 3, 2003http://hvo.wr.usgs.gov/archive/spotlight_images/20031003-ch-0050.html

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�� Crystallization of magma Crystallization of magma

�� Ions are arranged into orderly patterns Ions are arranged into orderly patterns

�� Crystal size is determined by the rate of cooling Crystal size is determined by the rate of cooling

�� Slow rate forms large crystals Slow rate forms large crystals

�� Fast rate forms microscopic crystals Fast rate forms microscopic crystals

�� Very fast rate forms glassVery fast rate forms glass

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�� Classification is based on the rock's texture and Classification is based on the rock's texture and mineral constituents mineral constituents

�� Texture Texture

�� Size and arrangement of crystals Size and arrangement of crystals

�� TypesTypes

�� FineFine--grainedgrained——fast rate of coolingfast rate of cooling

�� CoarseCoarse--grainedgrained——slow rate of cooling slow rate of cooling

�� PorphyriticPorphyritic (two crystal sizes)(two crystal sizes)—— two rates of cooling two rates of cooling

�� GlassyGlassy——very fast rate of coolingvery fast rate of cooling

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Lava & Volcanic RocksLava & Volcanic Rocks

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Volcanic Rocks Volcanic Rocks ––

DevilDevil’’s Towers Tower

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Igneous Rocks Igneous Rocks -- GraniteGranite

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1616FineFine--Grained Grained

Igneous TextureIgneous Texture

Fig 2.4 A

1717CoarseCoarse--Grained Grained

Igneous TextureIgneous Texture

Fig 2.4 B

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Porphyritic Igneous TexturePorphyritic Igneous Texture

Fig 2.6

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1919Obsidian Exhibits Obsidian Exhibits

a Glassy Texturea Glassy Texture

Fig 2.7 A

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Igneous CompositionsIgneous Compositions

�� Composed mainly of silicate minerals Composed mainly of silicate minerals

�� Two major groups Two major groups

�� Dark silicates = rich in iron and/or magnesiumDark silicates = rich in iron and/or magnesium

�� Light silicates = greater amounts of potassium, Light silicates = greater amounts of potassium,

sodium, and calciumsodium, and calcium

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�� Granitic rocks Granitic rocks

�� Composed almost entirely of lightComposed almost entirely of light--colored colored

silicatessilicates——quartz and feldspar quartz and feldspar

�� Also referred to as Also referred to as felsic:felsic: fefeldspar and ldspar and sisilica (quartz)lica (quartz)

�� High silica content (about 70 percent) High silica content (about 70 percent)

�� Common rock is Common rock is granitegranite

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�� Basaltic rocks Basaltic rocks

�� Contain substantial dark silicate minerals and calciumContain substantial dark silicate minerals and calcium--

rich plagioclase feldspar rich plagioclase feldspar

�� Also referred to as Also referred to as mafic:mafic: mamagnesium and gnesium and feferrum (iron) rrum (iron)

�� Common rock is Common rock is basaltbasalt

2323Basalt Basalt

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�� Other compositional groups Other compositional groups

�� AndesiticAndesitic (or intermediate) (or intermediate)

�� Common volcanic rock is andesiteCommon volcanic rock is andesite

�� UltramaficUltramafic

�� Peridotite Peridotite

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2525Classification of Classification of

Igneous RocksIgneous Rocks

Figure 2.8

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How Different Igneous Rocks Form How Different Igneous Rocks Form

�� BowenBowen’’s reaction series s reaction series

�� Magma crystallizes over a temperature range of Magma crystallizes over a temperature range of

several hundred degreesseveral hundred degrees

�� Therefore, minerals crystallize in a predictable Therefore, minerals crystallize in a predictable

order order

�� Last minerals to crystallize are very different in Last minerals to crystallize are very different in

composition from the earlier formed minerals composition from the earlier formed minerals

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Figure 2.9

Bowen’s Reaction Series

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�� Magmatic differentiation Magmatic differentiation

�� Differentiation refers to the formation of one or Differentiation refers to the formation of one or

more secondary magmas from a single parent more secondary magmas from a single parent

magmamagma

�� One example of this is One example of this is crystal settlingcrystal settling

�� EarlierEarlier--formed minerals are denser than the liquid portion formed minerals are denser than the liquid portion

and sink to the bottom of the magma chamber and sink to the bottom of the magma chamber

2929These 2 rocks have the same chemical These 2 rocks have the same chemical

and mineralogical compositionand mineralogical composition

�� They are classified as different rock typesThey are classified as different rock types

�� How do they differ in appearance?How do they differ in appearance?

Figure 2.4

3030

These two rocks have the same textureThese two rocks have the same texture

�� They are classified as different rocksThey are classified as different rocks

�� How do they differ in appearance?How do they differ in appearance?

Figure 2.4a

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3131What criteria are used to classify What criteria are used to classify

igneous rocks?igneous rocks?

�� ““TextureTexture””

�� Coarse grained or fine grainedCoarse grained or fine grained

�� Mineral compositionMineral composition

�� Light colored (lots of quartz and feldspar)Light colored (lots of quartz and feldspar)

•• ““FelsicFelsic””

�� Dark colored (lots of Magnesium and Dark colored (lots of Magnesium and

Iron minerals)Iron minerals)

•• ““MaficMafic””

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A DemonstrationA Demonstration

�� I need a volunteerI need a volunteer……

3333Texture: CoarseTexture: Coarse--grainedgrained

�� Individual mineral crystals are visibleIndividual mineral crystals are visible

�� Cooled slowly (underground)Cooled slowly (underground)

�� IntrusiveIntrusive (or (or plutonicplutonic after Pluto after Pluto –– Greek Greek god of the underworld)god of the underworld)

Figure 2.4B

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Texture: FineTexture: Fine--grainedgrained

�� Cannot see individual crystals with naked eyeCannot see individual crystals with naked eye

�� Cooled rapidlyCooled rapidly

�� Extrusive (or volcanic)Extrusive (or volcanic)

Figure 2.4A

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Texture: GlassyTexture: Glassy

�� Did this rock cool slowly or rapidly?Did this rock cool slowly or rapidly?

�� In what environment might this rock have formed?In what environment might this rock have formed?

Figure 2.7A

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Texture: VesicularTexture: Vesicular

�� GasGas--escape bubbles escape bubbles

(vesicles)(vesicles)

�� Did this rock cool Did this rock cool

rapidly or slowly?rapidly or slowly?

�� Is this an intrusive Is this an intrusive

(plutonic) or (plutonic) or

extrusive (volcanic) extrusive (volcanic)

rock?rock?

Figure 2.5

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Tell me about the origin of this rockTell me about the origin of this rock

�� It is glassyIt is glassy

�� It contains vesiclesIt contains vesicles

�� It is called It is called ““pumicepumice””

Figure 2.7B

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Tell me about the origin of this rockTell me about the origin of this rock

�� It has some wellIt has some well--

developed crystals, butdeveloped crystals, but

�� It is mostly fine It is mostly fine

grainedgrained

(It is called porphyry)(It is called porphyry)

Figure 2.6

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Instant Recall ChallengeInstant Recall Challenge

�� Close your notes and books.Close your notes and books.

�� What are some igneous textures are what do they What are some igneous textures are what do they

indicate about the origin of the igneous rock?indicate about the origin of the igneous rock?

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4040What criteria are used to classify igneous rocks?What criteria are used to classify igneous rocks?

�� Appearance or Appearance or ““TextureTexture””

�� Coarse grainedCoarse grained

�� Fine grainedFine grained

�� Glassy Glassy

�� VesicularVesicular

�� PorphyriticPorphyritic

�� Mineral compositionMineral composition

�� Light colored (lots of quartz and feldspar)Light colored (lots of quartz and feldspar)

•• ““FelsicFelsic””

�� Dark colored (lots of Magnesium and Iron Dark colored (lots of Magnesium and Iron minerals)minerals)

•• ““MaficMafic””

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Two Compositions to worry aboutTwo Compositions to worry about

�� RhyoliteRhyolite (or Granite) Composition(or Granite) Composition

�� Basalt (or Basalt (or GabbroGabbro) Composition) Composition

Hand Samples

4242What are these rocks?What are these rocks?

GabbroGabbro BasaltBasalt

GraniteGranite RhyoliteRhyolite

Figure 2.4

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4343Rocks to be able to identify Rocks to be able to identify

these igneous rocksthese igneous rocks

�� GabbroGabbro

�� Coarse grained,Coarse grained,

�� Dark ColoredDark Colored

�� GraniteGranite

�� Coarse GrainedCoarse Grained

�� Light ColoredLight Colored

�� BasaltBasalt

�� Fine grainedFine grained

�� Dark ColoredDark Colored

�� RhyoliteRhyolite

�� Fine GrainedFine Grained

�� Light ColoredLight Colored

4444How and where did these rocks form?How and where did these rocks form?

ContinentalContinental

CrustCrust

OceanicOceanic

CrustCrust

4545Oceanic Versus Continental Igneous RocksOceanic Versus Continental Igneous Rocks

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4646

Recall from plate tectonicsRecall from plate tectonics

�� At what type of tectonic boundaries is new At what type of tectonic boundaries is new

crust formed?crust formed?

�� Is new crust usuallyIs new crust usually

�� (A) Oceanic (B) Continental (C) Either(A) Oceanic (B) Continental (C) Either ??

Divergent BoundariesDivergent Boundaries

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A good question:A good question:

�� If new crust is formed at divergent If new crust is formed at divergent

boundaries, and boundaries, and

�� If new crust has the composition of ocean If new crust has the composition of ocean

crust crust –– Basalt Basalt ––

�� Where does granite come from? Where does granite come from? (Or, how come continental crust is made of granite?)(Or, how come continental crust is made of granite?)

4848Can I get granite (or Can I get granite (or rhyoliterhyolite) by ) by

rere--crystallizing basalt?crystallizing basalt?

�� I have a piece of basaltI have a piece of basalt

�� I melt it to make magma (basaltic magma)I melt it to make magma (basaltic magma)

�� Now I let it cool (rapidly)Now I let it cool (rapidly)

�� What kind of rock will I end up with?What kind of rock will I end up with?

Think about this individually, then compare Think about this individually, then compare

your answer with your neighboryour answer with your neighbor’’s.s.

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4949To make a rock with a granite To make a rock with a granite

composition (granite or composition (granite or rhyoliterhyolite) from a ) from a

basaltic magma, I need to change the basaltic magma, I need to change the

chemistry of the magma!chemistry of the magma!

�� Granite (Granite (rhyoliterhyolite) has ) has

more silica than basalt more silica than basalt

(and (and gabbrogabbro))

�� Basalt (and Basalt (and gabbrogabbro) has ) has

more iron, calcium, and more iron, calcium, and

magnesium than granite magnesium than granite

(and (and rhyoliterhyolite))

Silic

a

Iron a

nd

Magn

esiu

m

Granite & Rhyolite

GabbroGabbro & &

BasaltBasalt

5050A thought experimentA thought experiment

�� I have a jar of jellybeans.I have a jar of jellybeans.

�� Half of the jellybeans are white, half are colored.Half of the jellybeans are white, half are colored.

�� In case you are wondering, the white jellybeans represent In case you are wondering, the white jellybeans represent silica, the colored jellybeans represent other elements silica, the colored jellybeans represent other elements (iron, magnesium, aluminum, etc.)(iron, magnesium, aluminum, etc.)

�� I periodically remove a handful of jellybeans from I periodically remove a handful of jellybeans from the jar. the jar.

�� With each handful I remove a few more colored With each handful I remove a few more colored jellybeans than white ones.jellybeans than white ones.

�� How will the How will the proportionproportion of white jellybeans change of white jellybeans change over time?over time?

�� Graph the proportion of white jellybeans with time.Graph the proportion of white jellybeans with time.

5151

A jellybean graphA jellybean graph

Time (Handfuls removed)

Pro

po

rtio

n o

f W

hit

e J

B’s

AA

BB

CC

50%50%

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5252BowenBowen’’s Reaction Series and Crystal s Reaction Series and Crystal

RemovalRemoval

OlivineOlivine

PyroxenePyroxene

AmphiboleAmphibole

SilicaSilica--Rich Rich

MagmaMagma

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�� BowenBowen’’s reaction series s reaction series

�� Magma crystallizes over a temperature range of Magma crystallizes over a temperature range of

several hundred degreesseveral hundred degrees

�� Therefore, minerals crystallize in a predictable Therefore, minerals crystallize in a predictable

order order

�� Last minerals to crystallize are very different in Last minerals to crystallize are very different in

composition from the earlier formed minerals composition from the earlier formed minerals

5454BowenBowen’’s Reaction Seriess Reaction Series

Figure 2.9

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BowenBowen’’s Reaction Series & Jellybeanss Reaction Series & Jellybeans

5656

From an Earlier Question About QuartzFrom an Earlier Question About Quartz

5757In groups: Speculate about how minerals In groups: Speculate about how minerals

might get separated from magma in might get separated from magma in

nature?nature?

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5858

Separation of Minerals By Crystal SettlingSeparation of Minerals By Crystal Settling

Figure 2.9

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Crystal SettlingCrystal Settling

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Rocks: Materials of the Solid Earth - csus.edu · Bowen ’s reaction series Magma crystallizes over a temperature range of several hundred degrees Therefore, minerals crystallize