SolutionsgManualgforgEssentialsgofgGeology,g5egbygStephengM
arshakg(AllgChapters)
CHAPTERg1
ThegEarthgingContext
LearninggObjectives
1. StudentsgshouldgbegawaregofgthegBiggBanggtheory.gDistantggalaxiesgaregallgmo
vinggawaygfromgus.gThegfarthestggalaxiesgaregrecedinggfromgusgthegfastest.gAll
gmattergingthegUniversegwasgcontainedgingagsinglegpoint,gapproximatelyg13.8gbi
lliongyearsgago.gAtgthatgtime,gthegUniversegexplosivelygcamegintogexistence.
2. Stars,gincludinggourgSun,garegnuclear-
fusiongreactors.gForgmostgofgtheirglifeghistoriesg(ongthegordergofgbillionsgofgye
ars),ghydrogengatomsgaregfusedgtogethergtogformghelium.gLatergstagesgingstellar
gevolutiongincludegfusiongofgheliumgatomsgandgother,gheaviergelements;gultimat
ely,girongisgthegheaviestgelementgthatgcangbegproducedgthroughgfusiongreactions
gwithingstars.
3. Aftergtheirgcyclesgofgfusiongaregcomplete,glargegstarsgviolentlygexplodeg(for
minggsupernovas),gproducinggelementsgheaviergthangirongandgleavinggbehind
gagresiduegofgdiffusegnebulae,gwhichgmaygbegrecycledgtogformgagnewgstarga
tgsomegfuturegpoint.
4. OurgSolargSystemgisgapproximatelyg4.57gGag(billiongyearsgold).gAllgeightgplan
etsgrevolvegaroundgthegSungingcoplanar,gellipticalgorbits.gAllgplanetsgorbitgingth
egsamegdirectiong(counterclockwise,gasgviewedgfromgabovegEarth’sgNorthgPole).
gThesegfactsgimplygsimultaneousgplanetarygformationgfromgagswirlinggnebulagsu
rroundinggthegSung(thegsimilaritiesgingorbitsgwouldgthengbegagnaturalgresultgofg
conservationgofgangulargmomentum).gThegplanetsgaccretedgfromgthisgnebulagthr
oughggravitationalgattractiongandghaphazardgcollisions.gPluto,glonggconsideredgth
eg“ninthgplanet,”ghasgseengitsgstatusgdemoted;gastronomersgnowgrecognizegeight
gmajorgplanets.
5. Thegterrestrialgplanetsg(Mercury,gVenus,gEarth,gandgMars)garegrelativelygsmall,
,gdense,gandgrockygworlds.gTheggiantgplanetsgaregpredominantlygcomposedgofgt
heglightggasesghydrogengandgheliumg(JupitergandgSaturn)gorgicesg(Uranusgandg
Neptune);gtheygare
, muchglargergandgmuchglessgdensegthangthegterrestrialgplanets.
6. OurgMoongisgthoughtgtoghavegoriginatedgfromgdebrisgaccumulatedgwhengagpro
toplanetgcollidedgwithgEarthgapproximatelyg4.53gGa.
7. ThegEarthgSystemgisgsubdividedgintogthegatmosphereg(gasesgandgaerosolsgthatg
envelopgthegplanet),ghydrosphereg(Earth’sgwater),ggeosphereg(solidgEarth),gandg
biosphereg(livinggthings).
8. Earthgisgchemicallygdividedgintogagthin,grockygcrustgdominatedgbygsilicategmine
rals,gagthickgmantlegcomposedgmostlygofgiron-gandgmagnesium-
richgsilicatesg(subjectglocallygtogpartialgmelting),gandgagthick,gmetallicgcoregma
degprimarilygofgirong(thegoutergportiongofgwhichgisgliquid).gStudentsgshouldgkno
wghowgseismicgwavesgtellgusgthatgthegoutergcoregmustgbegliquid.
9. Physically,gtheguppermostglayersgofgEarthgaregthegrigidglithosphereg(crustgandg
uppermostgmantle)gandgthegasthenosphere,gwhichgisgweakergandgflowsgplasticall
y.gTheg“plates”gofgplategtectonicsgtheorygaregdiscretegslabsgofglithosphere,gwhic
hgmovegwithgrespectgtogoneganothergatopgthegasthenosphere.
SummarygfromgthegText
TheggeocentricgmodelgplacedgEarthgatgthegcentergofgthegUniverse.gTheghelioce
ntricgmodelgplacedgthegSungatgthegcenter.
ThegEarthgisgonegofgeightgplanetsgorbitinggthegSun.gThegSolargSystemgliesgon
gthegoutergedgegofgthegMilkygWayggalaxy.gThegUniversegcontainsghundredsgofgbilli
onsgofggalaxies.
MostgastronomersgagreegthatgthisgexpansiongbegangaftergthegBiggBang,gagcata
clysmicgexplosiongthatgoccurredgaboutg13.7gbilliongyearsgago.
Thegfirstgatomsg(hydrogengandghelium)gofgthegUniversegdevelopedgwithingmin
utesgofgthegBiggBang.gThesegatomsgformedgvastggasgclouds,gcalledgnebulae.
OnlygverygsmallgatomsgformedgduringgBiggBanggnucleosynthesis.gThegEarth,ga
ndgtheglifegformsgongit,gcontaingelementsgthatgcouldghavegbeengproducedgonlygduri
nggtheglifegcycle
, ofgstars—intermediate-
sizedgatomsgformedgbygfusiongduringgsupernovaegexplosions.gThus,gwegaregall
gmadegofgstardust.
Gravitygcausedgclumpsgofggasgingthegnebulaegtogcoalescegintogflattenedgdisks
gwithgbulbousgcenters.gAsgthegcentralgballgofgthisgaccretionarygdiskgcollapsedginw
ard,gitgbecamegagwarmgprotostar.gEventually,gthegballgbecamegsoghotgandgdensegt
hatgfusiongreactionsgbegan,gandgitgbecamegagtruegstar.
Planetsgdevelopedgfromgnebulae,gthegringsgofggasgandgdustgsurroundinggnewbo
rngstars.gMattergingthesegnebulaegcondensedgintogplanetesimals,gwhichgthengclumpe
dgtogethergtogformgprotoplanets,gandgfinally,gtruegplanets.gInnergringsgbecamegthegt
errestrialgplanets;goutergringsggrewgintoggiantgplanets,gwhichgconsistgmostlygofggas
gand/orgice.
ThegMoongformedgfromgdebrisgejectedgwhengagprotoplanetgcollidedgwithgEart
hgingthegyounggSolargSystem.
Whengagprotoplanetggrowsglargegenough,gitgeventuallygbecomesgwarmgenough
ginsidegtogdifferentiategintogagcoregandgmantle,gandgthengtogassumegagnear-
sphericalgshapegwhengitgbecomesgsogsoftgthatggravitygcangsmoothgoutgirregularities.
ThegEarthghasgagmagneticgthatgshieldsgitgfromgsolargwindgandgcosmicgrays.
AglayergofggasgsurroundsgthegEarth.gThisgatmosphere,gwhichgconsistsgofg78
%gN2,g21%gO2,gandg1%gotherggases,gcangbegsubdividedgintoglayers.gAirgpressure
gdecreasesgwithgincreasinggelevation.
ThegsurfacegofgEarthgcangbegdividedgintoglandg(30%)gandgoceang(70%).gMo
stgofgtheglandgsurfacegliesgwithing1gkmgofgseaglevel.gEarth’sglandgsurfaceghasgag
greatgvarietygofglandscapesgduegtogvariationsgingelevationgandgclimate.
Earthgmaterialsgincludegorganicgchemicals,gminerals,gglasses,grocks,gmelts,gan
dgvolatiles.gMostgrocksgongEarthgcontaingsilicag(SiO2).gWegdistinguishgamonggvari
ousgbasicgrockgtypesgbasedgongthegproportiongofgsilica.
ThegEarth’sginteriorgcangbegdividedgintogthreegdistinctglayers:gthegverygthingc
rust,gthegrockygmantle,gandgthegmetallicgcore.
PressuregandgtemperaturegbothgincreasegwithgdepthgingthegEarth.gThegratega
tgwhichgtemperaturegincreasesgasgdepthgincreasesgisgtheggeothermalggradient.
Thegcrustgisgagthingskingthatgvariesgingthicknessgfromg7–
10gkmg(beneathgoceans)gtog25–
70gkmg(beneathgthegcontinents).gOceanicgcrustgisgmaficgingcomposition,gwhereas
arshakg(AllgChapters)
CHAPTERg1
ThegEarthgingContext
LearninggObjectives
1. StudentsgshouldgbegawaregofgthegBiggBanggtheory.gDistantggalaxiesgaregallgmo
vinggawaygfromgus.gThegfarthestggalaxiesgaregrecedinggfromgusgthegfastest.gAll
gmattergingthegUniversegwasgcontainedgingagsinglegpoint,gapproximatelyg13.8gbi
lliongyearsgago.gAtgthatgtime,gthegUniversegexplosivelygcamegintogexistence.
2. Stars,gincludinggourgSun,garegnuclear-
fusiongreactors.gForgmostgofgtheirglifeghistoriesg(ongthegordergofgbillionsgofgye
ars),ghydrogengatomsgaregfusedgtogethergtogformghelium.gLatergstagesgingstellar
gevolutiongincludegfusiongofgheliumgatomsgandgother,gheaviergelements;gultimat
ely,girongisgthegheaviestgelementgthatgcangbegproducedgthroughgfusiongreactions
gwithingstars.
3. Aftergtheirgcyclesgofgfusiongaregcomplete,glargegstarsgviolentlygexplodeg(for
minggsupernovas),gproducinggelementsgheaviergthangirongandgleavinggbehind
gagresiduegofgdiffusegnebulae,gwhichgmaygbegrecycledgtogformgagnewgstarga
tgsomegfuturegpoint.
4. OurgSolargSystemgisgapproximatelyg4.57gGag(billiongyearsgold).gAllgeightgplan
etsgrevolvegaroundgthegSungingcoplanar,gellipticalgorbits.gAllgplanetsgorbitgingth
egsamegdirectiong(counterclockwise,gasgviewedgfromgabovegEarth’sgNorthgPole).
gThesegfactsgimplygsimultaneousgplanetarygformationgfromgagswirlinggnebulagsu
rroundinggthegSung(thegsimilaritiesgingorbitsgwouldgthengbegagnaturalgresultgofg
conservationgofgangulargmomentum).gThegplanetsgaccretedgfromgthisgnebulagthr
oughggravitationalgattractiongandghaphazardgcollisions.gPluto,glonggconsideredgth
eg“ninthgplanet,”ghasgseengitsgstatusgdemoted;gastronomersgnowgrecognizegeight
gmajorgplanets.
5. Thegterrestrialgplanetsg(Mercury,gVenus,gEarth,gandgMars)garegrelativelygsmall,
,gdense,gandgrockygworlds.gTheggiantgplanetsgaregpredominantlygcomposedgofgt
heglightggasesghydrogengandgheliumg(JupitergandgSaturn)gorgicesg(Uranusgandg
Neptune);gtheygare
, muchglargergandgmuchglessgdensegthangthegterrestrialgplanets.
6. OurgMoongisgthoughtgtoghavegoriginatedgfromgdebrisgaccumulatedgwhengagpro
toplanetgcollidedgwithgEarthgapproximatelyg4.53gGa.
7. ThegEarthgSystemgisgsubdividedgintogthegatmosphereg(gasesgandgaerosolsgthatg
envelopgthegplanet),ghydrosphereg(Earth’sgwater),ggeosphereg(solidgEarth),gandg
biosphereg(livinggthings).
8. Earthgisgchemicallygdividedgintogagthin,grockygcrustgdominatedgbygsilicategmine
rals,gagthickgmantlegcomposedgmostlygofgiron-gandgmagnesium-
richgsilicatesg(subjectglocallygtogpartialgmelting),gandgagthick,gmetallicgcoregma
degprimarilygofgirong(thegoutergportiongofgwhichgisgliquid).gStudentsgshouldgkno
wghowgseismicgwavesgtellgusgthatgthegoutergcoregmustgbegliquid.
9. Physically,gtheguppermostglayersgofgEarthgaregthegrigidglithosphereg(crustgandg
uppermostgmantle)gandgthegasthenosphere,gwhichgisgweakergandgflowsgplasticall
y.gTheg“plates”gofgplategtectonicsgtheorygaregdiscretegslabsgofglithosphere,gwhic
hgmovegwithgrespectgtogoneganothergatopgthegasthenosphere.
SummarygfromgthegText
TheggeocentricgmodelgplacedgEarthgatgthegcentergofgthegUniverse.gTheghelioce
ntricgmodelgplacedgthegSungatgthegcenter.
ThegEarthgisgonegofgeightgplanetsgorbitinggthegSun.gThegSolargSystemgliesgon
gthegoutergedgegofgthegMilkygWayggalaxy.gThegUniversegcontainsghundredsgofgbilli
onsgofggalaxies.
MostgastronomersgagreegthatgthisgexpansiongbegangaftergthegBiggBang,gagcata
clysmicgexplosiongthatgoccurredgaboutg13.7gbilliongyearsgago.
Thegfirstgatomsg(hydrogengandghelium)gofgthegUniversegdevelopedgwithingmin
utesgofgthegBiggBang.gThesegatomsgformedgvastggasgclouds,gcalledgnebulae.
OnlygverygsmallgatomsgformedgduringgBiggBanggnucleosynthesis.gThegEarth,ga
ndgtheglifegformsgongit,gcontaingelementsgthatgcouldghavegbeengproducedgonlygduri
nggtheglifegcycle
, ofgstars—intermediate-
sizedgatomsgformedgbygfusiongduringgsupernovaegexplosions.gThus,gwegaregall
gmadegofgstardust.
Gravitygcausedgclumpsgofggasgingthegnebulaegtogcoalescegintogflattenedgdisks
gwithgbulbousgcenters.gAsgthegcentralgballgofgthisgaccretionarygdiskgcollapsedginw
ard,gitgbecamegagwarmgprotostar.gEventually,gthegballgbecamegsoghotgandgdensegt
hatgfusiongreactionsgbegan,gandgitgbecamegagtruegstar.
Planetsgdevelopedgfromgnebulae,gthegringsgofggasgandgdustgsurroundinggnewbo
rngstars.gMattergingthesegnebulaegcondensedgintogplanetesimals,gwhichgthengclumpe
dgtogethergtogformgprotoplanets,gandgfinally,gtruegplanets.gInnergringsgbecamegthegt
errestrialgplanets;goutergringsggrewgintoggiantgplanets,gwhichgconsistgmostlygofggas
gand/orgice.
ThegMoongformedgfromgdebrisgejectedgwhengagprotoplanetgcollidedgwithgEart
hgingthegyounggSolargSystem.
Whengagprotoplanetggrowsglargegenough,gitgeventuallygbecomesgwarmgenough
ginsidegtogdifferentiategintogagcoregandgmantle,gandgthengtogassumegagnear-
sphericalgshapegwhengitgbecomesgsogsoftgthatggravitygcangsmoothgoutgirregularities.
ThegEarthghasgagmagneticgthatgshieldsgitgfromgsolargwindgandgcosmicgrays.
AglayergofggasgsurroundsgthegEarth.gThisgatmosphere,gwhichgconsistsgofg78
%gN2,g21%gO2,gandg1%gotherggases,gcangbegsubdividedgintoglayers.gAirgpressure
gdecreasesgwithgincreasinggelevation.
ThegsurfacegofgEarthgcangbegdividedgintoglandg(30%)gandgoceang(70%).gMo
stgofgtheglandgsurfacegliesgwithing1gkmgofgseaglevel.gEarth’sglandgsurfaceghasgag
greatgvarietygofglandscapesgduegtogvariationsgingelevationgandgclimate.
Earthgmaterialsgincludegorganicgchemicals,gminerals,gglasses,grocks,gmelts,gan
dgvolatiles.gMostgrocksgongEarthgcontaingsilicag(SiO2).gWegdistinguishgamonggvari
ousgbasicgrockgtypesgbasedgongthegproportiongofgsilica.
ThegEarth’sginteriorgcangbegdividedgintogthreegdistinctglayers:gthegverygthingc
rust,gthegrockygmantle,gandgthegmetallicgcore.
PressuregandgtemperaturegbothgincreasegwithgdepthgingthegEarth.gThegratega
tgwhichgtemperaturegincreasesgasgdepthgincreasesgisgtheggeothermalggradient.
Thegcrustgisgagthingskingthatgvariesgingthicknessgfromg7–
10gkmg(beneathgoceans)gtog25–
70gkmg(beneathgthegcontinents).gOceanicgcrustgisgmaficgingcomposition,gwhereas
