Solutions Manual
Essentials of Geology 5th Edition
by Stephen Marshak All Chapters Covered
, CHAPTER 1 j
The Earth in Context
j j j
LearningjObjectives
1. StudentsjshouldjbejawarejofjthejBigjBangjtheory.jDistantjgalaxiesjarejalljmovingjaw
ayjfromjus.jThejfarthestjgalaxiesjarejrecedingjfromjusjthejfastest.jAlljmatterjinjthejU
niversejwasjcontainedjinjajsinglejpoint,japproximatelyj13.8jbillionjyearsjago.jAtjtha
tjtime,jthejUniversejexplosivelyjcamejintojexistence.
2. Stars,jincludingjourjSun,jarejnuclear-
fusionjreactors.jForjmostjofjtheirjlifejhistoriesj(onjthejorderjofjbillionsjofjyears),jhydr
ogenjatomsjarejfusedjtogetherjtojformjhelium.jLaterjstagesjinjstellarjevolutionjincl
udejfusionjofjheliumjatomsjandjother,jheavierjelements;jultimately,jironjisjthejheav
iestjelementjthatjcanjbejproducedjthroughjfusionjreactionsjwithinjstars.
3. Afterjtheirjcyclesjofjfusionjarejcomplete,jlargejstarsjviolentlyjexplodej(formingjs
upernovas),jproducingjelementsjheavierjthanjironjandjleavingjbehindjajresiduej
ofjdiffusejnebulae,jwhichjmayjbejrecycledjtojformjajnewjstarjatjsomejfuturejpoin
t.
4. OurjSolarjSystemjisjapproximatelyj4.57jGaj(billionjyearsjold).jAlljeightjplanetsjrevol
vejaroundjthejSunjinjcoplanar,jellipticaljorbits.jAlljplanetsjorbitjinjthejsamejdirectio
nj(counterclockwise,jasjviewedjfromjabovejEarth’sjNorthjPole).jThesejfactsjimplyjs
imultaneousjplanetaryjformationjfromjajswirlingjnebulajsurroundingjthejSunj(thejsi
milaritiesjinjorbitsjwouldjthenjbejajnaturaljresultjofjconservationjofjangularjmomen
, tum).jThejplanetsjaccretedjfromjthisjnebulajthroughjgravitationaljattractionjandjha
phazardjcollisions.jPluto,jlongjconsideredjthej“ninthjplanet,”jhasjseenjitsjstatusjde
moted;jastronomersjnowjrecognizejeightjmajorjplanets.
5. Thejterrestrialjplanetsj(Mercury,jVenus,jEarth,jandjMars)jarejrelativelyjsmall,jdens
e,jandjrockyjworlds.jThejgiantjplanetsjarejpredominantlyjcomposedjofjthejlightjga
sesjhydrogenjandjheliumj(JupiterjandjSaturn)jorjicesj(UranusjandjNeptune);jtheyja
re
, muchjlargerjandjmuchjlessjdensejthanjthejterrestrialjplanets.
6. OurjMoonjisjthoughtjtojhavejoriginatedjfromjdebrisjaccumulatedjwhenjajprotoplan
etjcollidedjwithjEarthjapproximatelyj4.53jGa.
7. ThejEarthjSystemjisjsubdividedjintojthejatmospherej(gasesjandjaerosolsjthatjenvel
opjthejplanet),jhydrospherej(Earth’sjwater),jgeospherej(solidjEarth),jandjbiospher
ej(livingjthings).
8. Earthjisjchemicallyjdividedjintojajthin,jrockyjcrustjdominatedjbyjsilicatejminerals,jaj
thickjmantlejcomposedjmostlyjofjiron-jandjmagnesium-
richjsilicatesj(subjectjlocallyjtojpartialjmelting),jandjajthick,jmetallicjcorejmadejpri
marilyjofjironj(thejouterjportionjofjwhichjisjliquid).jStudentsjshouldjknowjhowjseism
icjwavesjtelljusjthatjthejouterjcorejmustjbejliquid.
9. Physically,jthejuppermostjlayersjofjEarthjarejthejrigidjlithospherej(crustjandjupper
mostjmantle)jandjthejasthenosphere,jwhichjisjweakerjandjflowsjplastically.jThej“p
lates”jofjplatejtectonicsjtheoryjarejdiscretejslabsjofjlithosphere,jwhichjmovejwithjr
espectjtojonejanotherjatopjthejasthenosphere.
SummaryjfromjthejText
ThejgeocentricjmodeljplacedjEarthjatjthejcenterjofjthejUniverse.jThejheliocentricj
modeljplacedjthejSunjatjthejcenter.
ThejEarthjisjonejofjeightjplanetsjorbitingjthejSun.jThejSolarjSystemjliesjonjthejouterj
edgejofjthejMilkyjWayjgalaxy.jThejUniversejcontainsjhundredsjofjbillionsjofjgalaxies.
MostjastronomersjagreejthatjthisjexpansionjbeganjafterjthejBigjBang,jajcataclysmi
cjexplosionjthatjoccurredjaboutj13.7jbillionjyearsjago.
Thejfirstjatomsj(hydrogenjandjhelium)jofjthejUniversejdevelopedjwithinjminutesjofj
thejBigjBang.jThesejatomsjformedjvastjgasjclouds,jcalledjnebulae.
OnlyjveryjsmalljatomsjformedjduringjBigjBangjnucleosynthesis.jThejEarth,jandjthe
j lifejformsjonjit,jcontainjelementsjthatjcouldjhavejbeenjproducedjonlyjduringjthejlifejcyc
le
Essentials of Geology 5th Edition
by Stephen Marshak All Chapters Covered
, CHAPTER 1 j
The Earth in Context
j j j
LearningjObjectives
1. StudentsjshouldjbejawarejofjthejBigjBangjtheory.jDistantjgalaxiesjarejalljmovingjaw
ayjfromjus.jThejfarthestjgalaxiesjarejrecedingjfromjusjthejfastest.jAlljmatterjinjthejU
niversejwasjcontainedjinjajsinglejpoint,japproximatelyj13.8jbillionjyearsjago.jAtjtha
tjtime,jthejUniversejexplosivelyjcamejintojexistence.
2. Stars,jincludingjourjSun,jarejnuclear-
fusionjreactors.jForjmostjofjtheirjlifejhistoriesj(onjthejorderjofjbillionsjofjyears),jhydr
ogenjatomsjarejfusedjtogetherjtojformjhelium.jLaterjstagesjinjstellarjevolutionjincl
udejfusionjofjheliumjatomsjandjother,jheavierjelements;jultimately,jironjisjthejheav
iestjelementjthatjcanjbejproducedjthroughjfusionjreactionsjwithinjstars.
3. Afterjtheirjcyclesjofjfusionjarejcomplete,jlargejstarsjviolentlyjexplodej(formingjs
upernovas),jproducingjelementsjheavierjthanjironjandjleavingjbehindjajresiduej
ofjdiffusejnebulae,jwhichjmayjbejrecycledjtojformjajnewjstarjatjsomejfuturejpoin
t.
4. OurjSolarjSystemjisjapproximatelyj4.57jGaj(billionjyearsjold).jAlljeightjplanetsjrevol
vejaroundjthejSunjinjcoplanar,jellipticaljorbits.jAlljplanetsjorbitjinjthejsamejdirectio
nj(counterclockwise,jasjviewedjfromjabovejEarth’sjNorthjPole).jThesejfactsjimplyjs
imultaneousjplanetaryjformationjfromjajswirlingjnebulajsurroundingjthejSunj(thejsi
milaritiesjinjorbitsjwouldjthenjbejajnaturaljresultjofjconservationjofjangularjmomen
, tum).jThejplanetsjaccretedjfromjthisjnebulajthroughjgravitationaljattractionjandjha
phazardjcollisions.jPluto,jlongjconsideredjthej“ninthjplanet,”jhasjseenjitsjstatusjde
moted;jastronomersjnowjrecognizejeightjmajorjplanets.
5. Thejterrestrialjplanetsj(Mercury,jVenus,jEarth,jandjMars)jarejrelativelyjsmall,jdens
e,jandjrockyjworlds.jThejgiantjplanetsjarejpredominantlyjcomposedjofjthejlightjga
sesjhydrogenjandjheliumj(JupiterjandjSaturn)jorjicesj(UranusjandjNeptune);jtheyja
re
, muchjlargerjandjmuchjlessjdensejthanjthejterrestrialjplanets.
6. OurjMoonjisjthoughtjtojhavejoriginatedjfromjdebrisjaccumulatedjwhenjajprotoplan
etjcollidedjwithjEarthjapproximatelyj4.53jGa.
7. ThejEarthjSystemjisjsubdividedjintojthejatmospherej(gasesjandjaerosolsjthatjenvel
opjthejplanet),jhydrospherej(Earth’sjwater),jgeospherej(solidjEarth),jandjbiospher
ej(livingjthings).
8. Earthjisjchemicallyjdividedjintojajthin,jrockyjcrustjdominatedjbyjsilicatejminerals,jaj
thickjmantlejcomposedjmostlyjofjiron-jandjmagnesium-
richjsilicatesj(subjectjlocallyjtojpartialjmelting),jandjajthick,jmetallicjcorejmadejpri
marilyjofjironj(thejouterjportionjofjwhichjisjliquid).jStudentsjshouldjknowjhowjseism
icjwavesjtelljusjthatjthejouterjcorejmustjbejliquid.
9. Physically,jthejuppermostjlayersjofjEarthjarejthejrigidjlithospherej(crustjandjupper
mostjmantle)jandjthejasthenosphere,jwhichjisjweakerjandjflowsjplastically.jThej“p
lates”jofjplatejtectonicsjtheoryjarejdiscretejslabsjofjlithosphere,jwhichjmovejwithjr
espectjtojonejanotherjatopjthejasthenosphere.
SummaryjfromjthejText
ThejgeocentricjmodeljplacedjEarthjatjthejcenterjofjthejUniverse.jThejheliocentricj
modeljplacedjthejSunjatjthejcenter.
ThejEarthjisjonejofjeightjplanetsjorbitingjthejSun.jThejSolarjSystemjliesjonjthejouterj
edgejofjthejMilkyjWayjgalaxy.jThejUniversejcontainsjhundredsjofjbillionsjofjgalaxies.
MostjastronomersjagreejthatjthisjexpansionjbeganjafterjthejBigjBang,jajcataclysmi
cjexplosionjthatjoccurredjaboutj13.7jbillionjyearsjago.
Thejfirstjatomsj(hydrogenjandjhelium)jofjthejUniversejdevelopedjwithinjminutesjofj
thejBigjBang.jThesejatomsjformedjvastjgasjclouds,jcalledjnebulae.
OnlyjveryjsmalljatomsjformedjduringjBigjBangjnucleosynthesis.jThejEarth,jandjthe
j lifejformsjonjit,jcontainjelementsjthatjcouldjhavejbeenjproducedjonlyjduringjthejlifejcyc
le
