2025年托福听力考试题库

2025年托福听力考试题库

Conversation1

Narrator:Listentoaconversationbetweenastudentandaprofessor.

Professor:Hi,Alex.YousentmeanemailaboutyourtermpaperproposalfortheEnvironmentalScienceclass.Comeonin.

Student:Thanks,ProfessorMiller.IwantedtorunmyideabyyoubeforeIstartedtheactualresearch.Iknowwe’resupposedtofocusonalocalecosystem,butI’mreallyinterestedinurbansustainability.

Professor:That’sfine,butremembertherequirement:youneedtoapplyecologicalprinciplestoaspecificproblem.Urbansustainabilityisabitbroad.Howwereyouplanningtonarrowitdown?

Student:Well,Iwasreadingabout"verticalforests"—youknow,thoseskyscraperscoveredintreesandshrubs,liketheoneinMilan.Iwasthinkingofanalyzingwhethertheycouldeffectivelyreplaceground-levelparksinadensecitylikeours.

Professor:That’safascinatingtopic.It’sdefinitelyrelevantto2025urbanplanningchallenges.However,analyzingwhethertheycanreplaceparksmightbetrickybecausetheyserveverydifferentfunctions.Averticalforestprovideshabitatforbirdsandinsects,andithelpswithairqualityandtemperatureregulation,butitdoesn'tofferthesamerecreationalspaceforpeopleorthesamesoilconnectivityforground-dwellingorganisms.

Student:Isee.SomaybeIshouldshiftthefocus.Insteadof"replacement,"maybeIshouldlookat"supplementation"?Like,howverticalforestscontributetobiodiversityinareaswherewesimplydon'thavespacefortraditionalparks?

Professor:Exactly.Thatsoundsmuchmorefeasible.Youcouldcomparethebiodiversityindex—speciesrichnessandabundance—ofaverticalforestversusatraditionalrooftopgarden.Weactuallyhavesomedatafromthenewbiologybuilding’sgreenroofthatyoucoulduseasabaseline.

Student:Thatwouldbeperfect.Iwasworriedaboutfindingprimarysources.

Professor:Icanpointyoutowardafewstudieson"greenfacades"versus"activelivingwalls."There’sadistinctdifferenceinmaintenanceandwaterusage,whichaffectstheecologicalfootprint.Youshouldfactorthatintoyourcost-benefitanalysis.

Student:Cost-benefit?Ithoughtitwasjustaboutbiology.

Professor:Itis,butinenvironmentalscience,ifasolutionconsumestoomuchenergyorwatertomaintaintheplants,itmightnotbeecologicallysustainableoverall.Forinstance,pumpingwaterup30storieshasacarboncost.

Student:Right,Ihadn'tconsideredtheenergyinput.I’llmakesuretoincludethatinthemethodologysection.

Professor:Good.Also,checkwiththecityplanningdepartmentdowntown.Theyjustfinishedareportonurbanheatislandsthatmighthavesometemperaturedatayoucancorrelatewithvegetationdensity.

Student:Thanks,Professor.I’llgetstartedontheliteraturereviewtoday.

Questions:

1.Whatisthemainpurposeofthestudent’svisit?

A.Toaskforanextensiononhistermpaper.

B.Togetfeedbackonaresearchtopic.

C.Toborrowdatafromtheprofessor'spersonalresearch.

D.Tocomplainaboutthelackofgreenspaceoncampus.

2.Whydoestheprofessoradvisethestudenttochangehisfocusfrom"replacing"parksto"supplementing"them?

A.Becauseverticalforestsaretooexpensivetobuild.

B.Becausethestudentlacksdataontraditionalparks.

C.Becauseverticalforestsandparksservedifferentecologicalandsocialfunctions.

D.Becausethecityhasalreadybannedtheconstructionofnewparks.

3.Whatdoestheprofessorimplyabout"activelivingwalls"?

A.Theyrequirelessmaintenancethangreenfacades.

B.Theymayhaveahigherecologicalfootprintduetoresourceusage.

C.Theyaretheonlysolutionforcoolingdownbuildings.

D.Theyareimpossibletoconstructinthelocalclimate.

4.Whatadditionalresourcedoestheprofessorrecommendthestudentconsult?

A.Areportfromthecityplanningdepartmentonurbanheatislands.

B.Astudyconductedbythearchitecturedepartment.

C.Thestudent'sprevioustextbookonurbangeography.

D.Aglobaldatabaseonskyscraperconstruction.

5.Whatcanbeinferredaboutthestudent?

A.Hehasalreadycompletedtheliteraturereview.

B.Heisprimarilyinterestedinthefinancialcostsofbuildingskyscrapers.

C.Heiswillingtoadjusthisresearchscopebasedonexpertadvice.

D.Hebelievesthattechnologyistheonlysolutiontoenvironmentalproblems.

Conversation2

Narrator:Listentoaconversationbetweenastudentandauniversityemployee.

Student:Hi,I’mlookingfortheticketofficefortheupcomingsymphonyperformance.Ithoughtitwasinthestudentunion,butthedoorsarelocked.

Employee:Oh,theboxofficemovedlastsemester.It’snowlocatedinthebasementoftheperformingartscenter,roomB012.Butactually,youdon’tneedtogothere.

Student:Idon’t?

Employee:No,forthestudentrushtickets,youcanreservethemonlinestartingatnoon.Sinceyou’reamusicmajor,yougetpriorityseating.

Student:That’sgreatnews.Iwasworriedaboutstandinginline.IstherealimitonhowmanyticketsIcanbuy?

Employee:YoucanpurchaseuptotwoticketsperstudentID.Oneforyourselfandoneforaguest.Butyouhavetopickthemupatthewill-callwindowatleastthirtyminutesbeforetheshowstarts.

Student:Okay,thatsoundseasyenough.Wait,Irememberlastyeartherewasafeeforusingacreditcard.Isthatstillthecase?

Employee:Thatpolicychangedthisyear.Thestudentgovernmentsubsidizedtheprocessingfees,soit’sfreeifyoupaywithyourstudentIDcard,whichlinkstoyourbursaraccount.Ifyouusearegularcreditcardorcash,thereisatwo-dollarservicecharge.

Student:I’lljustusemyIDthen.TheperformanceisonFriday,right?

Employee:Yes,FridayandSaturday.Butbecareful,theFridayshowisalmostsoldout.IfyouwantticketsforFriday,I’dloginrightnow.

Student:Ohwow.Ineedtotakemyyoungerbrother,he’svisitingfortheweekend.IguessI’lltryforSaturdaythen.

Employee:Saturdayhasplentyofseats.Also,justaheads-up:thereisapre-concerttalkbythecomposerat7:00PMinthelecturehall.It’sfreeforticketholders.

Student:Thatwouldbeperfectformyassignment.Ineedtowriteareviewontheuseofpercussionincontemporarysymphonies.

Employee:Thecomposerisknownforhisuniquepercussionensemble,sothattalkshouldbeveryhelpfulforyourpaper.

Questions:

1.Whydoesthestudentvisittheemployee?

A.Tofindthelocationoftheticketoffice.

B.Tocomplainaboutapolicychange.

C.Toaskaboutajobattheperformingartscenter.

D.Toreturnticketsforapreviousshow.

2.Accordingtotheemployee,howcanthestudentavoidaservicefee?

A.Bypayingwithcash.

B.ByusingastudentIDcard.

C.Bybuyingtheticketsattheboxoffice.

D.ByattendingtheSaturdayperformanceinsteadofFriday.

3.WhatdoestheemployeeimplyabouttheFridayperformance?

A.Ithasbeencancelled.

B.Itisarehearsalratherthanarealperformance.

C.Itisunlikelythatticketsarestillavailable.

D.Itisintendedforfacultymembersonly.

4.Whyisthestudentinterestedinthepre-concerttalk?

A.Hewantstomeetthecomposerpersonally.

B.Heneedsextracreditforhismusictheoryclass.

C.Heiswritingapaperonpercussioninsymphonies.

D.Hewantstoinvitehisprofessortotheevent.

5.Whatinformationdoestheemployeeprovideaboutthepre-concerttalk?

A.Itrequiresaseparateticket.

B.Ittakesplaceinthemainlecturehall.

C.Itisledbytheconductoroftheorchestra.

D.Itfocusesonthecomposer'suseofpercussion.

Lecture1:Biology

Narrator:ListentopartofalectureinaBiologyclass.TheprofessorisdiscussingAnimalBehavior.

Professor:Todaywe’regoingtocontinueourdiscussiononanimalcommunication,specificallyfocusingonaphenomenoncalled"honestsignaling."Now,intheanimalkingdom,individualsoftenneedtocommunicatetheirqualitytopotentialmatesorrivals.Thequestionis:howcanareceivertrustthatthesignalisaccurate?Whydon’tanimalscheat?

Student1:Becausetheycan’t?

Professor:Well,actually,theycouldtry.Butevolutionhasfavoredmechanismsthatmakecheatingtoocostly.Thisbringsustothe"HandicapPrinciple,"proposedbyAmotzZahavi.Theideaisthathigh-qualityindividualscanaffordtodisplay"handicaps"—traitsthatarecostlytoproduceormaintain—preciselybecausetheyarehighquality.Alow-qualityindividualsimplycouldn'tsurvivetheburdenofsuchatrait.

Let’slookattheclassicexample:thepeacock’stail.Thetailisheavy,itmakesflyingdifficult,anditattractspredators.Itisasignificanthandicap.Onlyaveryhealthy,strongpeacockcanaffordtocarryaroundsuchamagnificenttailandstillsurvive.Ifasick,weakpeacocktriedtogrowatailthatbig,itwouldlikelydiequicklyfrompredationorstarvation.Therefore,thetailisan"honestsignal"ofgeneticfitness.

Butit’snotjustaboutphysicalornaments.Itappliestobehaviortoo.Considerthe"stotting"behavioringazelles.Whenagazelledetectsapredator,likeacheetah,insteadofjustrunningaway,itmightjumpstraightupintotheairinastiff-leggedgait.Itlookssilly,right?Itslowsthegazelledownandwastesenergy.

Student2:Sowhydotheydoit?Toshowoff?

Professor:Inaway,yes.Theyaresignalingtothepredator.Themessageis:"Iamveryfastandfit.Don'tbotherchasingmebecauseyouwon'tcatchme."Thecheetah,lookingforaneasymeal,willseethegazellestottinganddecidetochaseadifferentonethatisn'tjumping.Thegazelleiseffectivelyturningthehuntintoacommunicationchannel.Thehandicaphereisthewastedenergyandthedelayinescape,butitpaysoffbydeterringthepredatorentirely.

Now,let’stalkaboutchemicalsignaling.Insomespeciesoflizards,thechemicalcompositionoftheirsecretionschangesbasedontheirhealth.Researchersfoundthatlizardsinfectedwithparasitesproduceddifferentscentprofilesthanhealthylizards.Thecosthereismetabolic.Producingthesespecificchemicalsrequiresenergyandresources.Aparasite-riddenlizardmightnothavetheresourcestoproducethe"healthy"scentprofile,orperhapstheparasitealtersthemetabolismdirectly,makingitphysiologicallyimpossibletofakethesignal.

Thisensuresthatwhenafemalelizardselectsamatebasedonscent,sheisgettinganhonestassessmentofhishealth.Ifsignalscouldbefakedeasily,thewholesystemwouldcollapse.Femaleswouldevolvetoignorethesignals,andmaleswouldstopproducingthem.Thestabilityofthesystemreliesonthecost.

So,tosummarize:honestsignalsarethosethatarereliablebecausetheyaretooexpensiveforlow-qualityindividualstoproduceormaintain.Whetherit’saheavytail,ariskyjump,oracomplexchemicalsignature,thecostensuresthehonesty.

Questions:

1.Whatisthemaintopicofthelecture?

A.Theevolutionofphysicalornamentsinbirds.

B.Thereasonswhyanimalsrarelycommunicatewitheachother.

C.TheconceptofhonestsignalingandtheHandicapPrinciple.

D.Thehuntingstrategiesofcheetahsandgazelles.

2.Accordingtotheprofessor,whyisthepeacock’stailconsideredan"honestsignal"?

A.Itisbrightlycoloredandeasytosee.

B.Itisatraitthatonlyahealthy,strongindividualcansustain.

C.Itisusedtowarnoffpredatorsratherthanattractmates.

D.Itisgeneticallyidenticalinallpeacocks.

3.Howdoestheprofessorexplainthefunctionof"stotting"ingazelles?

A.Ithelpsthegazellejumpoverobstaclestoescape.

B.Itconfusesthepredatorbycreatingavisualillusion.

C.Itsignalstothepredatorthatthegazelleisfitandhardtocatch.

D.Itisaformofplaybehaviorpracticedbyyounggazelles.

4.Whatpointdoestheprofessormakeaboutchemicalsignalinginlizards?

A.Lizardsusechemicalsignalstomarktheirterritoryboundaries.

B.Chemicalsignalsareunreliablebecauseparasitescanmimicthem.

C.Itismetabolicallydifficultforunhealthylizardstofakeahealthyscent.

D.Femalelizardsprefermateswithnoscentatall.

5.Whydoestheprofessormentionthatthesystemwouldcollapseifsignalscouldbefaked?

A.Toillustratetheevolutionaryarmsracebetweenmalesandfemales.

B.Toemphasizetheimportanceofcostinmaintaininghonestsignals.

C.Toprovethatanimalsarecapableofcomplexreasoning.

D.Toshowthatpredatorsarethedrivingforcebehindsignalevolution.

Lecture2:ArtHistory

Narrator:ListentopartofalectureinanArtHistoryclass.

Professor:We’vespentthelastfewweeksdiscussingtheRenaissance,focusingonthelinearperspectiveandtheidealizationofthehumanform.Today,we’removingforwardintimetothelate19thcentury,toamovementthatcompletelyshatteredthoserules:Impressionism.

Now,whenwethinkofImpressionism,weoftenthinkofsunnylandscapesandoutdoorscenes.ButtherootsofthemovementlieheavilyinthechangeshappeninginParisatthetime.Specifically,therenovationofParisbyBaronHaussmann.Thecitywastransformedwithwideboulevards,newparks,and,crucially,gaslighting.

Beforethisrenovation,Pariswasamedievalmazeofdark,narrowstreets.ButHaussmann’schangescreatedanewurbanculture:thecafeculture.Peoplesocializedoutdoors;theystrolledalongtheboulevards.Thisaccessibilityofpubliclifegaveartistsanewsubjectmatter.Theydidn'tjustwanttopaintgodsandhistoricalbattlesanymore;theywantedtopaintmodernlife.

However,paintingmodernlifepresentedatechnicalchallenge.Traditionalacademicpaintingtookplaceinthestudio.Itwasslow,deliberate,anduseddark,varnishedcolors.ButtheImpressionists—Monet,Renoir,Pissarro—wantedtocapturethefleetingmoment.Theywantedtopainttheimpressionofascene,thelight,themovement.

Todothis,theyhadtoleavethestudio.Thisisknownas"enpleinair"painting.Butyoucan'tcarryahugeeaselandtubesofslow-dryingoilpainteasily.So,technologicalinnovationshelpedheretoo.Theinventionoftinpainttubesmadepaintportableandpreserveditfromdryingout.ThisallowedartiststogotothebanksoftheSeineorabusycafeterraceandpaintonthespot.

Butthemostradicalchangewasintheiruseofcolorandlight.TheAcadémietaughtthatshadowswereblackorbrown.ButifyoulookatanImpressionistpainting,likeMonet’s"Impression,Sunrise,"theshadowsareblue,purple,ororange.Why?BecausetheImpressionistsunderstoodthatshadowsarenottheabsenceoflight;theyaresimplylightofadifferentcolorandtemperature,oftenreflectingtheskyabove.

Theyalsousedatechniquecalled"brokencolor."Insteadofmixinggreenonthepalettetopaintgrass,theymightplacedotsofblueandyellownexttoeachotheronthecanvas.Atadistance,theviewer'seyeblendsthemtocreategreen,butupclose,itvibrateswithenergy.Thismimicsthewaytheeyeactuallyperceiveslightintherealworld,whichisneverasolid,flatblockofcolor.

Criticsatthetimehatedthis.Theysaidtheworklookedunfinished,likesketches.Onecritic,LouisLeroy,famouslyusedthetitleofMonet’spaintingtomockthegroup,callingthem"TheImpressionists."Hemeantitasaninsult,implyingtheycouldn'tfinishapaintingproperly.Butthenamestuck.

So,Impressionismwasn'tjustastyle;itwasanewwayofseeing.ItcombinedthenewleisureclassofmodernPariswithscientifictheoriesoflightandportabletechnologytocreateoneofthemostpopularartmovementsinhistory.

Questions:

1.WhatdoestheprofessoridentifyasamajorinfluenceonthesubjectmatterofImpressionistart?

A.ThereconstructionofParisunderBaronHaussmann.

B.Theinventionofphotography.

C.ThereturntoclassicalGreekandRomanideals.

D.ThepoliticalupheavalsoftheFrenchRevolution.

2.Accordingtothelecture,howdidtherenovationofParisaffecttheartists?

A.Itdestroyedtheoldstudioswheretheyusedtowork.

B.Itcreatedwideboulevardsandpublicspacesthatbecamenewsubjectsforpainting.

C.Itmadethecitytooexpensiveforartiststolivein.

D.Itforcedartiststomovetothecountrysidetofindinspiration.

3.Whydoestheprofessormentiontinpainttubes?

A.Toexplainwhytraditionalacademicpaintingdeclinedinpopularity.

B.Toshowhowtechnologyenabledartiststopaintoutdoors.

C.Toillustratethehighcostofartsuppliesinthe19thcentury.

D.TopointoutthatImpressionistspreferredcheapmaterials.

4.HowdoestheprofessordescribetheImpressionists'useofshadows?

A.Theyavoidedpaintingshadowstokeepthepaintingsbright.

B.Theyusedblackpainttocreatesharpcontrasts.

C.Theyusedcolorslikeblueandpurpletorepresentreflectedlight.

D.Theymixedgraywithwhitetosoftentheedges.

5.Whatisthe"brokencolor"technique?

A.Applyingpaintinthick,heavylayerstoshowtexture.

B.Placingdistinctcolorsnexttoeachothersotheeyeblendsthem.

C.Usingapaletteknifetoscrapepaintoffthecanvas.

D.Paintingquicklywithoutwaitingforlayerstodry.

6.Whatwasthecritics'initialreactiontoImpressionism?

A.Theypraisedtheartistsfortheirscientificaccuracy.

B.Theyboughtthepaintingsforhighpricesimmediately.

C.Theyfeltthepaintingslookedunfinishedandsketch-like.

D.Theywereconfusedbythelackofhistoricalsubjects.

Lecture3:Astronomy

Narrator:ListentopartofalectureinanAstronomyclass.

Professor:Today,Iwanttodiscusshowwedeterminetheageoftheuniverse.Thisisoneofthemostfundamentalquestionsincosmology.Foralongtime,wedidn'tevenknowiftheuniversehadabeginning;manyscientiststhoughtitwasstaticandeternal.ButthatchangedwithEdwinHubble’sobservationsinthe20thcentury,whichledtotheBigBangtheory.

Iftheuniverseisexpanding,asHubbleshowed,thenitmusthavebeensmalleranddenserinthepast.Ifwerewindtheexpansionallthewayback,wearriveatasingularpointofinfinitedensity—asingularity.Thetimeittakestogetfromthatpointtowherewearenowistheageoftheuniverse.

Tocalculatethis,weneedtoknowtwothings:howfarawaygalaxiesareandhowfasttheyaremovingawayfromus.ThisrelationshipisknownasHubble’sLaw.Thespeedofrecessionisproportionaltothedistance.TheconstantofproportionalityistheHubbleConstant,denotedas.

Mathematically,wecanexpresstheageoftheuniverse,t,roughlyastheinverseoftheHubbleConstant.So,t≈.However,thisisasimplification.Itassumestheexpansionhasbeenconstantthroughouthistory.Butweknowthathasn'tbeenthecase.Gravityactstoslowtheexpansiondown,andmorerecently,wediscoveredamysteriousforcecalled"darkenergy"thatisacceleratingtheexpansion.

So,togetanaccurateage,wehavetocreateamodeloftheuniverse'scomposition.Howmuchmatteristhere?Howmuchdarkenergy?Theseparametersaffecttheexpansionrateovertime.Currentmodels,basedondatafromsatelliteslikethePlancksatellite,suggesttheuniverseisabout13.8billionyearsold.

Butwedon'tjustrelyononemethod.Welookfortheoldeststarswecanfind.Wecandeterminetheageofastarclusterbylookingatits"mainsequenceturnoff"ontheHertzsprung-Russelldiagram.Starsburntheirfuelatpredictablerates.Massivestarsburnfastanddieyoung;smallerstarsburnslowlyandlivelong.

Inaclusterofstarsbornatthesametime,themostmassiveoneswillturnoffthemainsequencefirst.Bylookingatwhichstarsarestillonthemainsequenceandwhichhaveevolvedintoredgiants,wecancalculatethecluster'sage.Theoldestglobularclustersinourgalaxyareabout12to13billionyearsold.Thisfitsperfectlywiththe13.8billionyearfigurefromtheexpansionrate;theuniversemustbeolderthantheoldestthingsinit.

Thereisathirdmethod,thoughit’slessprecise:lookingatthechemicalcompositionofstars.Theearlyuniverseonlycontainedhydrogen,helium,andtraceamountsoflithium.Heavierelements—carbon,oxygen,iron—wereforgedinsidestarsandscatteredbysupernovae.So,ifwefindastarwithverylowmetallicity,itmusthaveformedveryearlyintheuniverse'shistory,beforewehadgenerationsofstarspollutingtheinterstellarmedium.These"PopulationIII"stars—orrather,thelow-metallicitystarsweseenow—giveusalowerlimitfortheage.

Bycombiningtheexpansionrate(cosmology),theagesofstarclusters(stellarevolution),andchemicalabundances(nucleosynthesis),wegetaremarkablyconsistentpictureofauniversethatisroughly13.8billionyearsold.

Questions:

1.Accordingtotheprofessor,whatdidEdwinHubble’sobservationsdemonstrate?

A.Thattheuniverseisstaticandunchanging.

B.Thattheuniverseisexpanding.

C.ThattheMilkyWayistheonlygalaxyinexistence.

D.Thatdarkenergyisthedominantforceintheuniverse.

2.HowistheHubbleConstantusedtoestimatetheageoftheuniverse?

A.Bymeasuringthebrightnessofdistantsupernovae.

B.Bycalculatingtheinverseoftheexpansionrate.

C.Bycountingthenumberofgalaxiesinaspecificsector.

D.Byanalyzingthespectrumoflightfromquasars.

3.Whydoestheprofessormentiongravityanddarkenergy?

A.ToexplainwhythesimplecalculationusingtheHubbleConstantisnotentirelyaccurate.

B.Toprovethattheuniversewilleventuallycollapsebackonitself.

C.ToshowthattheHubbleConstantchangesvaluedependingontheseason.

D.Toarguethattheuniverseismuchyoungerthanpreviouslythought.

4.Whatisthe"mainsequenceturnoff"methodusedfor?

A.Todeterminethedistancetoastarcluster.

B.Tocalculatethechemicalcompositionofastar.

C.Toestimatetheageofaclusterofstars.

D.ToidentifyblackholesintheMilkyWay.

5.Whatcanbeinferredaboutastarwithverylowmetallicity?

A.Itisaveryyoungstarthatjustformedrecently.

B.Itislikelylocatedinthecenterofthegalaxy.

C.Itformedearlyintheuniverse'shistory.

D.Itcontainslargeamountsofdarkmatter.

6.Whatistheprofessor'sattitudetowardthecurrentestimatesoftheuniverse'sage?

A.Heisskepticalbecausethemethodscontradicteachother.

B.Heisconfidentbecausedifferentmethodsyieldconsistentresults.

C.Heisconcernedthatthemarginoferroristoolarge.

D.Hebelievestheuniverseisactuallymucholderthan13.8billionyears.

Lecture4:Geology

Narrator:ListentopartofalectureinaGeologyclass.

Professor:We’vebeentalkingaboutplatetectonics,thetheorythattheEarth'slithosphereisdividedintoplatesthatmove.Butwhatdrivesthismovement?It’snotliketheplateshaveenginesattachedtothem.Thedrivingforceisactuallyhappeningdeepbeneathourfeet,inthemantle.

ThemantleisthelayeroftheEarthbetweenthecrustandthecore.It’ssolidrock,butovergeologicaltimescales,itbehaveslikeahighlyviscousfluid—thinkofitasanincrediblythick,slow-movingasphalt.Thispropertyiscalled"plasticity."TheheatfromtheEarth'scorecausesthemantletoheatup.Hotmaterialislessdensethancoldmaterial,sothehotrocknearthecorerisestowardthecrust.

Asitrises,itcoolsdown.Onceitreachesthelithosphere,itlosesheattothesurface,becomesdenser,andeventuallysinksbackdown.Thiscircularmotioniscalleda"convectioncurrent."Youcanseethisinapotofboilingsoup,thoughinthemantle,ithappensmillionsoftimesslower.

Theseconvectioncurrentsaretheengineofplatetectonics.Thefrictionbetweenthemovingmantleandthelithospheredragstheplatesalong.Therearetwomaintypesofplateboundariesassociatedwiththismovement:divergentandconvergent.

Atdivergentboundaries,platesmoveapart.Thishappenswhereconvectioncurrentsarerising.Thehotmantlematerialupwells,meltsduetopressurerelease,andformsnewcrust.Thisiswhat’shappeningattheMid-AtlanticRidge.Astheplatesmoveapart,magmafillsthegap,cools,andbecomessolidrock.

Atconvergentboundaries,platesmovetogether.Thisoccurswhereconvectioncurrentsaresinking.Here,thedenseoceaniccrustdivesbeneaththelightercontinentalcrustinaprocesscalled"subduction."Astheslabsinks,itmeltsandformsvolcanoes.Thisiswhyweseethe"RingofFire"aroundthePacificOcean.

However,there’sathirdtypeofboundarythatdoesn'tfitneatlyintothesimple"conveyorbelt"modelofconvection:transformboundaries.Here,platesslidepasteachotherhorizontally.TheSanAndreasFaultinCaliforniaisafamousexample.Convectioncurrentsdon'tdirectlydrivethissliding;rather,it’saresultoftheplatesmovingindifferentdirectionsonacurvedsurface.Thecrustgetsfracturedbecausetheplatescan'tslidesmoothlyduetofriction.

Recentresearchsuggeststhatthemantleisn'tjustonesimplelayerofconvection.Wehaveevidencefromseismictomography—essentiallyCATscansoftheEarth—thatthereare"superplumes."Thesearemassiveupwellingsofhotmaterialthatrisefromtheverybottomofthemantle,nearthecore-mantleboundary.TheHawaiianIslandsarethoughttobecausedbyastationaryhotspotinthemiddleofthePacificPlate,createdbysuchasuperplume.Astheplatemovesoverthishotspot,itleavesatrailofislands.

So,whilethebasicprincipleisconvection,therealityisacomplex3Dsystemofrisingandsinkingplumesinteractingwiththerigidplatesabove.

Questions:

1.Whatisthemaintopicofthelecture?

A.ThechemicalcompositionoftheEarth'score.

B.Theroleofmantleconvectionindrivingplatetectonics.

C.Thehistoryofthetheoryofcontinentaldrift.

D.Thedifferencesbetweenoceanicandcontinentalcrust.

2.Accordingtotheprofessor,whydoesrockinthemantlerise?

A.Becauseitisliquidandflowsupward.

B.Becauseitislessdensethanthesurroundingcoolerrock.

C.Becausepressurefromthecrustpushesitdown.

D.Becauseitcontainsironwhichisattractedtothepoles.

3.Howdoestheprofessorexplaintheconceptofplasticity?

A.Bycomparingthemantletoapotofboilingsoup.

B.Bydescribingitasasolidthatflowslikeaviscousfluidovertime.

C.Bystatingthatthemantleismadeofplasticmaterials.

D.ByshowingadiagramoftheEarth'slayers.

4.Whatgeologicalfeatureisformedatadivergentboundary?

A.Adeepoceantrench.

B.Amountainrange.

C.Newcrustfromupwellingmagma.

D.Atransformfault.

5.WhydoestheprofessormentiontheSanAndreasFault?

A.Asanexampleofaconvergentboundary.

B.Toillustratetheconceptofahotspot.

C.Asan