tpo25阅读全三篇含答案托福真题.docx

tpo25阅读全三篇含答案托福真题.docx

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tpo25阅读全三篇含答案托福真题

ThesurfaceofMars

ThesurfaceofMarsshowsawiderangeofgeologicfeatures,includinghugevolcanoes-thelargestknowninthesolarsystem-andextensiveimpactcratering.ThreeverylargevolcanoesarefoundontheTharsisbulge,anenormousgeologicareanearMars’sequator.NorthwestofTharsisisthelargestvolcanoofall:

OlympusMons,withaheightof25kilometersandmeasuringsome700kilometersindiameteratitsbase.ThethreelargevolcanoesontheTharsisbulgearealittlesmaller-a“mere”18kilometershigh.

NoneofthesevolcanoeswasformedasaresultofcollisionsbetweenplatesoftheMartiancrust-thereisnoplatemotiononMars.Instead,theyareshieldvolcanoes-volcanoeswithbroad,slopingslidesformedbymoltenrock.AllfourshowdistinctivelavachannelsandotherflowfeaturessimilartothosefoundonshieldvolcanoesonEarth.ImagesoftheMartiansurfacerevealmanyhundredsofvolcanoes.MostofthelargestvolcanoesareassociatedwiththeTharsisbulge,butmanysmalleronesarefoundinthenorthernplains.

ThegreatheightofMartianvolcanoesisadirectconsequenceoftheplanet’slowsurfacegravity.Aslavaflowsandspreadstoformashieldvolcano,thevolcano’seventualheightdependsonthenewmountain’sabilitytosupportitsownweight.Thelowerthegravity,thelessertheweightandthegreatertheheightofthemountain.ItisnoaccidentthatMaxwellMonsonVenusandtheHawaiianshieldvolcanoesonEarthrisetoaboutthesameheight（about10kilometers）abovetheirrespectivebases-EarthandVenushavesimilarsurfacegravity.Mars’ssurfacegravityisonly40percentthatofEarth,sovolcanoesriseroughly2.5timesashigh.AretheMartianshieldvolcanoesstillactive?

Scientistshavenodirectevidenceforrecentorongoingeruptions,butifthesevolcanoeswereactiveasrecentlyas100millionyearsago（anestimateofthetimeoflasteruptionbasedontheextentofimpactcrateringontheirslopes）,someofthemmaystillbeatleastintermittentlyactive.Millionsofyears,though,maypassbetweeneruptions.

AnotherprominentfeatureofMars’ssurfaceiscratering.TheMarinerspacecraftfoundthatthesurfaceofMars,aswellasthatofitstwomoons,ispittedwithimpactcratersformedbymeteoroidsfallinginfromspace.AsonourMoon,thesmallercratersareoftenfilledwithsurfacematter-mostlydust-confirmingthatMarsisadrydesertworld.However,Martiancratersgetfilledinconsiderablyfasterthantheirlunarcounterparts.OntheMoon,ancientcraterslessthan100metersacross（correspondingtodepthsofabout20meters）havebeenobliterated,primarilybymeteoriticerosion.OnMars,therearerelativelyfewcraterslessthan5kilometersindiameter.TheMartianatmosphereisanefficienterosiveagent,withMartianwindstransportingdustfromplacetoplaceanderasingsurfacefeaturesmuchfasterthanmeteoriticimpactsalonecanobliteratethem.

AsontheMoon,theextentoflargeimpactcratering（i.e.craterstoobigtohavebeenfilledinbyerosionsincetheywereformed）servesasanageindicatorfortheMartiansurface.AgeestimatesrangingfromfourbillionyearsforMars’ssouthernhighlandstoafewhundredmillionyearsintheyoungestvolcanicareaswereobtainedinthisway.

ThedetailedappearanceofMartianimpactcratersprovidesanimportantpieceofinformationaboutconditionsjustbelowtheplanet’ssurface.Martiancratersaresurroundedbyejecta（debrisformedasaresultofanimpact）thatlooksquitedifferentfromitslunarcounterparts.AcomparisonoftheCopernicuscraterontheMoonwiththe（fairlytypical）craterYutyonMarsdemonstratesthedifferences.Theejectasurroundingthelunarcraterisjustwhatonewouldexpectfromanexplosionejectingalargevolumeofdust,soil,andboulders.■However,theejectaonMarsgivesthedistinctimpressionofaliquidthathassplashedorflowedoutofcrater.■Geologiststhinkthatthisfluidizedejectacraterindicatesthatalayerofpermafrost,orwaterice,liesjustafewmetersunderthesurface.■Explosiveimpactsheatedandliquefiedtheice,resultinginthefluidappearanceoftheejecta.■

Q1Theword“enormous”inthepassageisclosestinmeaningto

A.Important

B.Extremelylarge

C.Highlyunusual

D.Active

Q2Accordingtoparagraph1,OlympusMonsdiffersfromvolcanoesontheTharsisbulgeinthatOlympusMons

A.Hasmorecomplexgeologicfeatures

B.Showslessimpactcratering

C.Istaller

D.Wasformedatalatertime

Paragraph1

Q3Theword“distinctive”inthepassageisclosestinmeaningto

A.Deep

B.Complex

C.Characteristic

D.Ancient

Q4Accordingtoparagraphs1and2,whichofthefollowingisNOTtrueoftheshieldvolcanoesontheTharsisbulge?

A.Theyhavebroad,slopingsides.

B.TheyaresmallerthanthelargestvolcanoonMars.

C.TheyhavechannelsthatresemblethelavachannelsofvolcanoesonEarth.

D.Theyareover25kilometerstall.

Paragraph1and2

Q5Theword“roughly”inthepassageisclosestinmeaningto

A.Typically

B.Frequently

C.Actually

D.Approximately

Q6Inparagraph3,whydoestheauthorcompareMaxwellMonsonVenustotheHawaiianshieldvolcanoesonEarth?

A.Tohelpexplaintherelationshipbetweensurfacegravityandvolcanoheight

B.ToexplainwhyMars’ssurfacegravityisonly40percentofEarth’s

C.TopointoutdifferencesbetweenthesurfacegravityofEarthandthesurfacegravityofVenus

D.Toarguethattherearemoresimilaritiesthandifferencesbetweenvolcanoesondifferentplanets

Paragraph3

Q7Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?

Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.

A.Althoughdirectevidenceofrecenteruptionsislacking,scientistsbelievethatthesevolcanoeswereactiveasrecentlyas100millionyearsago.

B.Scientistsestimatethatvolcanoesactivemorerecentlythan100yearsagowillstillhaveextensiveimpactcrateringontheirslopes.

C.If,assomeevidencesuggests,thesevolcanoeseruptedasrecentlyas100millionyearsago,theymaycontinuetobeintermittentlyactive.

D.Althoughthesevolcanoeswereactiveasrecentlyas100millionyearsago,thereisnodirectevidenceofrecentorongoingeruptions.

Q8Theword“considerably”inthepassageisclosestinmeaningto

A.Frequently

B.Significantly

C.Clearly

D.Surprisingly

Q9Accordingtoparagraph4,whatisdemonstratedbythefactthatcratersfillinmuchfasteronMarsthanontheMoon?

A.ErosionfrommeteoriticimpactstakesplacemorequicklyonMarsthanontheMoon.

B.ThereismoredustonMarsthanontheMoon.

C.ThesurfaceofMarsisadrydesert.

D.WindisapowerfulerodingforceonMars.

Paragraph4

Q10Inparagraph4,whydoestheauthorpointoutthatMarshasfewancientcratersthatarelessthan5kilometersindiameter?

A.ToexplainwhyscientistsbelievethatthesurfacematterfillingMartiancratersismostlydust

B.ToexplainwhyscientistsbelievethattheimpactcratersonMarswerecreatedbymeteoroids

C.TosupporttheclaimthattheMartianatmosphereisanefficienterosiveagent

D.ToarguethatMarsexperiencedfewerancientimpactsthantheMoondid

Paragraph4

Q11Accordingtoparagraph5,whathavescientistsbeenabletodeterminefromstudiesoflargeimpactcrateringonMars?

A.SomeMartianvolcanoesaremucholderthanwasoncethought.

B.TheageofMars’ssurfacecanvaryfromareatoarea.

C.Largeimpactcratersarenotreliableindicatorsofageinareaswithhighvolcanicactivity.

D.SomeareasoftheMartiansurfaceappeartobeolderthantheyactuallyare.

Paragraph5

Q12Accordingtoparagraph6,theejectaofMars’scraterYutydiffersfromtheejectaoftheMoon’sCopernicuscraterinthattheejectaoftheYutycrater

A.Hasnowbecomepartofapermafrostlayer

B.Containsalargevolumeofdust,soilandboulders

C.Suggeststhatliquidoncecameoutofthesurfaceatthecratersite

D.Wasthrownacomparativelylongdistancefromthecenterofthecrater

Paragraph6ismarkedwithanarrow>

Q13Lookatthefoursquares【■】thatindicatewherethefollowingsentencecouldbeaddedtothepassage.

ThissurfacefeaturehasledtospeculationaboutwhatmaylieunderMars’ssurface.

Wherewouldthesentencebestfit?

Clickonasquaretoaddthesentencetothepassage.

Q14Directions:

Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

Dragyouranswerchoicestothespaceswheretheybelong.Toremoveananswerchoice,clickonit.Toreviewthepassage,clickVIEWNEXT.VolcanoesandimpactcratersaremajorfeaturesofMartiangeology.

A.PlatemotiononMars,onceconsideredtohaveplayednoroleinshapingtheplanet’ssurface,isnowseenasbeingdirectlyassociatedwiththeplanet’searliestvolcanoes.

B.Marshasshieldvolcanoes,someofwhichareextremelytallbecauseoftheplanet’slowsurfacegravity.

C.AlthoughtheerosivepoweroftheMartianatmosphereensuresthatMarshasfewercratersthantheMoondoes,impactcratersareprominentonMars’ssurface.

D.ScientistscannotyetreliablyestimatetheageoftheMartiansurfacebecausetherehasbeentoomucherosionofit.

E.ScientistshavebeensurprisedtodiscoverthatconditionsjustbelowthesurfaceofMarsareverysimilartoconditionsjustbelowthesurfaceoftheMoon

F.Studiesofcratere