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Passage3
EveryonehasheardoftheSanAndreasfault(断层),whichconstantlythreatensCaliforniaandtheWestCoastwithearthquakes.ButhowmanypeopleknowabouttheequallyseriousNewMadridfaultinMissouri?
BetweenDecemberof1811andFebruaryof1812,threemajorearthquakesoccurred,allcenteredaroundthetownofNewMadrid,Missouri,ontheMississippiRiver.Propertydamagewassevere.Buildingsintheareawerealmostdestroyed.Wholeforestsfellatonce,andhugecracksopenedintheground,allowingsmellofsulfur(硫磺)tofilterupward.
TheMississippiRiveritselfcompletelychangedcharacter,developingsuddenrapidsandwhirlpools.Severaltimesitchangeditscourse,andonce,accordingtosomeobservers,itactuallyappearedtorunbackwards.FewpeoplewerekilledintheNewMaridearthquakes,probablysimplybecausefewpeoplelivedintheareain1811;buttheseverityoftheearthquakesareshownbythefactthattheshockwavesrangbellsinchurchtowersinCharleston,SouthCarolina,onthecoast.BuildingsshookinNewYorkCity,andclockswerstoppedinWashington,D.C.ScientistsnowknowthatAmerica'stwomajorfaultsareessentiallydifferent.TheSanAndreasisahorizontalboundarybetweentwomajorlandmassesthatareslowlymovinginoppositedirections.Californiaearthquakesresultwhenthemovementofthesetwomassessuddenlylurches(倾斜)forward.
TheNewMadridfault,ontheotherhand,isaverticalfault;atsomepoints,possiblyhundredsofmillionsofyearsago,rockwaspusheduptowardthesurface,probablybyvolcanoesunderthesurface.Suddenly,thevolcanoescooledandtherockcollapsed,leavinghugecracks.Evennow,therockcontinuestosettledownwards,andsuddensinkingmotionstrigger(触发)earthquakesintheregion.Thefaultitself,alargecrackinthislayerofrock,withdozensofothercracksthatsplitofffromit,extendsfromnortheastArkansasthroughMissouriandintosouthernlllinois.
ScientistswhohavestudiedtheNewMadridfaultsaytherehavebeennumeroussmallerquakesintheareasince1811;thesesmallerquakesindicatethatlargeronesareprobablycoming,butthescientistssayhavenomethodofpredictingwhenalargeearthquakewilloccur.
1.Thispassageismainlyabout.
A)theNewMadridfaultinMissouri
B)theSanAndreasandtheNewMadridfaults
C)thecausesoffaults
D)currentscientificknowledgeaboutfaults
2.TheNewMadridfaultis.
A)ahorizontalfault
B)averticalfault
C)amoreseriousfaultthantheSanAndreasfault
D)responsibleforformingtheMississippiRiver
3.Wemayconcludefromthepassagethat.
A)itisprobablyasdangeroustoliveinMissouriasinCalifornia
B)theNewMadridfaultwilleventuallydevelopamountainrangeinMissouri
C)Californiawillbecomeanislandinfuture
D)AbigearthquakewilloccurtoCaliforniasoon
4.Thispassageimpliesthat.
A)horizontalfaultsaremoredangerousthanverticalfaults.
B)Verticalfaultsaremoredangerousthanhorizontalfaults
C)Earthquakesoccuronlyaroundfaultareas
D)Californiawillbreakintopiecesbyaneventualearthquake
5.Asusedinthefirstsentenceofthefourthparagraph,thewordessentiallymeans.
A)greatly
C)basically
B)extremely
D)necessarily
Answer
1.B2.B3.A4.C5.C |
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