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1、2014高考英語(yǔ)沖刺閱讀理解專(zhuān)項(xiàng)50-12ARecognizedasthelargestdesertintheworld,theSahararunsacrossNorthAfrica,Coveringover3millionsquaremilesfromtheAtlanticCoasttotheNileRiverValley.Exceptforanoccasionaloasis(綠洲),thisvastlandismainlymadeupofsand,stones,andwornoutmountains.Theburningsun
2、causesdaytimetemperaturestoriseto70degreesintheshade,anddayswithoutraincommonlylastforyears.PaintingsfoundonthewallsofcavesintheSaharaDesertsuggestthatafewthousandyearsago,largequantitiesofplantsgrewthereandcoveredthedesertfloor.Manycuriousandunusualinsects,birdsandan
3、imalsgotenoughfoodthatallowedthemtogrowandreproduce.Atthattime,hugeriversystemsandmanyoasessupportedgrowingcommunities(社團(tuán)，社區(qū))wherealargenumberofpeoplelived.Researchscientistsbelievethatthelandbecameadesertforseveralreasons.Forcenturiespeopletherehavewanderedfromplacet
4、oplaceinsearchoffood,waterandgrazing(吃草)landfortheiranimals.Thesepeoplehavealwaysconsideredthenumberofanimalstheyhaveasasignofwealth.Itisconsideredmoreimportanttohave100sickandstarvinganimalsthan15healthyones.Thelargeherds(群)havebeenallowedtogofreelyandgrazeondesertpl
5、antsandgrass.Overtime,largesectionsoflandhavebeenleftuncovered.Inadditiontoallowingovergrazing,thesepeoplecutdownwhatevertreestheycouldfindandusedthemforfirewood.Thesandwasunabletoholdontothegreatheatoftheday,sonighttingtemperaturesoftendropbelowfreezingandnothingwasl
6、efttoholdthesoiltogether.Scientistshavebeenstudyingdifferentwaystobringbackthegreendesert.Throughresearchandexperiments,theyhopetobeabletoproduceplantsthatwillonceagainsupportthelifethere.Hugeholesfilledwithmuchwaterlieunderthedesertsurface.Scientistsbelievethisrainwa
7、tersimplyflewdownthroughthesandoverhundredsofyearsandcollectedinthebig,rockyholdingtanks.Bymakinguseofthesun’spower,scientistsintheSaharahavemadeexperimentsinwhichtheygothugeamountofelectricity.Thiselectricitywasthenusedtooperatedrillingmachinesandpumpstopulltherainwa
8、terfromtheundergroundtanks.Bydrillingtheholeonemiledeepintothefloorofthedesert,onemachinewasabletorecovermorethan80gallonsof
