TPO-7 Reading 1 阅读译文

The GeologicHistory of the Mediterranean地中海向地质历史In1970geologists Kenneth J.Hsu andWilliam B.F.Ryan werecollecting researchdatawhile aboard the oceanographicresearch vesselGlomar Challenger.An objectiveofthis particularcruise wasto investigatethe floorof the Mediterranean andto resolvequestionsabout itsgeologic history.One questionwas relatedto evidencethat theinvertebratefauna animalswithout spinesof theMediterranean hadchanged abruptlyabout6million yearsago.Most of the olderorganisms werenearly wipedout,although afewhardy speciessurvived.A fewmanaged tomigrate into the Atlantic.Somewhat later,the migrantsreturned,bringing newspecies withthem.Why didthe nearextinction andmigrationsoccur1970年，地理学家KennethJ.Hsu和William B.F.Ryan在海洋调查船GlomarChallenger号上收集调研资料这次特别巡航的一个目的是调查地中海的地层以及解决关于其地质历史的问题其中一个问题是有关地中海地区无脊椎动物没有脊椎的动物于600万年前发生剧变的证据大部分更古老些的生物都几乎灭绝了，尽管有少数顽强的种类幸存了下来很少的一些动物成功地迁移到了大西洋不久后，这些动物又回来了，并带回了新的物种为什么这次距今较近的动物灭绝和迁移会发生呢？■Another taskfor theGlomar Challengersscientists wasto tryto determinetheorigin of the dome-like massesburied deepbeneath theMediterranean seafloor.aThesestructures hadbeen detectedyears earlierby echo-sounding instruments,but theyhadnever beenpenetrated in the courseof drilling.nWere theysalt domessuch asare commonalongthe UnitedStates GulfCoast,and ifso,why shouldthere havebeen somuch solidcrystallinesalt beneaththe floorof theMediterranean■Glomar Challenger号上的科学家们的另一个任务是尝试去确定深埋在地中海海底穹顶状巨块的起源这些结构在早些年被回声探测器探测过，但是它们从未被钻探过它们是像美国墨西哥海湾海岸一带的含盐穹顶状巨块吗？如果是的话，为什么在地中海海底之下会有这么多固体的结晶盐呢？With questionsuch asthese clearlybefore them,the scientistsaboardtheGlomarChallenger processedto theMediterranean tosearch forthe answers.On August23,1970,they recovereda sample.The sampleconsisted ofpebbles ofgypsum andfragments ofvolcanicrock.Not asingle pebblewas foundthat mighthave indicatedthat thepebblescame fromthe nearbycontinent.In thedays following,samples ofsolid gypsumwererepeatedly broughton deckas drillingoperations penetratedthe seafloor.Furthermore,thegypsum wasfound topossess peculiaritiesof compositionand structurethat suggestedithad formedon desertflats.Sediment aboveand belowthe gypsumlayer containedtinymarine fossils,indicating open-ocean conditions.As theydrilled into the centralanddeepest partoftheMediterranean basin,the scientiststook solid,shiny,crystalline saltfromthe corebarrel.Interbedded withthe saltwere thinlayers ofwhat appearedto bewindblownsilt.带着这些清楚摆在他们面前的问题，科学家们登上Glomar Challenger号前往地中海寻找答案1970年8月23日，他们找到了一个样本这个样本由石膏块和火山岩碎块组成周围没有发现一块能说明这些小石头是来自附近大陆的石头接下来的日子里，随着海底岩层钻探实验的进行，固体石膏样本被不断地放在甲板上而且，这些膏状物的组成和结构特性表明它们形成于沙漠在石膏层上下的沉积物中包含了微小的海洋生物化石，说明了这是开放性的海洋环境当钻到地中海盆地中心的最深处时，科学家们从钻管中获得了坚实的、光亮的结晶盐跟结晶盐嵌在一起的薄层像是被风吹起的泥沙层The timehad cometo formulatea hypothesis.The investigatorstheorized thatabout20million yearsago,theMediterranean was abroad seawaylinked tothe Atlanticby twonarrowstraits.Crustal movementsclosed thestraits,and thelandlocked Mediterraneanbeganto evaporate.Increasing salinitycaused bythe evaporationresulted intheextermination ofscores ofinvertebrate species.Only afew organismsespecially tolerantofvery saltyconditions remained.As evaporationcontinued,the remainingbrine saltwaterbecame sodense that the calcium sulfate ofthe hard layer wasprecipitated.In thecentraldeeper partofthebasin,the lastofthebrine evaporatedto precipitatemore solublesodiumchloride salt.Later,under theweight ofoverlying sediments,this saltflowedplastically upwardto formsalt domes.Before thishappened,however,the Mediterraneanwasa vastdesert3,000meters deep.Then,about

5.5million yearsago camethe deluge.Asa resultof crustaladjustments andfaulting,the Straitof Gibraltar,where theMediterraneannow connectstotheAtlantic,opened,and wateicascaded spectacularlyback intotheMediterranean.Turbulent waterstore intothe hardenedsalt flats,broke themup,andground themintothepebbles observedinthefirst sampletaken bythe Challenger.As thebasinwas refilled,normal marineorganisms returned.Soon layerof oceanicooze begantoaccumulate abovethe oldhardlayer.时间阐明了一个假设调查者们构思了这样的理论大约2,000万年前，地中海是一条宽阔的航道，它通过两条狭窄的海峡与大西洋连接地壳运动封闭了海峡，被陆地包围的地中海也开始蒸发由蒸发引起的越来越高的盐度造成大量无脊椎动物种类的灭绝只有一些能抵抗高盐度条件的物种保留下来随着蒸发的继续进行，盐水浓度太高以致硬地层的硫酸钙发生沉淀在盆地的中间深处，剩余盐水的持续蒸发形成更多的可溶的氯化钠盐后来，在上层沉淀物的重压下，盐向上形成了含盐的圆顶然而在这之前，地中海是一个3000米深的大沙漠然后，550万年前发生了洪水作为地壳调整和断层作用的结果，现在连接地中海和大西洋的直布罗陀海峡打开了，水流像瀑布一样壮观地涌回地中海湍急的水流冲击并摧毁了坚硬的含盐层，把它们磨成了Challenger号获得的第一份样本中人们所观察到的鹅卵石随着盆地的填充，普通的海洋生物又回来了不久后海洋软泥层开始在原先的硬地层上堆积The saltand gypsum,the faunalchanges,and theunusual gravelprovided abundantevidencethattheMediterraneanwasonce adesert.盐、石膏、动物区系的变更，还有不寻常的沙砾层都为地中海曾经是片沙漠的理论提供了充分的证据gypsum:a mineralmade ofcalciumsulfateand water。