英语六级巅峰阅读附详解-第30期-自然科学.docx

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英语六级巅峰阅读附详解第30期:自然科学

Icebergsareamongnature'smostspectacularcreations,andyetmostpeoplehaveneverseenone.Avagueairofmysteryenvelopsthem.Theycomeintobeing-somewhere-infaraway,frigidwaters,andthunderousnoiseandsplashingturbulence,whichinmostcasesnoonehearsorsees.Theyexistonlyashorttimeandthenslowlywasteawayjustasunnoticed.Objectsofsheerestbeauty,theyhavebeencalled.Appearinginanendlessvarietyofshapes,theymaybedazzlinglywhite,ortheymaybeglassyblue,green,orpurple,tintedfaintlyofdarkerhues（颜色）.Theyaregraceful,stately（宏伟的）,inspiringincalm,sunlitseas.Buttheyarealsocalledfrighteninganddangerous,andthattheyare-inthenight,inthefog,andinstorms.Eveninclearweatheroneiswisetostayasafedistanceawayfromthem.Mostoftheirbulkishiddenbelowthewater,sotheirunderwaterpartsmayextendoutfarbeyondthevisibletop.Also,theymayrolloverunexpectedly,churning（剧烈搅动）thewatersaroundthem.Icebergsarepartsofglaciersthatbreakoff,driftintothewater.floataboutawhileandfinallymelt.Icebergsafloattodayaremadeofsnowflakesthathavefallenoverlongagesoftime.Theyembodysnowsthatdrifteddownhundred,ormanythousand,orinsomecases,maybeamillionyearsago.Thesnowsfellinpolar-regionsandoncoldmountains,wheretheymeltedonlyalittleornotatallandsocollectedtogreatdepthsovertheyearsandcenturies.Aseachyear'ssnowaccumulationlayonthesurface,evaporationandmeltingcausedthesnowflakesslowlytolosetheirfeatherypointsandbecometinygrainsofice.Whennewsnowfellontopoftheold,ittooturnedintoicygrains.Soblanketsofsnowandicegrainsmountedlayeruponlayerandwereofsuchgreatthicknessthattheweightoftheupperlayerscompressedthelowerones.Withtimeandpressurefromabove,themanysmallicegrainsjoinedandchangedtolargercrystals,andeventuallythedeepercrystalsmergedintoasolidmassofice.冰山是大自然最壮观的杰作之一，而大多数人却从未见过。它们被一层神秘的面纱所笼罩。[1]冰山产生于某些遥远的冰冷水域中，生成时发出雷鸣般的响声，溅起巨浪，而在多数情况下没人听到或见过。它们昙花一现并渐渐消失无踪。它们被誉为最美丽的物体。[2]其形状变化多端，呈现出耀眼的白色或透亮的蓝色、绿色或紫色，带着丝丝淡淡的深色。在风平浪静、洒满阳光的海面上，它们是那么优雅、宏伟、激动人心。[3]然而在夜晚、在雾里以及在风雨中，它们也被认为是可怕和危险的，即使是在天气晴朗的日子，与其保持安全的距离