考研真题笔记模板题库资源推介平台
工作时间:9:00 ~ 21:00
Icebergs
Icebergsareamongnature‘smostspectacularcreations,andyetmostpeoplehaveneverseenone.Avagueairofmysteryenvelopsthem.Theycomeintobeing--somewhere--infaraway,frigidwaters,amidthunderousnoiseandsplashingturbulence,whichinmostcasenoonehearsorsees.Theyexistonlyashorttimeandthenslowlywasteawayjustasunnoticed.
Objectsofsheerestbeautytheyhavebeencalled.Appearinginanendlessvarietyofshapes,theymaybedazzlinglywhite,ortheymaybeglassyblue,greenorpurple,tintedfaintlyorindarkerhues.Theyaregraceful,stately,inspiring--incalm,sunlightseas.Buttheyarealsocalledfrighteninganddangerous,andthattheyare--inthenight,inthefog,andinstorms.Eveninclearweatheroneiswisetostayasafedistanceawayfromthem.Mostoftheirbulkishiddenbelowthewater,sotheirunderwaterpartsmayextendoutfarbeyondthevisibletop.
Also,theymayrolloverunexpectedly,churningthewatersaroundthem.Icebergsarepartsofglaciersthatbreakoff,driftintothewater,floataboutawhile,andfinallymelt.Icebergsafloattodayaremadeofsnowflakesthathavefallenoverlongagesoftime.Theyembodysnowsthatdrifteddownhundreds,ormanythousands,orinsomecasesmaybeamillionyearsago.Thesnowsfellinpolarregionsandoncoldmountains,wheretheymeltedonlyalittleornotatall,andsocollectedtogreatdepthsovertheyearsandcenturies.
Aseachyear‘ssnowaccumulationlayonthesurface,evaporationandmeltingcausedthesnowflakesslowlytolosetheirfeatherypointsandbecometinygrainsofice.Whennewsnowfellontopoftheold,ittooturnedtoicygrains.Soblanketsofsnowandicegrainsmountedlayeruponlayerandwereofsuchgreatthicknessthattheweightoftheupperlayerscompressedthelowerones.Withtimeandpressurefromabove,themanysmallicegrainsjoinedandchangedtolargercrystals,andeventuallythedeepercrystalsmergedintoasolidmassofice.
全文翻译:冰山
冰山是大自然最壮观的创造之一,但大多数人却从未看到过冰山 ,一种朦胧神秘的气氛笼罩着它们。冰山形成于久远的 、寒冷的水体中,而且伴随着雷声轰鸣般的嘈杂和水花汹涌的风暴,但却无人耳闻目睹 。冰山仅存在短短的一段时间就慢慢地悄无声息地融化掉。冰山具有最纯粹的美 ,人们如是说。
冰山呈现出千姿百态,可能白得耀眼,或者是闪耀着蓝色、绿色或紫色的玻璃般的光芒 ,或浓或淡 。它们在平静的阳光照耀的海水中显得优雅堂皇,令人浮想联翩。但是人们亦把冰山称为恐怖的和危险的。它们的确如此--在夜间,雾天和风暴肆虐时.即便是在晴朗的天气里,与它们保持一段安全距离也是明智的 。冰山的大部分体积稳藏于水下 ,因此其水下部分的伸展远远超过可见的顶部。冰山也可能出人意料地翻滚,剧烈地搅动周围的水体。冰山是冰川的一部分,从冰川断裂漂流进水中 ,一段时间后融化。今天的冰山由多年前降落的雪花形成 。
它们的体内是数百年,或数千年,有时甚至是数百万年前的降雪。这些雪花落在极地或寒冷的山上 ,仅有少量融化或根本不融化,这样经过许多年或许多世纪后积累了巨大的深度。由于每年的雪花积累在表面之上,蒸发和融化使得雪花慢慢失去其羽状尖端而变成微小的冰粒 。当新的雪花降落到旧的表面上 ,也变成了冰粒。因而雪花覆盖层和冰粒层层堆积起来直到如此之大的厚度以致较上层的重量压缩较下层。在时间和压力的作用下,许多小冰粒结合到一起变成更大的晶体,最终较底层的晶体合并成庞大而坚固的冰块 。