托福寫作范文之地球板塊構(gòu)造理論

/智課網(wǎng)TOEFL備考資料托福寫作范文之地球板塊構(gòu)造理論您當(dāng)前的位置?智課教育官網(wǎng)?托福?托福寫作?文章正文?

出國英語考試有哪些雅思6.5是什么水平雅思閱讀評分標(biāo)準(zhǔn)托福閱讀評分標(biāo)準(zhǔn)雅思和托福的區(qū)別?

PｌatｅTeｃtonｉcｓandＳea-ｆloorＳｐｒeadiｎg

Thetheoryｏfplａｔｅtectoniｃｓdeｓcribesthemotioｎsofthelithosphｅre，theｃｏmｐａratｉvelｙｒｉgｉdｏｕtｅｒlayｅrofｔhｅEarththatincｌudｅsａlltｈecｒuｓtanｄpａrtｏftｈeuｎdeｒlｙｉｎｇmantle.Thelｉthｏsphereisdivｉdｅｄｉntoafewdoｚenplatesｏｆvarioｕssiｚesａnｄshapes，ｉnｇｅｎerａltheplatesａｒeinmotｉonwiｔhreｓｐecｔtoｏneanothｅr.Amiｄ—ocｅaｎridgｅisabounｄａｒｙｂetweeｎplａt(yī)eswherenｅwlithｏｓpｈｅｒｉｃｍaｔｅrialisiｎjeｃｔｅｄfrombeｌｏw．Astｈeplaｔesdｉvergｅfrｏmaｍｉd－ｏcｅanridｇeｔheｙsliｄeonamｏreｙielｄinglａyeraｔtｈebａsｅofｔｈｅlｉｔhosｐhｅre。

ＳincethesizeoftheEarthｉｓessentiallyｃonstant，newliｔｈoｓpherecaｎbecrｅatｅdattｈｅｍid-oceaｎrｉdgｅsonｌyifanequａｌamountoflitｈｏspheriｃmatｅrｉａｌiscoｎsumedelseｗheｒe.Theｓiteｏｆthiｓdestructionisａnｏthｅrkｉnｄofplateboｕｎｄary:ａseｄuｃtｉonzone.Therｅoneplａt(yī)eｄivｅｓuｎｄeｒtheedgeｏfanothｅrandiｓreｉｎｃoｒpｏrａt(yī)ｅｄintothemantle．Bｏtｈkｉndsofplateｂｏundａrｙａreassociateｄwithfａuｌｔsyｓtemｓ,eａrtｈquakesaｎdvolcａnｉｓm，bｕtthｅkindsofgeologicaｃtivityobsｅrvedaｔthｅtwoboundａｒｉｅｓareqｕitｅｄifferenｔ.

?Theideaofｓea-fｌｏorspｒeadinｇactuallypｒｅcededthetheoryofｐlａt(yī)etectoniｃｓ．Initsｏｒiｇinaｌversiｏn，iｎtｈｅearｌｙ1９60’s，ｉtdｅsｃribedｔｈecｒｅａｔｉonanddestｒuｃｔｉonofｔhｅocｅａnflｏoｒ,buｔｉｔdｉdｎotsｐｅcｉfyriｇiｄliｔhｏsphericpｌates．Thehypoｔheｓiswaｓsubｓtanｔiａt(yī)eｄsoonafterwarｄｂyｔhediscｏverytｈaｔperｉodｉcrevｅrｓaｌｓoftheEarth'ｓｍａgneticfieｌｄａreｒｅｃｏｒdedinｔheoｃeaｎiｃcruｓt．Asmagｍariｓesundeｒtheｍid－ｏｃｅaｎｒidｇe，ferromagneｔicmｉnｅraｌsｉntｈeｍagmabｅcomeｍaｇnetizedintｈedｉｒectionofthemａgmaｂecomemagneｔizediｎｔhediｒｅctionofｔhegeｏmagnｅticfｉeｌd。Ｗhentｈeｍagmａcｏｏｌsanｄｓolidｉfiｅs，tｈｅｄｉrecｔｉｏnaｎdthepoｌarityofｔhefｉeldaｒepresｅｒvedintheｍagnｅtizedvolcanｉcrock。Reｖeｒｓalsoｆｔhｅfieldgivｅriseｔｏａseriesofmａgnetiｃstriｐｅｓruｎnｉｎgparalleltotheaｘｉsoftheriｆt.Theoceanｉｃcrustthusserｖesaｓaｍaｇnetictaperecoｒdiｎgoftｈehistｏryoｆthegeomagnetｉｃfieldthａｔｃanbedatｅdindependently；thｅｗｉdthofthestrｉpesiｎdiｃａt(yī)ｅstheｒaｔ