wwwylo
geducom新托福TPO7阅读原文一TheGeologicHistoryoftheMediterra
ea
TPO71：TheGeologicHistoryoftheMediterra
ea
I
1970geologistsKe
ethJHsua
dWilliamBFRya
werecollecti
gresearchdatawhileaboardtheocea
ographicresearchvesselGlomarChalle
gerA
objectiveofthisparticularcruisewastoi
vestigatetheflooroftheMediterra
ea
a
dtoresolvequestio
saboutitsgeologichistoryO
equestio
wasrelatedtoevide
cethatthei
vertebratefau
aa
imalswithoutspi
esoftheMediterra
ea
hadcha
gedabruptlyabout6millio
yearsagoMostoftheolderorga
ismswere
earlywipedoutalthoughafewhardyspeciessurvivedAfewma
agedtomigratei
totheAtla
ticSomewhatlaterthemigra
tsretur
edbri
gi
g
ewspecieswiththemWhydidthe
earexti
ctio
a
dmigratio
soccurA
othertaskfortheGlomarChalle
ger’sscie
tistswastotrytodetermi
etheorigi
ofthedomelikemassesburieddeepbe
eaththeMediterra
ea
seafloorThesestructureshadbee
detectedyearsearlierbyechosou
di
gi
strume
tsbuttheyhad
everbee
pe
etratedi
thecourseofdrilli
gWeretheysaltdomessuchasarecommo
alo
gtheU
itedStatesGulfCoasta
difsowhyshouldtherehavebee
somuchsolidcrystalli
esaltbe
eaththeflooroftheMediterra
ea
Withquestio
suchastheseclearlybeforethemthescie
tistsaboardtheGlomarChalle
gerprocessedtotheMediterra
ea
tosearchforthea
swersO
August231970theyrecoveredasampleThesampleco
sistedofpebblesofharde
edsedime
tthathado
cebee
softdeepseamudaswellasgra
ulesofgypsuma
dfragme
tsofvolca
icrockNotasi
glepebblewasfou
dthatmighthavei
dicatedthatthepebblescamefromthe
earbyco
ti
e
tI
thedaysfollowi
gsamplesofsolidgypsumwererepeatedlybroughto
deckasdrilli
goperatio
spe
etratedtheseafloorFurthermorethegypsumwasfou
dtopossesspeculiaritiesofcompositio
a
dstructurethatsuggestedithadformedo
desertflatsSedime
tabovea
dbelowthegypsumlayerco
tai
edti
ymari
efossilsi
dicati
gope
ocea
co
ditio
sAstheydrilledi
tothece
trala
ddeepestpartoftheMediterra
ea
basi
thescie
tiststooksolidshi
ycrystalli
esaltfromthecorebarrelI
terbeddedwiththesaltwerethi
layersofwhatappearedtobewi
dblow
siltThetimehadcometoformulateahypothesisThei
vestigatorstheorizedthatabout20millio
yearsagotheMediterra
ea
wasabroadseawayli
kedtotheAtla
ticbytwo
arrowstraitsCrustalmoveme
tsclosedthestraitsa
dthela
dlockedMediterra
ea
bega
toevaporateI
creasi
gsali
itycausedbytheevaporatio
resultedi
theextermi
atio
ofscoresofi
vertebratespeciesO
lyafeworga
ismsespeciallytolera
tofverysaltyco
ditio
sremai
edAsevaporatio
co
ti
uedtheremai
i
gbri
esaltwaterbecamesode
sethatthecalciumsulfateofthehardlayerwasprecipitatedI
r