首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Something very unusual happened about 80,000 years ago, as Earth’s last ice age was getting started. Sea levels that had been dr
Something very unusual happened about 80,000 years ago, as Earth’s last ice age was getting started. Sea levels that had been dr
admin
2014-05-30
48
问题
Something very unusual happened about 80,000 years ago, as Earth’s last ice age was getting started. Sea levels that had been dropping for thousands of years—as more and more water became trapped in expanding glaciers(冰川)—suddenly rose, according to a new study. Then after a few thousand years, the levels fell again. Although the researchers haven’t found the cause of this phenomenon, they say the findings could force at least a partial rethinking of the mechanisms governing Earth’s climate.
For the past several hundred thousand years, our planet seems to have followed a fairly regular climate cycle. About every 100,000 years, kilometers-thick ice sheets form atop the northernmost reaches of North America, Europe, and Asia and extend well into the mid-latitudes. The ice sheets also tie up so much seawater that ocean levels can drop by over 100 meters. Then, after about 90,000 years, the glaciers retreat and land reappears, until the next ice age begins. The last ice age ended about 11,000 years ago.
Various researchers going back nearly a century have attempted to isolate the cause of the ice-age cycle. They have uncovered several factors —periodic changes in Earth’s orbit around the sun, for example—that seem to be in play. But so far no one has presented the definitive answer.
In the recently published Science, a team doesn’t so much solve the puzzle as reinforce the uncertainties about how the ice-age cycle behaves. What they’ve found is very strong evidence that when Earth should have been preparing for the last ice age, the seas rose.
The researchers found that sea level 80,000 years ago had rebounded to the point where it rose 1 meter higher than it is today. And it could have risen quite quickly, as much as 2 meters per century, says geochemist Jeffrey Dorale of the University of Iowa.
That suggests the glaciers were melting at a tremendous rate. Even half that rate would still be "a major finding," Dorale says. So it "has major implications for future concerns with sea-level change."
The study "shows persuasive evidence" for a surge in sea level about 80,000 years ago, says geologist Daniel Muhs of the U.S. Geological Survey in Denver. He says the findings help make a "powerful" argument for the phenomenon. Still mysterious, however, are other data, taken from Barbados and New Guinea, that also suggest rising sea level about 80,000 years ago but not nearly as much of a change. It means, Muhs says, "that there is much about interpreting the geologic(地质学的)record of sea-level variation that we still do not understand."
It’s believed that, for the past several hundred thousand years, each ice age would last an average of _____years.
选项
A、100,000
B、90,000
C、70000
D、11000
答案
B
解析
第2段第2句提到每10万年,冰河时期就开始形成,第4句提到,约9万年后,冰川退去,陆地重现,由此可见,在过去的几十万年间,每个冰河时期大概持续9万年,因此本题应选B。
转载请注明原文地址:https://kaotiyun.com/show/qM17777K
0
大学英语六级
相关试题推荐
A、Thecompanydoesnothavetheman’sresume.B、Theman’sinterviewmightbesuccessful.C、Thecompanyhasdecidedtohirethem
Hasyourchildcrackedabookthissummer?Althoughadultsoftenjumpatthechancetocatchupontheirreadingduringvaca
Formanypeopletoday,readingisnolongerrelaxation.Tokeepuptheirworktheymustreadletters,reports,tradepublication
A、Focusonthepersonwhositsinthemiddle.B、Giveequaltimetomakeeyecontactwitheveryinterviewer.C、Focusonthequest
A、Hecan’tcatchupwithhisclassmates.B、HefindstheEnglishcourseloadtooheavy.C、Heisnotinterestedinhispresentmaj
Politicalplatformsareusuallywrittenforelectioncampaignpurposes,thenquicklyscrappedafterapresidentialelection.But
TheFutureIsAnotherCountryAcoupleofmonthsorsoafterbecomingBritain’sprimeminister,DavidCameronwantedafewt
A、ThemeritsanddrawbacksofalargepopulatioaB、Thedisadvantagesofalargepopulation.C、Theadvantagesofasmallpopulati
In2011,manyshopperschosetoavoidthefranticcrowdsanddotheirholidayshoppingfromthecomfortoftheircomputer.Sales
A、She’sunimpressedbywhatthemantoldher.B、Shedoubtsshecanaffordit.C、Shedoesn’tthinkit’ssuitableforher.D、She’s
随机试题
在科学管理理论中,提出了14条管理原则的人是()
《海牙规则》规定,如果货物的灭失和损坏不明显,收货人将索赔通知提交承运人的时间应是在收到货物之日起()
Misjudgingsomeone’suseofsilencecantakeplaceinmanycontextsandonmanylevels.Takepausingforexample.One’sconversa
两个主轴方向柱距均不小于()m、无桥式起重机且无柱间支撑的大柱网厂房,柱截面抗震验算应同时计算两个主轴方向的水平地震作用,并应计入位移引起的附加弯矩。
当防火间距不足时,可采取的措施有()。
直接标价法是用一定单位的本国货币来计算应收若干单位的外国货币。()
人心脏的左心室连接着()。
变色龙的体色随环境颜色而变化,这是生物与环境相适应的一种现象,下列现象与此不相类似的是()。
某国连续四年的统计表明,在夏令时改变的时间里比其他时间的车祸高4%。这些统计结果说明时间的改变严重影响了某国司机的注意力。得出这一结论的前提条件是()
TheThree-YearSolutionA)HartwickCollege,asmallliberal-artsschoolinupstateNewYork,makesthisoffertowellprepareds
最新回复
(
0
)