首页
登录
职称英语
Something very unusual happened about 80,000 years ago, as Earth’s last ice
Something very unusual happened about 80,000 years ago, as Earth’s last ice
游客
2024-04-12
35
管理
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." [br] 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、70,000
D、11,000
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://tihaiku.com/zcyy/3551972.html
相关试题推荐
Thehealth-careeconomyisfilledwithunusualandevenuniqueeconomicrela
[originaltext](20)Agrowingnumberofwomenaredevelopingsomethingcalle
[originaltext]W:Well,youseemtohavesomethingonyourmind,Philip.M:Yes,
[originaltext](16)Whenwemakefriends,itcanhelptohavesomethinginc
[originaltext](16)Whenwemakefriends,itcanhelptohavesomethinginc
[originaltext](16)Whenwemakefriends,itcanhelptohavesomethinginc
Allourdreamshavesomethingtodowithourfeelings,fears,longings,wish
Allourdreamshavesomethingtodowithourfeelings,fears,longings,wish
Allourdreamshavesomethingtodowithourfeelings,fears,longings,wish
Allourdreamshavesomethingtodowithourfeelings,fears,longings,wish
随机试题
Driverlesstrainsareatypeoftrainfirstdevelopedinthe1960s.Asthename
TulipswereintroducedintoHollandbeforethe17thcenturybutitdidnott
下面在绘图中哪些对softlight(柔光)模式的描述是正确的:
某高速公路工程交工验收,检测人员需要对路面进行现场检测。该工程的路面为沥青混凝土
女性,25岁,心悸、甲状腺肿大,并伴有轻度呼吸不畅,压迫感,首次妊娠两个月余.诊
"亚硝酸钠一硫代硫酸钠"疗法:立即将亚硝酸异戊酯1~2支包在手帕或纱布内弄碎,给
不符合大肠癌扩散的描述是A.可直接蔓延至邻近器官 B.可经淋巴道转移到结肠上、
与一般的银行储蓄存款相比,大额可转让定期存单的特点有()。A.利率可以是固定的
(2014年真题)甲公司是一家化工生产企业,生产单一产品,按正常标准成本进行成本
根据《支付结算办法》的规定,采用汇兑方式,如果收款人转账支付的,该账户的款项可以
最新回复
(
0
)