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
2024-04-26
33
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] What does "the puzzle"(Line 1, Para. 4)refer to?
选项
A、The cause of the ice-age cycle.
B、The duration of an ice-age cycle.
C、Whether the ice-age cycle is related to the changes in Earth’s orbit.
D、How fast the seas rose when the ice-age cycle was about to start.
答案
A
解析
第4段提到的“puzzle”是针对第3段讨论的话题的,第3段讨论的主题是“冰河时代周期循环的原因”,而该段最后一句提到至今为止,没有人能找到其确切的原因,所以在第4段称之为“puzzle”,由此可见,puzzle指的是“冰河时代周期循环的原因”,因此,本题应选A。
转载请注明原文地址:https://tihaiku.com/zcyy/3571914.html
相关试题推荐
Westerntattooists(纹身师)workwithaspecialelectricalinstrument,something
Westerntattooists(纹身师)workwithaspecialelectricalinstrument,something
Somethingveryunusualhappenedabout80,000yearsago,asEarth’slastice
Somethingveryunusualhappenedabout80,000yearsago,asEarth’slastice
Somethingveryunusualhappenedabout80,000yearsago,asEarth’slastice
Somethingveryunusualhappenedabout80,000yearsago,asEarth’slastice
AremarkablethinghappenedinNewYorkrecently:thestatelegislature,in
[originaltext]M:Maybeit’ssomethingIhavetomentionaboutIranians,wedon’
[originaltext]M:Maybeit’ssomethingIhavetomentionaboutIranians,wedon’
[originaltext]M:LookatthelowpricesonthesefashionableTVsets.Something
随机试题
Accordingtothepassage,todaymanygrandchildrenofimmigrants______.[br]M
InthispartoftheReadingsection,youwillread2passages.Youwillhave
WhichofthefollowingdoesnotbelongtothethreelevelsofSyntaxputforward
下列关于运用动画模拟微观变化进行化学教学的论述,不正确的是()。A.可以真实反
《劳动争议调解仲裁法》规定,集体劳动争议的劳动者一方在()以上。 A.3
双轨运行要定期检查双方的核算结果,比较手工证账表与计算机的输出是否一致,如果出现
银行承兑汇票的承兑银行,应当按照票面金额向出票人收取()的手续费。A:千分之一
在建筑防火设计中,按现行同家标准,建筑内下列哪些场所应设置疏散照明?()A.建
悬浇法施工时,预应力混凝土梁体一般分为()大部分浇筑。A.两 B.三
在一定条件下用强氧化剂如高锰酸钾、重铬酸钾等氧化水中有机物和无机物所消耗的氧量为
最新回复
(
0
)