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
41
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://jikaoti.com/ti/41qFFFFM
0
大学英语六级
相关试题推荐
A、Encouragethegrowthofreading.B、Changepeople’sattitudestoreading.C、Showhowreadingmethodshavebeenimproved.D、Expl
A、TeacherslikeProf.Johnsonarerare.B、Prof.Johnsonhaswonamilliondollars.C、TherearemanyteachersasgoodasProf.Jo
WiththestartofBBCWorldServiceTelevision,millionsofviewersinAsiaandAmericacannowwatchtheCorporation’snews【B1】
Anadvanceddegreeinbusinessstudiesisnowamustforanyambitiousandfocusedexecutivehopingtoclimbthecareerladderi
A、Itisstatic.B、Itisinmotion.C、Itcan’tbemeasured.D、It’sgettingbigger.A短文提到,直到17世纪前,天文学家仍认为宇宙大小是恒定不变的。A中的static“静止的”
A、Shehastochangethetimeforthetrip.B、Shehasn’tdecidedwheretogonextmonth.C、Shecan’taffordthetimeforthetrip
Nooneworddemonstratedtheshiftincorporations’attentioninthemid-1990sfromprocessestopeoplemorevividlythanthesi
给婴儿特别的礼物或给亲戚礼物,中国是有自己的文化的。如果是新生儿,玉或银手链或项链通常是很好的礼物,特别是那些只要宝宝一动就可以发出叮叮声的东西。另外,一些孩子的衣服,鞋子和手套也是很好的礼物。如果是大点的孩子,一些玩具或文具就好了。如果是老人,就要考虑一
A、Hecanofferamuchcheaperpriceforthiscar.B、Hisannualsavingsarequiteenoughtobuythiscar.C、Thiscarneedslessp
Aristotledefinedafriendas"asinglesouldwellingintwobodies".Howmanyfriendswehave,andhoweasilywemake,maintain
随机试题
消防滤水器安装在进水管底部,用以阻止水藻、石子、杂草等物吸入()。
小隐静脉()
75岁女患者,右大腿卵圆窝部反复出现圆形突起已多年,此次因便秘突出包块增大,用力还纳后右下腹持续疼痛伴呕吐而求医。下腹压痛,反跳痛肌紧张,叩诊肝浊音界缩小,肠鸣音减弱。
《本草纲目拾遗》新增的药物种数是()。
胃大部切除术后出现贫血的原因是()
【2006年第88题】如图6-5所示,采用同类钢材制作的具有相同截面面积、相同截面高度(h)和腹板厚度,翼缘宽度不等的三种钢梁,当钢梁与上翼缘混凝土楼板整浇时,钢梁跨中截面的抗弯承载力大小顺序为下列哪项?(提示:混凝土强度、钢梁与楼板的连接、钢梁的稳定均有
证券市场的基本经济功能是()
某公司在生产主要产品的同时,还生产了某种副产品。该种副产品可直接对外出售,公司规定的售价为每千克100元。某月主要产品和副产品发生的生产成本总额为500000元,副产品的产量为500千克。假定该公司按预先规定的副产品的售价确定副产品的成本,则主产品应负担的
阅读材料,回答问题。材料一明清时期,形成了一个积累大量财富的商人群体——淮扬盐商。康乾年间,“奢靡风习创于盐商,而操他业以致富者群慕效之”,扬州地区物质繁荣,名流荟萃,周边乃至全国都追慕扬州,以至“作事轩昂,向日‘扬气’……尽事奢华也”。——摘编自
已知:x=-6y=39则表达式"y\x*Sgn(x)"的值为( )。
最新回复
(
0
)