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
Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger, but because the c
Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger, but because the c
admin
2014-09-13
31
问题
Older Volcanic Eruptions
Volcanoes were more destructive in ancient history, not because they were bigger, but because the carbon dioxide they released wiped out life with greater ease.
Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions. Not all volcanic eruptions killed off large numbers of animals, but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock. To his surprise, the older the massive volcanic eruptions were, the more damage they seemed to do. He calculated the "killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava(熔岩)that they produced. He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.
The Permian(二叠纪)extinction, for example, which happened 250 million years ago, is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe. Those volcanoes are thought to have pumped out about 10 gigatonnes of carbon as carbon dioxide. The global warming that followed wiped out 80 percent of all marine genera(种类)at the time, and it took 5 million years for the planet to recover. Yet 60 million years ago, there was another huge amount of volcanic activity and global warming but no mass extinction. Some animals did disappear but things returned to normal within ten thousand of years. "The most recent ones hardly have an effect at all, " Wignall says. He ignored the extinction which wiped out the dinosaurs 65 million years ago, because many scientists believe it was primarily caused by the impact of an asteroid(小行星). He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO
2
.
Vincent Courtillot, director of the Paris Geophysical Institute in France, says that Wignall’ s idea is provocative. But he says it is incredibly hard to do these sorts of calculations. He points out that the killing power of volcanic eruptions depends on how long they lasted. And it is impossible to tell whether the huge blasts lasted for thousands or millions of years. He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced, and that lava volume may not necessarily correspond to carbon dioxide emissions.
When did dinosaurs become extinct?
选项
A、300 million years ago.
B、250 million years ago.
C、60 million years ago.
D、65 million years ago.
答案
D
解析
由文章第三段倒数第二句话“He ignored the extinction which wiped out the dinosaurs 65million years ago…”可知,恐龙是在6 500万年前灭绝的。故选D。
转载请注明原文地址:https://kaotiyun.com/show/RvUd777K
本试题收录于:
职称英语综合类A级题库职称英语分类
0
职称英语综合类A级
职称英语
相关试题推荐
SharksPerformaServiceforEarth’sWatersItishardtogetpeopletothinkofsharksasanythingbutadeadlyenemy.They
SharksPerformaServiceforEarth’sWatersItishardtogetpeopletothinkofsharksasanythingbutadeadlyenemy.They
Weareawareofthepotentialproblems.
OnHalloween,childrenintheUnitedStatesoftendressupasManychildrenintheUnitedStateslikeThanksgivingbecause
ARichResourcesoftheStateBConnectionswiththeOutsideWorldCTransportationProblemDTheNativesoftheLandEColdCli
Becauseofthepopularityoftheregion,itisadvisabletobookhotelsinadvance.
FinancialRisksSeveraltypesoffinancialriskareencounteredininternationalmarketing;themajorproblemsincludecommercia
"HappyBirthdaytoYou"ThemainproblemindiscussingAmericanpopularcultureisalsooneofitsmaincharacteristics:itwon’
ABuildingMaterialsBNeedofGreaterBuildingVarietiesinModemLifeCRestorationofAncientCivilizationsDEvolutioni
TheFatProblemthatMenFaceItisapleasuretoseemenofacertainageworryingabouttheirweight.Listeningtothemi
随机试题
在ABO血型系统中,H抗原表达最弱的血型是
护理职业道德的本质在于
如图所示,三棱柱A沿三棱柱B的光滑面滑动,三棱柱A重P,三棱柱B重Q,三棱柱B的斜面与水平成α角,初始系统静止,则三棱柱A沿斜面下滑时三棱柱B的加速度为()。
石灰工业废渣稳定土可分为()几类。
股份有限公司的设立,可以采取发起设立或者募集设立的方式。对于上述两种方式,下列表述中,正确的有()。
2008年12月31日,甲公司将一台生产用大型机器设备以110万元的价格销售给乙公司,账面原价为200万元。同时甲公司与乙租赁公司签订了一份融资租赁合同将该设备租回。合同主要条款及其他有关资料如下:(1)租赁标的物:大型机器设备。(2)租赁
人格
ThebesttitleforthistextcouldbeTheterm"oomph"(Paragraph3)inthetextdenotes
一台交换机具有16个100/1000Mbps全双工下联端口,它的上联端口带宽至少应为()。
2015年9月,某公司卖出12月到期的S&P500指数期货合约,期指为1400点,到了12月份股市大涨,公司买入100张12月份到期的S&P500指数期货合约进行平仓,期指点为1570点。S&P500指数的乘数为250美元,则此公司的净收益为(
最新回复
(
0
)