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
54
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.
What is the main thesis of the article?
选项
A、Volcanic eruptions are not always deadly.
B、Older volcanic eruptions are more destructive.
C、Carbon dioxide emissions often give rise to global warming.
D、It is not easy to calculate the killing power of a volcanic eruption.
答案
B
解析
文章第一段直接点明了文章的主要论点。“Volcanoes were more destructive in ancienthistory…”(古代火山喷发更具破坏力)。故选B。
转载请注明原文地址:https://kaotiyun.com/show/DvUd777K
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
SharksPerformaServiceforEarth’sWatersItishardtogetpeopletothinkofsharksasanythingbutadeadlyenemy.They
ARichResourcesoftheStateBConnectionswiththeOutsideWorldCTransportationProblemDTheNativesoftheLandEColdCli
Itislogicalthatadetailedlearningofplantsandtheirpropertiesmustbeextremelyancient.Ourdirectcontactwithplants
Theuseofthechemicalmaypresentacertainhazardtothelaboratoryworkers.
TheyalwaysmockmebecauseIamugly.
Herbehaviorisextremelychildish.
随机试题
以下叙述中正确的是()。
设市场上每年对某厂生产的18寸彩色电视机的需求量是随机变量X(单位:万台),它均匀分布于[10,20],每出售一万台电视机,厂方获得利润50万元,但如果因销售不出而积压在仓库里,则每一万台需支付保养及其他各种损失费用10万元,问:18寸彩色电视机的年产量应
女性,68岁。原有肺心病病史。受凉后发热伴咳脓痰,发绀加重,次日神志模糊,嗜睡,血压12.0/9.0kPa,无病理反射。血气分析检查结果为:pH7.56,PaO27.33kPa(55mmHg),PaCO29.33kPa(70mmHg),HCO3-48m
患者,女性,23岁。1周前受凉感冒,未予特殊治疗。近日出现胸闷、心悸,心电图示窦性心律,频发室早,心率106次/分,体温36.5℃,血压100/60mini{g,听诊:第一心音低钝,未闻及明显杂音,怀疑病毒性心肌炎收入院。目前该病员应该
主动脉听诊区闻及收缩期喷射样杂音,向颈部传导,最可能的诊断是
下列不属于蒙药传统剂型的是()。
甲将自家的房产同时向乙、丙和丁作了抵押,其中,乙的抵押没有登记。后来由于不能按时偿还债务,房产被拍卖,共收入15万元,则以下表述正确的是()。
下列关于甲公司债务重组时的会计处理中,正确的是( )。20×6年末甲公司对固定资产进行改造时应转入在建工程的金额为( )万元。
Goodevening,ladiesandgentlemen!Firstofall,I’dliketo【B1】______asincerewelcometoyouall,thenewcomersofourc
A、Tobookatableforlunch.B、Tobookanairticket.C、Tomakeanappointment.D、Toasksomebodyforhelp.A
最新回复
(
0
)