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 ca
Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger,but because the ca
admin
2016-08-16
42
问题
Older Volcanic Eruptions
Volcanoes were more destructive in ancient history, not because they were bigger,but because the carbon dioxide(二氧化碳)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 eruption skilled 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(十亿吨)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 tens of thousands of years. "The most recent ones hardly have an effect at all," Wignall says. He ignored the extinction which wiped out the dinosaurs(恐龙)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、Carbon dioxide emissions often give rise to global warming.
C、Older volcanic eruptions are more destructive.
D、It is not easy to calculate the killing power of a volcanic eruption.
答案
C
解析
文章开篇就讲火山在远古时代的破坏力更强,然后讲火山喷发导致生物的灭绝,以及现代科学家怎么计算火山的杀伤力,故本文的主旨就是说远古火山喷发的破坏性更大。故选C。
转载请注明原文地址:https://kaotiyun.com/show/KmGd777K
本试题收录于:
职称英语理工类A级题库职称英语分类
0
职称英语理工类A级
职称英语
相关试题推荐
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
Themegaphonemakesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutina
Themailwasdelayedfortwodaysbecauseofthesnow-storm.
Sinceancienttimespeoplehavefoundvariouswaystopreservemeat
TheHyper-XbroketherecordbecauseWhatdoesNASAplantodo?
TheHyper-XbroketherecordbecauseWhatdoesWernerJ,A.DahmsayabouttheHyper-Xtestflight?
TheHyper-XbroketherecordbecauseWhichofthefollowingisNOTtrueofthescramjetengine?
随机试题
应与腹股沟斜疝鉴别的疾病包括
同一包装商品内含有多件同种定量包装商品的,应当标注(),或者标注总净含量。
肠套叠最常见的类型是
发电机内部故障时,要对发电机进行灭磁,_________起到迅速切断励磁电流的作用。
当需要证实组织有能力稳定地提供满足顾客和适用的法律法规要求的产品时,组织不能采用_________。
某美国旅游团进入餐厅之后,要求将中餐换成西餐,导游人员的正确做法是()。
面对国内市场上冰箱生产厂家的激烈竞争,我国某冰箱生产企业在市场上率先进行降价,以此提高市场占有率,这种行为:
《二月提纲》
A、 B、 C、 D、 D
ElectricCars:Low-impactVehicleAfteryearsoffalsestarts,GeneralMotorshasatlastsetadateforputtingitsfirstb
最新回复
(
0
)