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
54
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
Tocoolitself,arhinocerossoaksinmudorwaterbecauseitsthickhidehasnosweatglands.
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
AncientWaterFromAfarItstreakedacrosstheskyonawarmMarcheveninglastyear,thencrashedintoastreetinthesma
Themailwasdelayedfortwodaysbecauseofthesnow-storm.
CarefulobservationsandsystematicstudiesofsunspotsSunspotsarecoolerthantherestofthesun’ssurfacebecause
TheHyper-XbroketherecordbecauseWhatdoesWernerJ,A.DahmsayabouttheHyper-Xtestflight?
TheHyper-XbroketherecordbecauseWhichofthefollowingisNOTtrueofthescramjetengine?
随机试题
某区人民检察院根据举报,立案侦查马某贪污一案。2003年4月6日,人民检察院对马某决定拘留,并于4月14日决定对马某进行逮捕。(中国政法2004年研)问题:贪污案件应由哪个机关立案侦查?
试论职权的形式。
男性,35岁,半年多来持续黄疸伴皮肤瘙痒,查体见巩膜、皮肤明显黄染,肝肋下3cm,质较硬,光滑,脾肋下6cm,化验血清抗线粒体抗体阳性,血总胆红素134μmol/L,结合胆红素88μmol/L,ALT30IU/L,GGT200U/L,最可能的诊断是
患者,女,70岁。胸骨后疼痛3小时不能缓解。心电图检查正常,临床医生疑为急性心肌梗死。可确诊的标志物是
患者喉痒咳嗽,痰中带血,口干鼻燥,舌质红,脉数,此病的病机是( )。
某人血红蛋白40g/L,白细胞计数2.5×109/L,血小板计数20×109/L。最可能是
对建筑施工企业在施工时偷工减料行为的处罚中,下列何种处罚行为不当?[2005年第85题]
标准的保单条款不包括( )。
Nomatterhowlowyouconsideryourself,thereisalwayssomeone______youwishingtheywerethathigh.
小方正在为本部门报考会计职称的考生准备相关通知及准考证,利用考生文件夹下提供的相关素材,按下列要求帮助他完成文档的编排。新建一个空白Word文档,利用文档“准考证素材及示例.docx”中的文本素材并参考其中的示例图制作准考证主文档,以“准考证.docx
最新回复
(
0
)