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
Blasts from the Past 1.Volcanoes were destructive in ancient history. Not because they were bigger, but because the carbon di
Blasts from the Past 1.Volcanoes were destructive in ancient history. Not because they were bigger, but because the carbon di
admin
2010-01-13
105
问题
Blasts from the Past
1.Volcanoes were destructive in ancient history. Not because they were bigger, but because the carbon dioxide they released wiped out life with greater ease.
2.Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions. Not all volcanic eruptions killed off large number of animals, but all the mass extinction cover 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.
3.Wignall calculated the "killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava 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.
4.The Permian 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 per cent of all marine genera at the time, and it took 5 million years for the planet to recover.
5.Yet 60 million years ago in the late Palaeocene 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 thousands of years. "The most recent ones hardly have an effect at all," Wignall says. He ignored the extinction which wiped out the dinosaurs at the end of the Cretaceous, 265 million years ago, because many scientists believe it was primarily caused by the impact of an asteroid.
6.Wignall thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2. Ocean chemistry may also have played a role. As the supercontinents broke up and exposed more coastline there may have been more weathering of silica rocks. This would have encouraged the growth of phytoplankton in the oceans, increasing the amount of CO2absorbed from the atmosphere.
7.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.
8.Courtillot 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 or sulphur dioxide emissions.
*
选项
答案
B
解析
the killing efficiency for older eruptions:较早的火山爆发在灭绝生物方面的效率。填入后生成的句子意思是:二叠纪生物灭绝这一事实用来说明较早的火山爆发在灭绝生物方面的效率。这一点我们在对第三题做题解时已经提到。
转载请注明原文地址:https://kaotiyun.com/show/pRGd777K
本试题收录于:
职称英语综合类基础题库职称英语分类
0
职称英语综合类基础
职称英语
相关试题推荐
Ordinaryplantsareunabletosurviveinthedesertmainlybecauseofthechangeableweather.Grassesandflowersindesertare
Peopleknewlongagohowanearthquakestarts.Ifyouareinthestreetwhenanearthquakeoccurs,stayinalargeopenspace.
It’sintheCardsInrecentyears,moreandmorepeoplehavebeenpayingforthingswithcreditcards.Therearenow565millio
SingingAlarmsCouldSavetheBlindIfyoucannotsee,youmaynotbeabletofindyourwayoutofaburningbuilding-andthat
TreesTreesareusefultomaninthreeveryimportantways:theyprovidehimwithwoodandotherproducts;theygivehimshade;
Onthetablewasavasefilledwithartificialflowers
WhyBuyShade-GrownCoffee?Whenpeopleargueaboutwhethercoffeeisgoodforhealth,they’reusuallythinkingofthehealt
TheAnimalsinDesertSomedesertanimalscansurvivetheverystrongsummerheatanddrynessbecausetheyhaveveryunusual
TheValueofMotherhoodInshoppingmalls,theassistantstrytopushyouintobuying"agifttothankherforherunselfish
TheValueofMotherhoodInshoppingmalls,theassistantstrytopushyouintobuying"agifttothankherforherunselfish
随机试题
简述政府间财政支出划分的原则。
积粉苔属于
下列关于脾切除术治疗特发性血小板减少性紫癜的说法正确的是( )。
中寒证的症状是
弛张热是指()
简述宪法解释与法律解释、宪法修改之间的关系。
某建筑基坑安全等级为二级,采用单层锚杆和单层支撑的支挡式结构,其嵌固稳定安全系数不应小于下列何项?
处于习俗道德水平阶段的学生道德判断的标准依赖于老师、家长等权威。()
Readthenewspaperarticlebelowaboutapartnershipbetweenindustryandschools.Aresentences16-22belowthearticle"Right"
______introducedthe"heroiccouplet"fromFranceintoEnglishpoetry.
最新回复
(
0
)