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
69
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
E
解析
Volcanic eruptions that caused no mass extinction:没有造成大量生物灭绝的火山爆发。上面讲到了“较早的火山爆发在灭绝生物方面的效率至少是较后来的对手的10倍”。第五段就是对“较后来的对手”的灭绝生物能力不行的证明。
转载请注明原文地址:https://kaotiyun.com/show/ORGd777K
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
PlantsinDesertOnlyspecialplantscansurvivetheterribleclimateofadesert,fortheseareregionswhentheannualrange
TheJoyofLivingAloneMoreandmoreAmericansarelivingalone.Somelivealonebecauseofdivorceorthedeathofapartner.
NewFoodsandtheNewWorldInthelast500years,nothingaboutpeople—nottheirclothes,ideas,orlanguages—haschanged
TreesTreesareusefultomaninthreeveryimportantways:theyprovidehimwithwoodandotherproducts;theygivehimshade;
TreesTreesareusefultomaninthreeveryimportantways:theyprovidehimwithwoodandotherproducts;theygivehimshade;
TreesTreesareusefultomaninthreeveryimportantways:theyprovidehimwithwoodandotherproducts;theygivehimshade;
WhateverHappenstoOldComputers?Youhavejustgotanewcomputerandyouaredelightedwithit.Itisdoingeverythingyo
ForestsforCitiesYouarestandinginabeautifulforestinJapan.Theairiscleanandsmellslikeplantsandflowers.Ther
WhyBuyShade-GrownCoffee?Whenpeopleargueaboutwhethercoffeeisgoodforhealth,they’reusuallythinkingofthehealt
TheValueofMotherhoodInshoppingmalls,theassistantstrytopushyouintobuying"agifttothankherforherunselfish
随机试题
Whatarethereinoursocietynowadays?Thereare_________________.
试述近现代时期中外国家政权机构的秘书工作的不同之处。
A.一级医疗事故B.二级医疗事故C.三级医疗事故D.四级医疗事故E.医疗过失造成患者明显人身损害的其他后果的属于
急性感染(如金黄色葡萄球菌感染)时白细胞出现的情况是再生障碍性贫血时,白细胞出现的情况是
在某砂砾石层中进行标准贯入试验,锤击数已达50击,实际贯入深度仅为13cm。按有关公式进行换算,相当于贯入30cm的锤击数N可取下列()项数值。
根据有效市场假说,下列说法中正确的有()。2014(卷Ⅰ)、(卷Ⅱ)
2015年第一季度,A省商品房销售面积1175.2万平方米,下降13.4%,降幅比1—2月收窄13.8个百分点。其中,商品住宅销售面积1036.3万平方米,下降15%;办公楼销售面积15.2万平方米,下降48.7%;商业营业用房销售面积111.1万平方米,
Mostworthwhilecareersrequiresomekindofspecializedtraining.Ideally,therefore,thechoiceofan【C1】______shouldbemade
makesomefoodtoeattrytofindsomething
_____isnoreasonfordischargingher.
最新回复
(
0
)