综合类AB级：模拟试题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 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 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. 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 thousands 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. He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2.www.zcyyw.com
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.
词汇：
dioxide n. 二氧化物
lava n. 熔岩
Permian adj. 二叠纪
gigaton n. 十亿吨梯恩梯
genera n. 种类
dinosaurs n. 恐龙
asteroid n. 小行星
注释：
The Permian extinction 二叠纪物种灭绝
练习：
1. Why did older volcanic eruptions do more damage than more recent ones?
A:Because they killed off life more easily.
B:Because they were brighter.
C:Because they were larger.
D:Because they were hotter.
本题正确答案为:A
本题解析:A 问题问的是：为什么远古的火山爆发比近期的火山爆发破坏性更大?第一段是这么说的：古代的火山更具破坏力，不是因为它们更大，而是因为它们释放出的二氧化碳更能容易地毁灭生命。