第四部分 閱讀理解（共六篇）
第五十篇
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.
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.
詞匯：
dioxide n. 二氧化物
lava n. 熔巖
Permian adj. 二疊紀(jì)
gigaton n. 十億噸梯恩梯
genera n. 種類
dinosaurs n. 恐龍
asteroid n. 小行星
注釋：
The Permian extinction 二疊紀(jì)物種滅絕
練習(xí)：
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.
2. How did Wignall calculate the killing power of those older volcanic eruptions?
A) By estimating how long they lasted.
B) By counting the dinosaurs they killed.
C) By studying the chemical composition of lava.
D) By comparing the proportion of life wiped out with the volume of lava produced.
3. When did dinosaurs become extinct?
A) 300 million years ago.
B) 250 million years ago.
C) 60 million years ago.
D) 65 million years ago.
4. What can be inferred from paragraph 3 concerning dinosaurs?
A) They were killed off by an asteroid.
B) They died of drastic climate change.
C) They were wiped off by a volcanic eruption.
D) The cause of their extinction has remained a controversial issue.
5. What is the main thesis of the article?
A) Volcanic eruptions are not always deadly.
B) Older volcanic eruptions were more destructive.
C) Carbon dioxide emissions often give rise to global warming.
D) It is not easy to calculate the killing power of a volcanic eruption.
答案與題解：
1．A 問題問的是：為什么遠(yuǎn)古的火山爆發(fā)比近期的火山爆發(fā)破壞性更大？第一段是這么說的：古代的火山更具破壞力，不是因為它們更大，而是因為它們釋放出的二氧化碳更能容易地毀滅生命。
2．D 問題問的是：Wignall是如何計算出遠(yuǎn)古火上爆發(fā)的殺傷力的？答案在第二段。第二段有這樣一句話：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．他通過比較火山釋放出的熔巖的體積與殺死生命的比例計算這些火山的殺傷效力。
3．C 問題問的是：恐龍是什么時候滅絕的?答案在第三段。其中有這么一句話：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．他沒有提及6千5百萬年前恐龍的滅絕是因為許多科學(xué)家相信恐龍的滅絕是受一顆小行星的影響。
4．D 問題問的是：第三段還可以推導(dǎo)出有關(guān)恐龍的什么樣的信息?在討論第三題的答案時，我們已經(jīng)注意到了，Wignall沒有提6千5百萬年前恐龍的滅絕是否跟火山爆發(fā)有關(guān)是因為許多科學(xué)家相信恐龍的滅絕是受一顆小行星的影響。這就說明，關(guān)于恐龍滅絕的原因在科學(xué)家之間是有分歧的。
5．B 問題問的是：文章的主要論點是什么？答案在文章的第一句：Volcanoes were more destructive in ancient history, ．．．（古代火山更具破壞力）。
