2. 外语
  3. Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger, but because the c

Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger, but because the c

admin2014-09-13  48
问题                          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(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 wanning 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(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 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.
Which of the following is NOT true according to Paragraph 3?
选项 A、Only 80 percent of marine genera survived the global warming caused by the Permian extinction.
B、It took 5 million years for the planet to recover from the Permian extinction.
C、The huge amount of volcanic activity and global warming 60 million years ago did not lead to mass extinction.
D、The cause of dinosaurs’ extinction has remained a controversial issue.
答案A
解析 根据第三段的前三句，二叠纪后的全球变暖毁灭了80％的海洋生物，因此只有20％的海洋生物度过了这场劫难。A项不正确，其他选项说法正确。
转载请注明原文地址:https://kaotiyun.com/show/aXQd777K
本试题收录于： 职称英语理工类C级题库职称英语分类
0

职称英语理工类C级

职称英语

相关试题推荐
随机试题
最新回复(0)