Older Volcanic Eruptions(A级) 综合
Volcanoes were more destructive破坏in ancient history, not because they were bigger, but because the carbon碳dioxide二氧化物they released wiped擦去out life greater ease.转自环 球 网校edu24ol.com转自环 球 网校edu24ol.com
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 . Hecalculated the “killing efficiency效果” for these volcanoes by comparing比较the proportion比例of life they killed off with the volume of lava熔岩that they produced.他经过比较火山释放出的熔岩的体积与杀死生命的比例计算这些火山的杀伤效力。He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.转自环 球 网校edu24ol.com转自环 球 网校edu24ol.com
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消失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 CO.
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.
1. Why did older volcanic eruptions do more damage损伤 than more recent ones?
A. Because they killed off life more easily.
B. Because they were brighter.转自环 球 网校edu24ol.com转自环 球 网校edu24ol.com
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恐龙become extinct灭绝?
A) 300 million years ago.
B) 250 million years ago.转自环 球 网校edu24ol.com转自环 球 网校edu24ol.com
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小行星.
B) They died of drastic猛烈的climate change.
C) They were wiped off by a volcanic eruption.