【英语时差8,16】海洋杀手

Don: Time now for another episode of A Moment of Science's "Did You Know..." So,Ya?l, did you know that there have been about twenty-three mass extinctions since life began on earth?

Ya?l: I know there've been a few extinctions, Don, but not that many!

D: Yep. Many were of prehistoric¹ bacteria and other single-celled microorganisms. But in the past 540 million years or so there have been about five mass extinctions, mainly of marine² plants and animals but also of land organisms.

Y: Well, I know that the dinosaurs³ disappeared about sixty-five million years ago,possibly due to a large meteor that crashed into earth and blotted⁴ out the sun. But what caused all those other extinctions?

D: That's been a mystery for a long time. But now some scientists think that most mass extinctions have been driven by the rise and fall of sea level. That may sound strange, but consider that millions of years ago a shallow sea covered the entire middle   section of North America. That sea grew and shrank back several times. Each time it drained it caused entire species of sea plants and creatures to die off. The last time it  drained was around sixty-five million years ago--when the dinosaurs disappeared.

Y: OK, I understand how a sea vanishing would kill off marine life. But did the sea's disappearance⁵ also have something to do with the dinosaurs going extinct?

D: Maybe. When a sea disappears it has a big effect on climate. All that water provides heat and moisture. And when a sea drains, the climate becomes drier and colder. So the change in climate may have combined with the meteor impact to kill off the dinosaurs.  

1 prehistoric   

adj.（有记载的）历史以前的，史前的，古老的

参考例句：

• They have found prehistoric remains.他们发现了史前遗迹。
• It was rather like an exhibition of prehistoric electronic equipment.这儿倒像是在展览古老的电子设备。

2 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

3 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

4 blotted   

涂污( blot的过去式和过去分词 )； （用吸墨纸）吸干

参考例句：

• She blotted water off the table with a towel. 她用毛巾擦干桌上的水。
• The blizzard blotted out the sky and the land. 暴风雪铺天盖地而来。

5 disappearance   

n.消失，消散，失踪

参考例句：

• He was hard put to it to explain her disappearance.他难以说明她为什么不见了。
• Her disappearance gave rise to the wildest rumours.她失踪一事引起了各种流言蜚语。