Disappearing Dinosaurs
消失的恐龙 I-12 / 012

For more than 160 million years, dinosaurs ruled Earth. Some were no larger than chickens. Others were more than 100 feet long and may have weighed 100 tons. Some dinosaurs ate plants. Others ate other dinosaurs! The last of these reptiles vanished about 65 million years ago.

Until recently, scientists have thought that dinosaurs disappeared slowly. They thought that the temperature on Earth cooled. Plants and dinosaurs that were used to warm weather couldn't survive the cold climate. Also, early mammals might have eaten dinosaur eggs. Over many years, all the dinosaurs finally died.

In 1980, two scientists came up with a new idea about how the dinosaurs vanished. Luis Alvarez and his son Walter studied a layer of clay. In this clay the two men found iridium. This substance is rarely found in Earth's crust. It is found in meteors that fall to Earth from outer space. The two men now think that dinosaurs might have died quickly.

The Alvarezes think that millions of years ago a huge meteorite might have slammed into warm, sunny Earth. The impact set a huge cloud of dust into the air. For months the dust cloud shut out the light of the Sun. With no sunlight all plants on Earth died. The plant-eating dinosaurs had no food, so they died too. The meat-eating dinosaurs then died quickly, because their food source was gone.

Today not all scientists agree with the idea of“quick death.” Some think the idea should be studied. As time goes by, scientists will continue to study how the dinosaurs disappeared.

Words and Phrases

dinosaur [ˈdaɪnəsɔ:(r)] 名 恐龙

reptile [ˈreptaɪl] 名 爬行动物

vanish [ˈvænɪʃ] 动 消失，突然不见

survive [səˈvaɪv] 动 幸存；活下来

mammal [ˈmæml] 名 哺乳动物

clay [kleɪ] 名 黏土，泥土

iridium [ɪˈrɪdɪəm] 名 铱

crust [krʌst] 名 外壳；地壳

meteor [ˈmi:tɪə(r)] 名 流星，陨星

outer space 太空；外层空间

meteorite [ˈmi:tɪəraɪt] 名 陨石

slam [slæm] 动 猛烈撞击

impact [ˈɪmpækt] 名 冲击力；碰撞

shut out 排除；把……关在外边

disappear [ˌdɪsəˈpɪə(r)] 动 不见，消失；不复存在

Practice

1. When did dinosaurs vanish from Earth?

A. about 65 million years ago

B. more than 100 million years ago

C. before a meteorite landed

2. What happened as Earth grew colder?

A. The mammals disappeared.

B. The dinosaurs died.

C. Meteorites fell.

3. When did the huge dust cloud fill the air?

A. after the plants died

B. when the meteorite fell

C. after the dinosaurs died

4. According to the Alvarezes, when did the dinosaurs die?

A. when Earth was sunny

B. thousands of years ago

C. after sunlight was shut out

译文

消失的恐龙

恐龙曾经主宰地球超过一亿六千万年之久。有的恐龙还不如鸡大，有的却超过100英尺（30.48米）长，而且体重可能达到了100吨。有些恐龙吃植物，有些则靠吃其他恐龙为生！然而这些爬行动物早在六千五百万年前就消声匿迹了。

直到最近，科学家们一直持有恐龙是慢慢灭绝的想法。他们认为地球的温度降低，导致习惯温暖气候的植物和恐龙无法在寒冷的气候中生存。另外，早期的哺乳动物可能以恐龙蛋为食。长此以往，恐龙最终绝迹。

1980年，两名科学家提出了关于恐龙灭亡的新观点。路易斯·阿尔瓦雷兹和他的儿子沃尔特研究了黏土层，他们在黏土中发现了金属铱。这种物质在地壳中很稀有，在由外太空坠落到地球的陨星上才找得到。于是两人现在认为恐龙的灭绝可能非常快。

阿尔瓦雷兹父子认为，数百万年前或许曾有颗巨大的陨石撞击了温暖晴朗的地球，撞击时产生了大量的尘雾，这些尘雾阻隔阳光长达数月。没有了阳光，地球上所有的植物都死亡了。以植物为食的恐龙因食物短缺而灭亡，而食肉恐龙也因食物来源的消失而快速灭亡。

时至今日，并不是所有的科学家都认同“快速死亡”一说。有些科学家认为这个想法还有待研究。随着时间的推移，科学家们将继续研究恐龙是如何灭绝的。

练习

1．恐龙是什么时候从地球上消失的？

A．大约在六千五百万年前

B．超过一亿年之前

C．在陨石撞地球之前

2．当地球气温变冷时发生了什么事？

A．哺乳动物消失了。

B．恐龙死亡了。

C．陨石降落了。

3．大量的尘雾何时布满在空中？

A．当植物死亡后

B．当陨石坠落时

C．在恐龙死亡后

4．依据阿尔瓦雷兹父子的研究，恐龙是何时灭亡的？

A．当地球气候晴朗的时候

B．几千年以前

C．当阳光被阻隔后