《英语流行话题阅读:语境识词4500》43 What Caused the K-T Mass Extinction?

　　Unit 43
What Caused the K-T Mass Extinction¹?
The latter part of the Cretaceous Period was a time of continental² drift and accompanying volcanic³ activity. The supercontinent was splitting up and the continents were taking on their modern-day forms. Many mountain ranges were formed. The sea levels rose during the mid-Cretaceous, covering about one-third of the land area. Toward the end of the Cretaceous, there was a drop in sea level, causing land exposure on all continents, more seasonality⁴, and greater extremes between equatorial and polar temperatures. The Earth was getting colder.
About 65 million years ago, at the end of the Cretaceous, a large portion of plant and animal families suddenly went extinct. In this Cretaceous-Tertiary or K-T mass extinction -- K is for Kreide, meaning chalk in German, which describes the chalky sediment⁵ layer from that time; T is for Tertiary, the next geologic⁶ period -- all land animals over about 55 pounds went extinct, as did many smaller organisms. The K-T extinction eliminated the dinosaurs⁷, some families of birds and marsupial⁸ mammals, many families of bony fishes, snails⁹, sponges, sea urchins¹⁰ and others. This catastrophe¹¹ eventually led to the Age of Mammals.
There are a lot of theories about why this K-T (Cretaceous-Tertiary) extinction occurred, but a widely accepted theory (proposed in 1980 by physicist¹² Luis Alvarez and his son Walter Alvarez, a geologist), is that an asteroid¹³ 4~9 miles (6~15 km) in diameter hit the Earth about 65 million years ago. The impact would have penetrated¹⁴ the Earth's crust, scattering¹⁵ dust debris¹⁶ into the atmosphere, and causing huge fires (generated by hot debris thrown from the crater¹⁷ tsunamis¹⁸, severe storms with high winds and highly acid rain, seismic¹⁹ activity, and perhaps even volcanic activity. The impact could have caused chemical changes in the Earth's atmosphere, increasing concentrations of sulfuric acid and fluoride compounds. The heat from the impact's blast wave would have incinerated all the life forms in its path. The dust and debris thrust into the atmosphere would have blocked most of the sunlight for months, and lowered the temperature globally.
Those organisms that could not adapt to the temperature and light changes would die out. Since plants' energy is derived²⁰ from the sun, they would likely be the first to be affected²¹ by changes in climate. As plants died out, the Earth's oxygen levels may well have dramatically decreased, both on land and in the oceans, suffocating²² those organisms which were unable to cope with the lower oxygen levels.
Major changes in the food chain would result from all of these environmental upheavals²³. The herbivores (plant eaters) who ate those plants would starve soon after the plants died. Then, at the top of the food chain, the carnivores (meat eaters), having lost their prey²⁴, would have to eat each other, and eventually die out.

1 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

2 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

3 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

4 seasonality   

季节性

参考例句：

• a high degree of climatic seasonality 明显的季节性气候变化
• Confinement. Seasonality of tourist trade, animals often 'contracted' to work. 限制，在旅游旺季时，动物们通常都得被迫“上工”。 来自互联网

5 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

6 geologic   

adj.地质的

参考例句：

• The Red Sea is a geologic continuation of the valley.红海就是一个峡谷在地质上的继续发展。
• Delineation of channels is the first step of geologic evaluation.勾划河道的轮廓是地质解译的第一步。

7 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》

8 marsupial   

adj.有袋的，袋状的

参考例句：

• Koala is an arboreal Australian marsupial.考拉是一种澳大利亚树栖有袋动物。
• The marsupial has been in decline for decades due to urban sprawl from car accidentsdog attacks.这种有袋动物其数量在过去几十年间逐渐减少,主要原因是城市的扩张、车祸和狗的袭击。

9 snails   

n.蜗牛；迟钝的人；蜗牛( snail的名词复数 )

参考例句：

• I think I'll try the snails for lunch—I'm feeling adventurous today. 我想我午餐要尝一下蜗牛——我今天很想冒险。 来自《简明英汉词典》
• Most snails have shells on their backs. 大多数蜗牛背上有壳。 来自《简明英汉词典》

10 urchins   

n.顽童( urchin的名词复数 )；淘气鬼；猬；海胆

参考例句：

• Some dozen barefooted urchins ganged in from the riverside. 几十个赤足的顽童从河边成群结队而来。 来自《简明英汉词典》
• People said that he had jaundice and urchins nicknamed him "Yellow Fellow." 别人说他是黄胆病，孩子们也就叫他“黄胖”了。 来自汉英文学 - 中国现代小说

11 catastrophe   

n.大灾难，大祸

参考例句：

• I owe it to you that I survived the catastrophe.亏得你我才大难不死。
• This is a catastrophe beyond human control.这是一场人类无法控制的灾难。

12 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

13 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

14 penetrated   

adj. 击穿的，鞭辟入里的 动词penetrate的过去式和过去分词形式

参考例句：

• The knife had penetrated his chest. 刀子刺入了他的胸膛。
• They penetrated into territory where no man had ever gone before. 他们已进入先前没人去过的地区。

15 scattering   

n.[物]散射；散乱，分散；在媒介质中的散播adj.散乱的；分散在不同范围的；广泛扩散的；（选票）数量分散的v.散射(scatter的ing形式)；散布；驱散

参考例句：

• The child felle into a rage and began scattering its toys about. 这孩子突发狂怒，把玩具扔得满地都是。 来自《简明英汉词典》
• The farmers are scattering seed. 农夫们在播种。 来自《简明英汉词典》

16 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

17 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

18 tsunamis   

n.海啸( tsunami的名词复数 )

参考例句：

• Our oceans are alive with earthquakes, volcanoes, and more recently, tsunamis. 海中充满着地震、火山，包括最近发生的海啸。 来自常春藤生活英语杂志-2006年2月号
• Please tell me something more about tsunamis! 请您给我讲讲海啸吧！ 来自辞典例句

19 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

20 derived   

vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取

参考例句：

• Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
• He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》

21 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

22 suffocating   

a.使人窒息的

参考例句：

• After a few weeks with her parents, she felt she was suffocating.和父母呆了几个星期后，她感到自己毫无自由。
• That's better. I was suffocating in that cell of a room.这样好些了，我刚才在那个小房间里快闷死了。

23 upheavals   

突然的巨变( upheaval的名词复数 )； 大动荡； 大变动； 胀起

参考例句：

• the latest upheavals in the education system 最近教育制度上的种种变更
• These political upheavals might well destroy the whole framework of society. 这些政治动乱很可能会破坏整个社会结构。

24 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。