开始正式内容之前，我们要强调的是，话题内容一定要进行记忆。不进行必要的记忆是不能形成脑中的“资源”的。记忆就是要你复习。复习不以记忆为目标也是不对的。
 
乔布斯曾经非常经典地把“温故而知新”的必要性paraphrase了一遍：You can only connect the dots looking backwards.

 

总之要看文章，要复习，要记忆。我们将就托福阅读中的一个常考话题进行处理。这个话题就是“恐龙灭绝”。

这话题有多常考呢？TPO中，有5篇文章与“恐龙”有关。这5篇中又有4篇与“恐龙灭绝”直接相关。他们是：

 

TPO08B - Extinction of the Dinosaurs
TPO15B - Mass Extinction
TPO33C - Extinction Episodes of the Past
TPO42B - Explaining Dinosaur Extinction
 

TPO48B仅同“恐龙”有关。这篇挺搞笑的。先按下不表。
 

我们已经把这4篇“恐龙灭绝”话题的文章定位好了，那么一起来回顾一下他们的内容。这些内容可以通过一些关键词进行串联。也就是乔大爷所说的connecting the dots中的dots啦。

 

个关键词：Iridium

铱元素是一种很有意思的元素，它的原子序数（atomic number）是77（原子核中有77个质子proton）。
 
一家运营海事卫星电话业务的公司（业界鼎鼎有名）本打算发射77颗通信卫星到近地轨道（low Earth orbit）——77正好是铱元素质子的数目，所以这家公司取了个炫酷的名字，“铱星公司（Iridium Communications）”。

石油钻探公司，航海旅行家，以及美国国防部，都使用这家公司提供的卫星电话服务。

关于铱元素的名字其实还可以多说一说。

 

铱溶解于盐酸时会产生彩虹般的色彩。“彩虹般的”叫 iridescent。

眼睛的虹膜，叫 iris，色彩丰富哦。

 

希腊神话中，Iris 是众神的信使，彩虹女神。

彩虹“五彩缤纷”的特点解释了为什么由“彩虹女神”Iris 我们会看到 Iridescent（五彩缤纷的）、iris（虹膜）、Iridium（铱元素——溶解于盐酸会呈现“五彩缤纷”色彩）这一众单词了。

 

花了这么多篇幅讲铱元素，合理不？合理。

 

▲ 出自TPO08B

▲ 出自TPO08B

▲ 出自TPO15B

▲ 出自TPO33C

以上4个段落都是原生态的TPO文章选段。而且都是围绕铱元素而写的。铱元素这一独特存在关键性地解释了为什么包括恐龙在内的那么多生物会迅速灭绝。

第二个关键词：Cretaceous

白垩纪中，恐龙们延续了他们对地球的主宰，但白垩纪晚期恐龙神秘而突然地灭绝了。
 
“白垩”就是 chalk（白色柔软泥土似的石灰岩，由古老海洋生物的骨骼残骸形成，成分是碳酸钙  calcium carbonate），chalk 另外一个意思大家会比较熟悉——粉笔（不过粉笔的成分是硫酸钙 calcium sulphate）。
 
拉丁文中 creta 表示 chalk，所以 Cretaceous 即“白垩纪”。

 

提到白垩纪和恐龙灭绝，TPO文章中会频繁出现的一个相关概念叫 the K-T boundary （白垩纪与第三纪的界线）。
 
“T”指的是第三纪（the Tertiary period）。

“K”呢，是德语“白垩纪”一词 Kreidezeit 的首字母，这在42B文章中有交代：

Dinosaurs rapidly became extinct about 65 million years ago as part of a mass extinction known as the K-T event, because it is associated with a geological signature known as the K-T boundary, usually a thin band of sedimentation found in various parts of the world (K is the traditional abbreviation for the Cretaceous, derived from the German name Kreidezeit).（TPO42B）
 
第三纪（Tertiary）包括了新生代的古近纪（Paleogen）和新近纪（Neogene），看下表。

According to one theory, the Age of Dinosaurs ended suddenly 65 million years ago when a giant rock from space plummeted to Earth. Estimated to be ten to fifteen kilometers in diameter, this bolide (either a comet or an asteroid) was traveling at cosmic speeds of 20-70 kilometers per second, or 45,000-156,000 miles per hour.（TPO42B）

 

 

因为其实同白垩纪“紧挨着”的往大了说是第三纪，所以有 the K-T boundary；往小了说是 Paleogene（古近纪），所以 the K-T boundary 又称 the K-Pg boundary  （白垩纪与古近纪的界线）。据维基百科，之前多用前者，现在常用 the K-Pg boundary。

▲ 出自TPO8B

▲ 出自TPO15B

▲ 出自TPO33C

第三个关键词：bolide

According to one theory, the Age of Dinosaurs ended suddenly 65 million years ago when a giant rock from space plummeted to Earth. Estimated to be ten to fifteen kilometers in diameter, this bolide (either a comet or an asteroid) was traveling at cosmic speeds of 20-70 kilometers per second, or 45,000-156,000 miles per hour.（TPO42B）

上面这个句子告诉我们，bolide的两种形式：comet 或是 asteroid。

 

最后一个关键词：Chicxulub
希克苏鲁伯，有人音译成“奇虚乐”，好有末世感。

这是墨西哥的一个地名。科学家们在这里发现了the K-T event 的证据：the Chicxulub crater（希克苏鲁伯陨石坑），见上图。

▲ 出自TPO15B

下面，我们用几句话进行概括这4篇文章的主要内容，附带TPO英文原文及出处。
1、恐龙灭绝是the K-T event的一部分，当时还有很多其他生物灭绝了。the K-T boundary是the K-T event的地质标志。
Dinosaurs rapidly became extinct about 65 million years ago as part of a mass extinction known as the K-T event, because it is associated with a geological signature known as the K-T boundary, usually a thin band of sedimentation found in various parts of the world (K is the traditional abbreviation for the Cretaceous, derived from the German name Kreidezeit).（TPO42B）

 

2、the K-T boundary 实际上是代表两个地质时期的两个岩层之间的一层粘土。
Many plants and animals disappear abruptly from the fossil record as one moves from layers of rock documenting the end of the Cretaceous up into rocks representing the beginning of the Cenozoic (the era after the Mesozoic). Between the last layer of Cretaceous rock and the first layer of Cenozoic rock, there is often a thin layer of clay.（TPO8B）

 

3、通过确定the K-T boundary这薄薄一层粘土中Iridium的含量，科学家觉得能了解灭绝花了多长时间。
Scientists felt that they could get an idea of how long the extinctions took by determining how long it took to deposit this one centimeter of clay and they thought they could determine the time it took to deposit the clay by determining the amount of the element iridium (Ir) it contained.（TPO08B）

 

4、铱元素在地球上的分布特点是：地表很少。金属态的铱大多在地心。
Ir has not been common at Earth’s since the very beginning of the planet’s history. Because it usually exists in a metallic state, it was preferentially incorporated in Earth’s core as the planet cooled and consolidated.（TPO08B）

 

5、不过，某些陨石上有着丰富的铱。陨石今天仍旧会落到地球上。（前两天老师还看到新闻说新疆那有农民家藏着上吨重的陨石，陨星在国际市场卖大价钱的~发财了新疆兄弟）
Ir is found in high concentrations in some meteorites, in which the solar system’s original chemical composition is preserved. Even today, microscopic meteorites continually bombard Earth, falling on both land and sea.（TPO08B）

 

6、K-T boundary当中的铱的含量，据计算，如果是小陨石（当今地球接收的常规体量的陨石） 带来的话，那得要一亿年才积累得了~不过，没有展开细说的其他证据表明，积累的时间并没有花上一亿年。
By measuring how many of these meteorites fall to Earth over a given period of time, scientists can estimate how long it might have taken to deposit the observed amount of Ir in the boundary clay. These calculations suggest that a period of about one million years would have been required. However, other reliable evidence suggests that the deposition of the boundary clay could not have taken one million years. So the unusually high concentration of Ir seems to require a special explanation.（TPO08B）

 

7、所以，科学家认为应该是一块大的小行星（asteroid），带来了K-T boundary中的铱元素，并导致了包括恐龙在内的生物的灭绝。
In view of these facts, scientists hypothesized that a single large asteroid, about 10 to 15 kilometers across, collided with Earth, and the resulting fallout created the boundary clay. Their calculations show that the impact kicked up a dust cloud that cut off sunlight for several months, inhibiting photosynthesis in plants; decreased surface temperatures on continents to below freezing; caused extreme episodes of acid rain; and significantly raised long-term global temperatures through the greenhouse effect. This disruption of food chain and climate would have eradicated the dinosaurs and other organisms in less than fifty years.（TPO08B）

 

末日景象是怎样的？

好几篇文章都有对小行星撞地球这一灾难进行了描述。

TPO08B  阳光被阻断好几个月，因此植物进行不了光合作用，陆地地表温度降到了零度以下，酸雨不断，温室效应导致长期的全球气温上升。
Their (scientists') calculations show that the impact kicked up a dust cloud that cut off sunlight for several months, inhibiting photosynthesis in plants; decreased surface temperatures on continents to below freezing; caused extreme episodes of acid rain; and significantly raised long-term global temperatures through the greenhouse effect.（TPO08B）

 

TPO15B  陨石同地球相撞导致大量尘土进入大气，在细微颗粒物尘埃落定前，遮天蔽日好几年。光合作用水平下降，各种植物生命大规模减少，食草动物先饿死，然后是食肉动物大规模死去。
According to this hypothesis, Earth collided with an asteroid with an estimated diameter of 10 kilometers, or with several asteroids, the combined mass of which was comparable. The force of collision spewed large amounts of debris into the atmosphere, darkening the skies for several years before the finer particles settled. The reduced level of photosynthesis led to a massive decline in plant life of all kinds, and this caused massive starvation first of herbivores and subsequently of carnivores.（TPO15B）

 

TPO33C  大量尘土云包裹住了地球，阻断了太阳辐射抵达地球，使植物光合作用降到了非常低的水平。短期内的影响也许是巨大的海啸和广泛的火灾。一句话，一个灾难引起一系列事件，这一系列事件导致了大规模灭绝。
They believed that this impact generated a thick cloud of dust that enveloped Earth, shutting out much of the incoming solar radiation and reducing plant photosynthesis to very low levels. Short-term effects might have included huge tidal waves and extensive fires. In other words, a series of events arising from a single cataclysmic event caused the massive extinctions.（TPO33C）

 

TPO42B  这次撞击“激起千层浪”，洪水在加勒比地区造成很大的破坏。撞击还在撞击点撞出100立方公里的岩石和岩屑，将这些送上了100公里的高空。大气中的微尘和浓烟造成了核冬天。电脑气候模型显示，气温降到冰点附近，光合作用停止，陆地上和海洋中的植物死去。食物链顶端的恐龙在这之后灭绝。
The impact displaced huge volumes of seawater, causing much flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100 cubic kilometers of rock and debris from the site, which rose to an altitude of 100 kilometers. Most of it fell back immediately, but some of it remained as dust in the atmosphere for months. This material, along with the smoke from the Gres, shrouded Earth, creating a form of nuclear winter. According to computerized climate models, global temperatures fell to near the freezing point, photosynthesis halted, and most plants on land and in the sea died. With the bottom of the food chain destroyed, dinosaurs could not survive.（TPO42B）

 

科学家们在证实小行星撞地球这一理论之前有发表其他的理论。
这些理论大多不充分，当中有些其实很搞笑（我没有不尊重科学家的意思，是的确挺搞笑的）。比如有认为恐龙灭绝是单纯因为气候变化。
（是的，我知道这个不好笑，继续看）

Paleontologists have argued for a long time that the demise of the dinosaurs was caused by climatic alterations associated with slow changes in the positions of continents and seas resulting from plate tectonics.（TPO08B）

There are several hypotheses, including warming or cooling of Earth, changes in seasonal fluctuations or ocean currents, and changing positions of the continents.（TPO15B）

For many years scientists assumed that a cooling of the climate was responsible, with dinosaurs being particularly vulnerable because, like modern reptiles, they were ectothermic (dependent on environmental heat, or cold-blooded).（TPO33C）

 

有认为恐龙灭绝是因为哺乳动物把恐龙蛋都吃掉了，注意，是都吃掉了。（哈哈哈~）

Others have blamed extinction on competition from the mammals, which allegedly ate all the dinosaur eggs-except that mammals and dinosaurs appeared at the same time in the Late Triassic, about 190 million years ago, and there is no reason to believe that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence.（TPO42B）

 

有认为恐龙灭绝是因为消化不良~（大活人不能被尿憋死，大恐龙会被吃的东西？？？哈哈哈）

For example, some have blamed dinosaur extinction on the development of flowering plants, which were supposedly more difficult to digest and could have caused constipation or indigestion-except that flowering plants first evolved in the Early Cretaceous, about 60 million years before the dinosaurs died out. In fact, several scientists have suggested that the duckbill dinosaurs and horned dinosaurs, with their complex battery of grinding teeth, evolved to exploit this new resource of rapidly growing flowering plants.（TPO42B）

 

消化不良引起恐龙灭绝？还记得我们文章前说过TPO48B同“恐龙”有关不？那篇叫Determining Dinosaur Diet ~ 科学家们对恐龙吃什么还真的是有兴趣的。文章里介绍的研究方法特别有意思。
 

大家平时刷阅读题要做好基本的话题分类。分类后，复习像生物、地球物理、文明发展等话题都可以采取我们这里介绍的“恐龙灭绝”话题类似的处理策略：关键词串联文章核心内容。
 
希望这篇文章能对大家备考“恐龙灭绝”话题提供帮助~