comets托福阅读？天文类Surface Fluids on Venus and Earth 参考阅读：A fluid is a substance， such as a liquid or gas，那么，comets托福阅读？一起来了解一下吧。

TPO讲comets

托福阅读：

小行星对恐龙灭绝的影响。一个科学家发现土层中里有很多Ir元素，而Ir元素在地球上少见，因此推断是小行星导致了恐龙灭绝。后面又说了小行星使得气温降低，空气化学组成改变等等也导致恐龙的灭绝，但是一些小的啮齿类动物则存活了下来。

托福阅读相关背景：

参考文章：Meteorite Impact and Dinosaur Extinction

Extinction of the Dinosaurs

Mass Extinctions

背景知识：

Impact event

Biospheric effects

The effect of impact events on the biosphere has been the subject of scientific debate. Several theories of impact related mass extinction have been developed. In the past 500 million years there have been five generally accepted, major mass extinctions that on average extinguished half of all species. One of the largest mass extinction to have affected life on Earth was in the Permian-Triassic, which ended the Permian period 250 million years ago and killed off 90% of all species; life on Earth took 30 million years to recover. The cause of the Permian-Triassic extinction is still matter of debate with the age and origin of proposed impact craters, i.e. the Bedout High structure, hypothesized to be associated with it are still controversial. The last such mass extinction led to the demise of the dinosaurs and coincided with a large meteorite impact; this is the Cretaceous–Paleogene extinction event (also known as the K–T or K–Pg extinction event); This occurred 66 million years ago. There is no definitive evidence of impacts leading to the three other major mass extinctions.

In 1980, physicist Luis Alvarez; his son, geologist Walter Alvarez; and nuclear chemists Frank Asaro and Helen V. Michael from the University of California, Berkeley discovered unusually high concentrations of iridium in a specific layer of rock strata in the Earth's crust. Iridium is an element that is rare on Earth but relatively abundant in many meteorites. From the amount and distribution of iridium present in the 65-million-year-old "iridium layer", the Alvarez team later estimated that an asteroid of 10 to 14 km (6 to 9 mi) must have collided with the earth. This iridium layer at the Cretaceous–Paleogene boundary has been found worldwide at 100 different sites. Multidirectionally shocked quartz (coesite), which is only known to form as the result of large impacts or atomic bomb explosions, has also been found in the same layer at more than 30 sites. Soot and ash at levels tens of thousands times normal levels were found with the above.

Anomalies in chromium isotopic ratios found within the K-T boundary layer strongly support the impact theory. Chromium isotopic ratios are homogeneous within the earth, therefore these isotopic anomalies exclude a volcanic origin which was also proposed as a cause for the iridium enrichment. Furthermore the chromium isotopic ratios measured in the K-T boundary are similar to the chromium isotopic ratios found in carbonaceous chondrites. Thus a probable candidate for the impactor is a carbonaceous asteroid but also a comet is possible because comets are assumed to consist of material similar to carbonaceous chondrites.

Probably the most convincing evidence for a worldwide catastrophe was the discovery of the crater which has since been named Chicxulub Crater. This crater is centered on the Yucatán Peninsula of Mexico and was discovered by Tony Camargo and Glen Pentfield while working as geophysicists for the Mexican oil companyPEMEX. What they reported as a circular feature later turned out to be a crater estimated to be 180 km (110 mi) in diameter. Other researchers would later find that the end-Cretaceous extinction event that wiped out the dinosaurs had lasted for thousands of years instead of millions of years as had previously been thought. This convinced the vast majority of scientists that this extinction resulted from a point event that is most probably an extraterrestrial impact and not from increased volcanism and climate change (which would spread its main effect over a much longer time period).

Recently, several proposed craters around the world have been dated to approximately the same age as Chicxulub — for example, the Silverpit crater in the United Kingdom, the Boltysh crater in Ukraine and the Shiva crater near India. This has led to the suggestion that the Chicxulub impact was one of several that occurred almost simultaneously, perhaps due to a disrupted comet impacting the Earth in a similar manner to the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994; however, the uncertain age and provenance of these structures leaves the hypothesis without widespread support.

It was the lack of high concentrations of iridium and shocked quartz which has prevented the acceptance of the idea that the Permian extinction was also caused by an impact. During the late Permian all the continents were combined into one supercontinent named Pangaea and all the oceans formed one superocean,Panthalassa. If an impact occurred in the ocean and not on land at all, then there would be little shocked quartz released (since oceanic crust has relatively little silica) and much less material.

Although there is now general agreement that there was a huge impact at the end of the Cretaceous that led to the iridium enrichment of the K-T boundary layer, remnants have been found of other, smaller impacts, some nearing half the size of the Chicxulub crater, which did not result in any mass extinctions, and there is no clear linkage between an impact and any other incident of mass extinction.

Paleontologists David M. Raup and Jack Sepkoski have proposed that an excess of extinction events occurs roughly every 26 million years (though many are relatively minor). This led physicist Richard A. Muller to suggest that these extinctions could be due to a hypothetical companion star to the Sun calledNemesis periodically disrupting the orbits of comets in the Oort cloud, and leading to a large increase in the number of comets reaching the inner solar system where they might hit Earth. Physicist Adrian Melott and paleontologist Richard Bambach have more recently verified the Raup and Sepkoski finding, but argue that it is not consistent with the characteristics expected of a Nemesis-style periodicity.

托福tpo63阅读答案

在目前浩浩荡荡的托福大军中，大家都在纠结着一个问题：做托福阅读文章时，要不要先把文章整体读一遍?就这个问题而言，我们的“托儿”们不得不被倚天剑劈成两大帮派：读与不读。下面将会为大家解释为什么要在做托福阅读题目之前要先将文章整体阅读一遍。

托福阅读做题要先整体的读一遍

一、托福阅读考试界面的设置

参加过考试的或是用模考软件做过练习的“托儿”们都清晰的记得：当一篇托福阅读文章问题出现的之前，一定是先以整篇文章的形式出现的，左边并没有显示题目，只有将文章右边的滚动轴拉至最低端，界面才会自动转换为我们做题的界面，即左边是问题，右边是对应的文章。

那么，我们就分析一下为什么ETS有这样的设置?ETS有什么样的意图?ETS想让考生怎么做?这样的设置显而易见ETS是希望考生们可以在做题前将文章大致整体看一遍。就ETS出题的严谨性和科学性而言，这样的设置毋庸置疑是帮助考生提高其做题的速度和正确率的。

我们已经分析完出题人的意图，那么接下来就是要解答界面设置导致的整体阅读有哪些好处，如何帮助考生们答题，如何提高做题速度和正确率的。

二、整体阅读托福阅读文章对summary questions的帮助

对于托福阅读速度不高，英语水平中等或中等以下的“托儿”们普遍反映的一个问题就是：没有时间做最后的summary questions，或是做summary questions的时候不知道到哪里找答案或是正确率低。

tpo63阅读答案第二篇

所以彗星应该长走了,对吗?我的意思是,为什么哈雷的仍然是那里?在四个半年。这怎么可能?嗯,答案是,这颗彗星并不总是在这样短暂周期轨道,因为一旦一颗彗星进入一个轨道,这使它未来在接近太阳相当频繁。嗯,那颗彗星可能无法一起太久。所以这种周期性轨道只是一个阶段的生活acomet阶段,只是最后的分手我们之前所看到的彗星做,要向太阳,然后回来,撕成碎片。

托福阅读真题100篇pdf

including，这是个固定搭配吧==！你要是用included就要放那个被修饰的名词后面啊

from materials in，这句是说小行星可能是来自于一个行星的碎片，这碎片是从一个行星上面分离出来的，或者小行星是之前彗星的核心。。。我语文不好，大概这个意思

up，你看C后面那个它用了个down,所以这里对应用up

我记得这几句好像是托福阅读里面的句子。。

TPO 63 托福阅读第2篇structure

在托福阅读中，词汇是最重要的问题，而这个也主要考平时的积累，那么接下来就和来看看托福阅读100个核心词汇。

1. a couple of 两三个，几个

Although he thought of the key idea in 1951， the first maser was not completed until a couple of years later.

2. account for 解释

Variations of clay composition and the temperatures at which they are fired account for the differences in texture and appearance.

3. adapt to 使适应于

They have been able to adapt to ecological changes.

4. adorn with sth 用…装饰

Some pots were adorned with incised or stamped decorations.

5. appeal to 吸引

Publishing literature consisting of exciting stories that would appeal to both children and adults

6. apply to 适用于

Ethological theory began to be applied to research on children in the 1960’s.

7. at best 充其量，最多

Hunting is at best a precarious way of procuring food， even when the diet is supplemented with seeds and fruits.

8. at intervals 相隔一定距离

However， at intervals of 10 to 100 years， these glaciers move forward up to 100 times faster than usual.

9. at the expense of sth 在损害…的情况下

A multitude of microorganisms make their livings directly at the expense of other creatures.

10. at the height of sth 在…最鼎盛时期

The violin had reached the height of its popularity by the middle of the eighteenth century.

11. back and forth 来回地

They then spiral back and forth between the Earth＇s magnetic poles very rapidly.

12. be absent from 缺席，不在

Lacking the right to vote and absent from the seats of power， women line were not considered an important force in history.

13. be capable of 能…的

Many animals are capable of using objects in the natural environment as rudimentary tools.

14. be characterized by 以…为特征

The nervous system of vertebrates is characterized by a hollow， dorsal nerve cord that ends in the head region as an enlargement， the brain.

15. be composed of 由…组成

Ocean life is primarily composed of plants.

16. be concerned with 与某事物有关

Ethnology is concerned with the study of adaptive， or survival， value of behavior and its Evolutionary history.

17. be distinct from 与…不同

Jupiter and the other giant planets are of a low-density type quite distinct from the terrestrial planets

18. be essential to 对…不可缺少

Public performance is essential to verbal art.

19. be exposed to 使接触，使遭受

Body contact reduces the surface area exposed to the cold air.

20. be far from 离…很远，根本不是

But far from being random， molt is controlled by strong evolutionary forces that have established an optimal time and duration.

21. be hostile to 极不友好的，极厌恶的

Ocean bottom is a hostile environment to humans

22. be regarded as 被认为是

Humanity＇s primal efforts to systematize the concepts of size， shapes， and number are usually regarded as the earliest mathematics.

23. be related to 与…有关的，相联系的

Why is dancing closely related to popular music in the United States？

24. be responsible for 对…负责

In fact， nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce.

25. be sensitive to 对…敏感的

Ants can be extremely sensitive to these signals.

26. be subjected to 经历，遭受

Oil is formed when organic material trapped in sediments is slowly buried and subjected to increased temperatures and pressures， transforming it into petroleum.

27. be superior to 优越于

Natural vitamins are superior to synthetic ones

28. be traced to 找出根源

The ancestry of the piano can be traced to the early keyboard instruments of the fifteenth and sixteenth centuries.

29. be/become aware of 意识到，认识到

People became aware of the new service by word of mouth or newspaper advertisements.

30. be/become/get accustomed to 习惯于

In the harsh environment of northern Europe， Scandinavian women had been accustomed to practicing forms of shifting cultivation， and they immediately understood Native American horticulture.

31. be/become/get involved in 与…有关联的

Two distinct processes are involved in molting.

32. benefit from 从…中受益

Students benefit from schools， which require long hours and homework.

33. break down 分解

All of these forces slowly break down the Earth＇s exposed rocky crust into smaller and smaller pieces that eventually become clay.

34. by far 到目前为止

Marine sediment is by far the most important environment for the preservation of fossils.

35. by means of 通过，凭借

The topic of the passage is developed primarily by means of Adividing the discussion into two major areas.

36. by virtue of 由于

Many are uninhabitable， by virtue of their small size and particular characteristics

37. confine to 限制在一定范围之内

The delivery service was at first confined to cities.

38. conform to 符合

Parks should be designed to conform to the topography of the area

39. contribute to 有贡献，有助于

Transportation contributed to the development and maintenance of trade.

40. cope with 对付

Under certain circumstance the human body must cope with gases at greater-than-normal atmospheric pressure.

41. date back to 始于

In the United States， rent controls date back to at least World War II.

42. depend on 依靠

The gulls depend on the falcons for protection.

43. deprive sb/sth of sth 剥夺..某事物

Plant stems die when deprived of water.

44. derive from 获得，起源于

Babies obviously derive pleasure from sound input.

45. due to 由于，因为

Due to their dense structure， iron meteorites have the best chance of surviving an impact， and most are found by farmers plowing their fields.

46. evolve from/out of 从...进化来，从…发展来

The one most widely accepted today is based on the assumption that drama evolved from ritual.

47. extract from 提取

It turns out that some fossils can be extracted from these sediments by putting the rocks in an acid bath.

48. feed on 以…为食物

Predators are animals that capture and feed on other animals.

49. focus on 集中（注意力）于

They focus on the meaning of their parents＇ words.

50. get rid of 处理掉

Atoms or molecules get rid of excess energy by themselves， without any outside intervention.

51. give access to 向…开放

To connect the pueblos and to give access to the surrounding tableland， the architects laid out a system of public roads with stone staircases for ascending cliff faces.

52. give birth to 使诞生，引起

Most insects lay eggs， but some give birth to live young.

53. give off 发散，发出

If Jupiter were larger， it would give off much less heat.

54. give rise to 引起，导致

The musical Renaissance was too short to give rise to a new musical style.

55. go beyond 超过，越过

An interviewer can go beyond written questions and probe for a subject＇s underlying feelings and reasons.

56. go out of business 停业，关门

The shop went out of business.

57. have nothing to do with 与…无关

A species’ survival may have nothing to do with its ability or inability to adapt.

58. impart to 传授给

They functioned as sanctuaries where the elders impart tribal lore to the younger generation.

59. impose on 强加于

New regulations were imposed on nontraditional education.

60. in common 共同

No two comets ever look identical， but they have basic features in common.

61. in favor of 赞同，支持

The artist was in favor of a traditional style of painting.

62. in quantity 大量，大批

There were also a number of poor-quality figurines and painted pots produced in quantity by easy， inexpensive means.

63. in season 当季

Before the mid-nineteenth century， people in the United States ate most foods only in season.

64. in spite of 尽管，任凭

In spite of problems with their condition， restoration， and preservation many panel paintings have survived.

65. in the absence of 在缺乏…的情况下

The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities.

66. in view of 由于

In view of the rate at which the radio sources emit energy， they should disappear in a few million years.

67. instead of 代替

Instead of working with light， however， he worked with microwaves.

68. invest in 投资

He started to invest in the town’s cultural development.

69. lead to 导致，引起

In fact， there is wide agreement that it is the rate of change humans are inflicting， even more than the changes themselves that will lead to biological devastation.

70. leave out 排除

Explanations of animal behavior that leave out any sort of consciousness at all and ascribe actions entirely to instinct leave many questions unanswered.

71. off the mark 不正确

This analogy is not far off the mark.

72. on behalf of 代表

Satire serves to prod people into an awareness of truth though rarely to any action on behalf of truth.

73. on the basis of 在…的基础上

Antoine Lavisher， on the basis of careful experimentation， was led to propose a different theory of burning

74. owing to 由于，因为

Marine sediment is by far the most important environment for the preservation of fossils， owing to the incredible richness of marine life.

75. perceive sth as sth 认为

Although art deco in its many forms was largely perceived as thoroughly modern， it was strongly influenced by the decorative arts movements that immediately preceded it.

76. pick up 学会

Adults make it as easy as they can for babies to pick up a language by exaggerating such cues.

77. put off 推迟

Some tasks could not be done in the winter， other had to be put off during harvest time.

78. regardless of 不顾

Ultimately， literature is aesthetically valued， regardless of language， culture， or mode of presentation.

79. result from 因..而产生

Most functions result from the needs of the local area and of the surrounding.

80. result in 结果，导致

The upward movement of fieldstones should result in pure soil.

81. set about 开始，动手

African American artists of this period set about creating a new portrayal of themselves and their lives in the United States.

82. set aside 留下将来用

Certain parts of town were restricted to residential use， while others were set aside for industrial or commercial development.

83. so far 到目前为止

The Paris Exhibition of 1889 included both the widest span and the greatest height achieved so far.

84. sort out 把…分类

Clay particles are sorted out by size and weight.

85. spring up 涌现

In the early colonial day in North America， small cities sprang up along the Atlantic Coastline.

86. stem from 起源于

It can be argued that much of New York City’s importance stems from its early and continuing advantage of situation.

87. stretch out 伸展，伸出

The residues from these explosions left huge black marks on the face of Jupiter， some of which have stretched out to form dark ribbons.

88. strive for 为…而奋斗

As they began to strive for social and cultural independence，their attitudes toward themselves changed.

89. take account of sth./take sth into account 考虑到

Artists are recognizing the distinction between public and private spaces， and taking that into account when executing their public commissions.

90. take advantage of 利用

Many families could take advantage of previously unavailable fruits， vegetables， and dairy products to achieve more varied fare.

91. thanks to 由于

kiwis smell out earthworms thanks to nostrils located at the tip of their beaks.

92. to some extent 某种程度上

Their attitudes toward themselves changed， and， to some extent， other segments of American society began to change their attitudes toward them.

93. turn out 结果是，证明是

Some potash was exported from Maine and New Hampshire in the seventeenth century， but the market turned out to be mainly domestic.

94. usher in 宣告…的来临

Autumn could be ushered in by severe frost.

95. wear away 磨损

Natural forces wear away the Earth＇s crust

96. wipe out 消灭，肃清

Entire crops can be wiped out by fungal attacks both before and after harvesting.

97. with respect to 在…方面

The year 1850 may be considered the beginning of a new epoch in America art， with respect to the development of watercolor painting.

98. with the advent of 随着…的出现

With the advent of high-resolution radio interferometers during the late 1970＇s， part of the answer became clear.

99. with the aid of 借助于

It is now taught with the aid of computers.

100. with the exception of 除..以外

With the exception of printing patterns directly onto the cloth， whether by block， roller， or screen， all of these are based on dyeing； that is， the immersion of the fabric in a dye bath.

以上就是comets托福阅读的全部内容，托福阅读：小行星对恐龙灭绝的影响。一个科学家发现土层中里有很多Ir元素，而Ir元素在地球上少见，因此推断是小行星导致了恐龙灭绝。后面又说了小行星使得气温降低，空气化学组成改变等等也导致恐龙的灭绝，但是一些小的啮齿类动物则存活了下来。内容来源于互联网，信息真伪需自行辨别。如有侵权请联系删除。