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1、托福阅读tpo Desert Formation 沙漠的形成原题解析阅读原文： The deserts, which already occupy approximately a fourth of the Earths land surface, have in recent decades been increasing at an alarming pace. The expansion of desertlike conditions into areas where they did not previously exist is called desertification. It
2、 has been estimated that an additional one-fourth of the Earths land surface is threatened by this process. 沙漠已经占据了地球陆地面积约四分之一，而且最近几十年正以惊人的速度扩张。沙漠化是指类似沙漠的环境漫延到原本并非沙漠的区域。据估计，地球表面另外四分之一的地方正面临沙漠化威胁。 Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the sub
3、sequent accelerated erosion of the soil by wind and water. In some cases the loose soil is blown completely away, leaving a stony surface. In other cases, the finer particles may be removed, while the sand-sized particles are accumulated to form mobile hills or ridges of sand. 沙漠化主要通过以下过程实现：首先自然植被不断
4、减少，随后风力和雨水加速了土壤的腐蚀。有的时候松散的土壤全部被风刮走，留下石质化的表层；其它情况下细小的沙粒可能会被吹走，而正常沙粒大小的砂子不断堆积，从而形成移动的沙丘或者沙脊。 Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soils ability to absorb substantial quantities of water. The impact of raindrops on the loose soil t
5、ends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration. Water absorption is greatly reduced; consequently runoff is increased, resulting in accelerated erosion rates. The gradual drying of the soil caused by i
6、ts diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established. 即便是在保留了土壤表层的区域，植被减少也已成为土壤大量吸取地下水的能力下降的典型因素。雨水对松散土壤的冲击会把细小的粘土颗粒冲到土壤空隙中，封闭 了土壤并降低土地表层水的渗透率。地表对水的吸收急剧减少，大量水资源流失，因此土壤的腐蚀率也随即增加。地表吸收水分的能力进一步弱化使得土壤越发干 燥，导致植
7、被的进一步流失，于是便形成了土壤沙漠化的恶性循环。 In some regions, the increase in desert areas is occurring largely as the result of a trend toward drier climatic conditions. Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years. The process may be accelerated
8、 in subsequent decades if global warming resulting from air pollution seriously increases. 在一些地方，沙漠面积的扩大很大程度上归因于干燥的气候条件。在过去的几千年里，不断增加的温室效应使得一些地方干旱问题愈发严重。倘若空气污染带来的温室效应继续恶化，沙漠化进程会在未来数十年内加速实现。 There is little doubt, however, that desertification in most areas results primarily from human activities rat
9、her than natural processes. The semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures. Expanding populations are subjecting the land to increasing pressures to provide them with food and fuel. In
10、wet periods, the land may be able to respond to these stresses. During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity, and desertification results. 然而，可以肯定的是，大部分地区沙漠化主要都是由于人类活动造成，而非自然条件导致。沙漠边缘的半干旱
11、土地所处的生态平衡环境非常脆弱，环境压力持续增 加，而这些半干旱区域适应环境压力的能力极其有限。人口数量的增加使得人们不断向土地施压，依其提供食物和燃料。在湿润的季节里，土地兴许能够应付这些压 力。但是在干旱的季节里，在沙漠周边的土地上，存在着这样一个十分普遍的现象：人类对土地施加的压力远远超过了土地自身减压的能力，因此最终形成了沙漠。 Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing
12、, firewood gathering, and overirrigation. The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates t
13、he prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion. 导致沙漠化的主要因素有四个：过度种植，过度放牧，过分砍伐，过度灌溉。由于人口密度增加，人们对粮食作物的种植已经扩展到日益干燥的区域进行。这些区域 很有可能经常会发生干旱，所以农作物种植失败是很正常的事情。大多数农作物的种植需要事先移除天然植被，而农作物欠收后又会留下大面积荒地，非常容易被
14、风 力和雨水侵蚀。 The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverizatio
15、n of the soil. This is usually followed by the drying of the soil and accelerated erosion. 在半干旱地区，草坪是主要的天然植被，家畜饲养是当地的一项主要经济活动。在一个地区过量饲养家畜会导致植被覆盖面积减少，土地被大量践踏和碾碎。通常，随之而来的就是土地硬化和加速侵蚀。 Firewood is the chief fuel used for cooking and heating in many countries. The increased pressures of expanding populat
16、ions have led to the removal of woody plants so that many cities and towns are surrounded by large areas completely lacking in trees and shrubs. The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients i
17、s no longer being returned to the land. 在很多国家木材是用来做饭和加热的最主要燃料。人口增加带来的压力促使人们大量砍伐木材，导致许多城市和乡村周围大面积树木和灌木减少。同时人们大量使用烘干的动物排泄物作为替代燃料同样对土壤不利，因为这些珍贵的土壤成分调节剂和植物营养资源将不会再回归至土壤当中。 The final major human cause of desertification is soil salinization resulting from overirrigation. Excess water from irrigation sink
18、s down into the water table. If no drainage system exists, the water table rises, bringing dissolved salts to the surface. The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil. 造成土地沙漠化的最后一个主要人为因素在于人类过度灌溉导致土壤的
19、盐碱化。灌溉多余的水渗透到地下水位。假如没有排水系统的存在，那么地下水位上升，把溶解的盐分带到土壤表面。水分蒸发后，盐分留在了表面，形成白色的地壳层，这一地壳层阻止了空气和水接触地底下的土壤。 The extreme seriousness of desertification results from the vast areas of land and the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process
20、. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form. In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover-crop planting may make it possible to reverse the present deteriora
21、tion of the surface. 沙漠化问题异常严重，这是因为有佷广阔的地区和数量庞大的人群都受到了沙漠化的影响，而且要想逆转沙漠化的进程甚至减缓沙漠化的速度都面临着巨大的困难。 一旦土壤被侵蚀，需要再经过几百到上千年的时间才会产生新的土壤。那些大量土壤仍保存完好的地方，亟需一个严谨而有力的保护政策和植被覆盖计划来保护现有 土地。 第1题： The word threatened in the passage is closest in meaning to A：Restricted B：Endangered C：Prevented D：Rejected 解析： threatened
22、受到威胁的，很容易选出B选项，endangered, 使危险。依据上下文，前句说什么是desertification, 本句说还有14的土地被这种过程如何，也很容易猜出选项。 第2题： According to paragraph 3, the loss of natural vegetation has which of the following consequences for soil? A：Increased stony content B：Reduced water absorption C：Increased numbers of spaces in the soil D：Red
23、uced water runoff 解析： This is a Factual Information question asking for specific information that can be found in paragraph 3. The correct answer is choice 2, reduced water absorption. The paragraph explicitly states that the reduction of vegetation greatly reduces water absorption. Choice 4, reduce
24、d water runoff, explicitly contradicts the paragraph, so it is incorrect. The spaces in the soil are mentioned in another context: the paragraph does not say that they increase, so choice 3 is incorrect. The paragraph does not mention choice 第3题： The word delicate in the passage is closest in meanin
25、g to A：Fragile B：Predictable C：Complex D：Valuable 解析： This is a Vocabulary question. The word being tested is delicate. It is highlighted in the passage. The correct answer is choice 1, fragile, meaning easily broken. Delicate has the same meaning as fragile. 第4题： According to paragraph 5, in dry pe
26、riods, border areas have difficulty A：Adjusting to stresses created by settlement B：Retaining their fertility after desertification C：Providing water for irrigating crops D：Attracting populations in search of food and fuel 解析： 根据dry period 定位本段末句，说在沙漠边缘典型的干旱期，对土地的压力经常远远超过土读弱化的能力，从而导致沙漠化。并且前句说，在湿润季节，
27、土地或许能回应这些压力。前后对比可知干旱期不能回应这些压力。 A 正确，本句和前句内容概括。 B错，沙漠化之后的结果没有提到。 C错，没有提到。 D错，没有提到。 第5题： The word progressively in the passage is closest in meaning to A：Openly B：Impressively C：Objectively D：Increasingly 解析： progressively, 由词跟gress走和前缀pro向前可知词义大致是进步的，前进的，增加的。D正确。 A公开的，B印象深刻的，C客观的都不对。 第6题： According t
28、o paragraph 6, which of the following is often associated with raising crops? A：Lack of proper irrigation techniques B：Failure to plant crops suited to the particular area C：Removal of the original vegetation D：Excessive use of dried animal waste 解析： This is a Factual Information question asking for
29、 specific information that can be found in paragraph 6. The correct answer is choice 3, removal of the original vegetation. Sentence 4 of this paragraph says that the raising of most crops necessitates the prior removal of the natural vegetation, an explicit statement of answer choice 3. Choice 1, l
30、ack of proper irrigation techniques, is incorrect because the paragraph mentions overirrigation as a cause of desertification. No irrigation techniques are discussed. Choices 2 and 4, failure to plant suitable crops and use of animal waste, are not discussed. 第7题： The phrase devoid of in the passage
31、 is closest in meaning to A：Consisting of B：Hidden by C：Except for D：Lacking in 解析： devoid of 缺乏，很容易选出D。根据上下文，本句后段说，and susceptible to wind and water erosion. 该段读懂也能猜出词义。 A 组成，B隐藏，C除外都不对。 第8题： According to paragraph 9, the grounds absorption of excess water is a factor in desertification because it
32、can A：Interfere with the irrigation of land B：Limit the evaporation of water C：Require more absorption of air by the soil D：Bring salts to the surface 解析： 根据absorption of excess water定位，找到excess water from irrigation sinks into the water table. 后句提到，bringing dissolved salts to the surface. 可知D正确。 A
33、错，没有提到。 B错，没有提到。 C错，没有提到。 第9题： All of the following are mentioned in the passage as contributing to desertification EXCEPT A：Soil erosion B：Global warming C：Insufficient irrigation D：The raising of livestock 解析： This is a Negative Factual Information question asking for specific information that can
34、 be found in the passage. Choice 3, insufficient irrigation, is the correct answer. Choice 1, soil erosion, is explicitly mentioned in paragraph 2 as one of the primary causes of desertification, so it is not the correct answer. Choice 2, global warning, is mentioned as a cause of desertification in
35、 paragraph 4, so it is incorrect. Choice 4, raising of livestock, is described in paragraph 7 as another cause of desertification, so it is incorrect. The passage includes excessive irrigation as a cause of desertification, but not its opposite, insufficient irrigation, so that is the correct answer
36、. 第10题： Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information. A：Desertification is a significant problem because it is so hard to reverse and affects
37、large areas of land and great numbers of people. B：Slowing down the process of desertification is difficult because of population growth that has spread over large areas of land. C：The spread of deserts is considered a very serious problem that can be solved only if large numbers of people in variou
38、s countries are involved in the effort. D：Desertification is extremely hard to reverse unless the population is reduced in the vast areas affected. 解析： 原句含有一个弱因果关系results from. 沙漠化的严重性来自3个方面：受影响土地面积大，受影响人口多，恢复困难。 A正确，只改变了原句叙述顺序。 B错，改变了因果关系。 C错，增加了条件关系。 D错，增加了条件关系。 第11题： It can be inferred from the p
39、assage that the author most likely believes which of the following about the future of desertification? A：Governments will act quickly to control further desertification. B：The factors influencing desertification occur in cycles and will change in the future. C：Desertification will continue to incre
40、ase. D：Desertification will soon occur in all areas of the world 解析： 推理题，由整篇文章，尤其是末段可以推断出作者对于沙漠化持悲观态度，C与此态度一致。 A不能推出，末段末句说，严格的政策可能may 改变沙漠化进程，但没有A确定推断。 B错，3段提到有可能恶性循环，但不能确定改变。 D错，该选项过于悲观。文章首段提到additional one-fourth of the Earths land surface, 但没有说全部地区 第12题： Look at the four squares that indicate whe
41、re the following sentence can be added to the passage. Where would the sentence best fit? This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing. 解析： 插入句说，特定地区对于牲畜的经济依赖导致大片土地易于被过度放牧。由B位置后句consequence推断，正好和插入句构成因果关系。 第13题： Directions: An introduct
42、ory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are
43、 minor ideas in the passage. This question is worth 2 points. Many factors have contributed to the great increase in desertification in recent decades. A. Growing human populations and the agricultural demands that come with such growth have upset the ecological balance in some areas and led to the
44、spread of deserts. B. As periods of severe dryness have become more common, failures of a number of different crops have increased. C. Excessive numbers of cattle and the need for firewood for fuel have reduced grasses and trees, leaving the land unprotected and vulnerable. D. Extensive irrigation w
45、ith poor drainage brings salt to the surface of the soil, a process that reduces water and air absorption. E. Animal dung enriches the soil by providing nutrients for plant growth. F. Grasses are generally the dominant type of natural vegetation in semiarid lands. 解析： This is a Prose Summary question. It is completed correctly below. The correct choices are 1, 3, and 4. Choices 2, 5, and 6 are therefore incorrect. 答案： 第1题：B 第2题：B 第3题：A 第4题：A 第5题：D 第6题：C 第7题：D 第8题：D 第9题：C 第10题：A 第11题：C 第12题：B 第13题：ACD
