TPO2托福阅读Passage1 Desert Formation文本+题目文本+答案解析

Desert Formation

The deserts, which already occupy approximately a fourth of the Earth's 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 has been estimated that an additional one-fourth of the Earth's land surface is threatened by this process.

Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent 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.

Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water. The impact of raindrops on the loose soil tends 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 its diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established.

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 in subsequent decades if global warming resulting from air pollution seriously increases.

There is little doubt, however, that desertification in most areas results primarily from human activities rather 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 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.

Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing, 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 the 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.

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 pulverization of the soil. This is usually followed by the drying of the soil and accelerated erosion.

Firewood is the chief fuel used for cooking and heating in many countries. The increased pressures of expanding populations 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 is no longer being returned to the land.

The final major human cause of desertification is soil salinization resulting from overirrigation. Excess water from irrigation sinks 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.

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. 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 deterioration of the surface.

TPO2托福阅读Passage1题目

Question 1 of 13：The word “threatened ” in the passage is closest in meaning to

A. restricted.

B. endangered.

C. prevented.

D. rejected.

Question 2 of 13：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. Reduced water runoff.

Question 3 of 13：The word “delicate ” in the passage is closest in meaning to

A. fragile.

B. predictable.

C. complex.

D. valuable.

Question 4 of 13：According to paragraph 5, in dry periods, 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.

Question 5 of 13：The word “progressively ” in the passage is closest in meaning to

A. openly.

B. impressively.

C. objectively.

D. increasingly.

Question 6 of 13：According to 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.

Question 7 of 13：The phrase “devoid of ” in the passage is closest in meaning to

A. consisting of.

B. hidden by.

C. except for.

D. lacking in.

Question 8 of 13：According to paragraph 9, the ground’s absorption of excess water is a factor in desertification because it 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.

Question 9 of 13：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.

Question 10 of 13：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 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 various countries are involved in the effort..

D. Desertification is extremely hard to reverse unless the population is reduced in the vast areas affected..

Question 11 of 13：It can be inferred from the passage 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 increase..

D. Desertification will soon occur in all areas of the world..

Question 12 of 13:Look at the four squares[■]that indicate where 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..

A.The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation.

B.The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil.

C.This is usually followed by the drying of the soil and accelerated erosion.

D.Firewood is the chief fuel used for cooking and heating in many countries.

Question 13 of 13：Directions: An introductory 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 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 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 with 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..

TPO2托福阅读Passage1解析

Question 1 of 13

正确答案：B

题目解析：

threaten: 威胁。A是限制;B是危及;C是阻止，避免;D是拒绝。和选项B呼应，所以正确答案是B。对应原文It has been estimated that an additional one-fourth of the Earth's land surface is threatened by this process.句子说大约1/4的土地收到这个过程的threaten。ACD代入后发现句子不通，只有B最合适。

Question 2 of 13

正确答案：B

题目解析：

用vegetation定位到第一句话： Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.这句话中明确说了，植被的减少导致土壤是去吸收大量水分的能力。这就对应了B选项。A在原文未提及，错;文中并没有说"spaces in the soil" increase了，所以C错;D选项和文中内容相反，所以错。

Question 3 of 13

正确答案：A

题目解析：

delicate: 易碎的，纤弱的。和选项A呼应。B是可预测的;C是复杂的;D是有价值的。对应原文he semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures.这句话中有并列关系，从and之后的limited可以推测出delicate应该是个负面的词，D首先被排除，D是正面词汇;BC是中性词，不选。只有A最合适。

Question 4 of 13

正确答案：A

题目解析：

用dry periods定位到最后一句： 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.这里强调了压力大于承受能力，pressure对应A选项中的stresses，A正确。选项B中的fertilit和C选项中的irrigatting crops没有被提及过, 所以B和C错。 选项D中的"attracting populations"也没有被提及到。

Question 5 of 13

正确答案：D

题目解析：

progressively: 渐进的，日益增多的。和选项D呼应。A是公开地;B是令人难忘地;C是客观地。对应原文The cultivation of crops has expanded into progressively drier regions as population densities have grown.这句话会所：当人口密度增加的时候，农作物的种植已经progressively扩展到更加干燥的地方了。

Question 6 of 13

正确答案：C

题目解析：

根据raising crops定位到最后一句： Since the raising of most crops necessitates the 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.这里说了，种植农作物需要事先移除自然植被，农作物的失败会让土地没有覆盖并且遭受到风和水的侵蚀。呼应C选项。

Question 7 of 13

正确答案：D

题目解析：

devoid of: 没有，缺乏。和选项D呼应。A是由…组成;B是被…隐藏;C是除了;D是缺乏。对应原文Since the raising of most crops necessitates the 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.原句有着明显的顺承关系，用and连接着，所以农作物失败留下土地devoid of植被覆盖，然后就遭受了侵蚀。这样的顺承关系可以退出，devoid of应该是否定的表达，没有了覆盖才会收到侵蚀。所以正确答案是D。

Question 8 of 13

正确答案：D

题目解析：

用excess water定位到第二句，但这句话并没有说出原因，往后看，后一句话出答案： If no drainage system exists, the water table rises, bringing dissolved salts to the surface.这句话明确说了，如果没有排水系统存在，地下水位会升高，把盐带到地表，和D选项呼应， 所以正确答案是D。ABC均未提及。

Question 9 of 13

正确答案：C

题目解析：

选项A的 "soil erosion" 在第二段第一句话有提及： Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion of the soil by wind and water.选项B, "global warning" 在第四段第二句所提及： Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years选项D, "raising of livestock" 在第七段倒数第二句所提及： The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil.选项C的irrigation在第9段提及，但是C说反，原文说overirrigation而不是insufficient，所以错，选： The final major human cause of desertification is soil salinization resulting from overirrigation.

Question 10 of 13

正确答案：A

题目解析：

这句话的主要逻辑是并列，并列的几个对象缺一不可：1)广大的土地;2)大量的人口受到影响;3)减缓或者倒转这个过程很困难。选项A的逻辑和原文呼应，并且并列的对象都包括在选项中，所以A正确;B选项的结果部分错误，原句是desertification的严峻形势，这里变成了减缓过程，而且原因部分没将3个部分都涵盖;C的solve这部分内容原句没有，纯属瞎编;D的unless结构和原文的逻辑不符。

Question 11 of 13

正确答案：C

题目解析：

本题较难，需联系首尾两段。文章开篇便指出沙漠已经(already)覆盖地球四分之一的面积，并且近年来沙漠化以惊人速度扩张(at an alarming pace)，使得又一四分之一的土地(an additional one-fourth of the Earth's land surface)面临威胁。文章结尾时总结到：土壤一旦被腐蚀，只有数百甚至千年后(only the passage of centuries or millennia)才能新生; though理解为"虽然"，作者意图说明虽然在那些土壤尚存的地方通过保护可能(may make it possible to reverse)可以制止恶化，但其实这句话还有言外之意，即那些已经腐蚀严重的地区前景就很不乐观了。综上，作者对沙漠化前景持悲观态度，认为沙化会继续扩张。因此选择C。

Question 12 of 13

正确答案：B

题目解析：

插入句中有明显的指代关系this economic reliance。所以到文中去找哪里提到了economic reliance。这几个选项中明显只有B前面依据的major economic activity和这个对应。

Question 13 of 13

正确答案：ACD

题目解析：

正确答案是 A, C, and D。A.C.D在文中都有提及，而B.E.F无提及。

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