GMAT网络课堂阅读笔记-王昆嵩主讲[4]
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(单词翻译:双击或拖选)

In choosing a method for determining climatic condi-
  tions that existed in the past, paleoclimatologists invoke1
  four principal criteria2. First, the material-rocks, lakes,
  vegetation, etc.-on which the method relies must be
(5) widespread enough to provide plenty of information,
  since analysis of material that is rarely encountered will
  not permit correlation3 with other regions or with other
  periods of geological history. Second, in the process of
  formation, the material must have received an environ-
(10) mental signal that reflects a change in climate and that
  can be deciphered by modern physical or chemical
  means. Third, at least some of the material must have
  retained the signal unaffected by subsequent changes in
  the environment. Fourth, it must be possible to deter-
(15) mine the time at which the inferred climatic conditions
  held. This last criterion is more easily met in dating
  marine4 sediments5, because dating of only a small
  number of layers in a marine sequence allows the age of
  other layers to be estimated fairly reliably by extrapola-
(20) tion and interpolation. By contrast, because sedimenta-
  tion is much less continuous in continental6 regions, esti-
  mating the age of a continental bed from the known
  ages of beds above and below is more risky7.
  One very old method used in the investigation8 of past
(25) climatic conditions involves the measurement of water
  levels in ancient lakes. In temperate9 regions, there are
  enough lakes for correlations10 between them to give us a
  reliable picture. In arid11 and semiarid12 regions, on the
  other hand, the small number of lakes and the great
(30) distances between them reduce the possibilities for corre-
  lation. Moreover, since lake levels are controlled by rates
  of evaporation13 as well as by precipitation, the interpreta-
  tion of such levels is ambiguous. For instance, the fact
  that lake levels in the semiarid southwestern United
(35) States appear to have been higher during the last ice age
  than they are now was at one time attributed to
  increased precipitation. On the basis of snow-line eleva-
  tions, however, it has been concluded that the climate
  then was not necessarily wetter than it is now, but rather
(40) that both summers and winters were cooler, resulting in
  reduced evaporation.
  Another problematic method is to reconstruct former
  climates on the basis of pollen14 profiles. The type of vege-
  tation in a specific region is determined15 by identifying
(45) and counting the various pollen grains found there.
  Although the relationship between vegetation and
  climate is not as direct as the relationship between
  climate and lake levels, the method often works well in
  the temperate zones. In arid and semiarid regions in
4. Which of the following would be the most likely topic for a paragraph that logically continues the passage?
(A) The kinds of plants normally found in arid regions
(B) The effect of variation in lake levels on pollen distribution
(C) The material best suited to preserving signals of climatic changes
(D) Other criteria invoked16 by paleoclimatologists when choosing a method to determine past climatic
conditions
(E) A third method for investigating past climatic conditions

 

(50) which there is not much vegetation, however, small
  changes in one or a few plant types can change the
  picture dramatically, making accurate correlations
  between neighboring areas difficult to obtain.

1. Which of the following statements about the difference between marine and continental sedimentation17 is supported by information in the passage?
(A) Data provided by dating marine sedimentation is more consistent with researchers' findings in other disciplines than is data provided by dating continental sedimentation.
(B) It is easier to estimate the age of a layer in a sequence of continental sedimentation than it is to estimate the age of a layer in a sequence of marine sedimentation.
(C) Marine sedimentation is much less widespread than continental sedimentation.
(D) Researchers are more often forced to rely on extrapolation when dating a layer of marine sedimentation than when dating a layer of continental sedimentation.
(E) Marine sedimentation is much more continuous than is continental sedimentation.

2. Which of the following statements best describes the organization of the passage as a whole?
(A) The author describes a method for determining past climatic conditions and then offers specific examples of situations in which it has been used.
(B) The author discusses the method of dating marine and continental sequences and then explains how dating is more difficult with lake levels than with pollen profiles.
(C) The author describes the common requirements of methods for determining past climatic conditions and then discusses examples of such methods.
(D) The author describes various ways of choosing a material for determining past climatic conditions and then discusses how two such methods have yielded contradictory18 data.
(E) The author describes how methods for determining past climatic conditions were first developed and then describes two of the earliest known methods.
3. It can be inferred from the passage that paleoclimatologists have concluded which of the following on the basis of their study of snow-line elevations19 in the southwestern United States?
(A) There is usually more precipitation during an ice age because of increased amounts of evaporation.
(B) There was less precipitation during the last ice age than there is today.
(C) Lake levels in the semiarid southwestern United States were lower during the last ice age than they are today.
(D) During the last ice age, cooler weather led to lower lake levels than paleoclimatologists had previously20 assumed.
(E) The high lake levels during the last ice age may have been a result of less evaporation rather than more precipitation

5. The author discusses lake levels in the southwestern United States in order to
(A) illustrate21 the mechanics of the relationship between lake level, evaporation, and precipitation
(B) provide an example of the uncertainty22 involved in interpreting lake levels
(C) prove that there are not enough ancient lakes with which to make accurate correlations
(D) explain the effects of increased rates of evaporation on levels of precipitation
(E) suggest that snow-line elevations are invariably more accurate than lake levels in determining rates of precipitation at various points in the past

6. It can be inferred from the passage that an environmental signal found in geological material would not be useful to paleoclimatologists if it
(A) had to be interpreted by modern chemical means
(B) reflected a change in climate rather than a long- term climatic condition
(C) was incorporated into a material as the material was forming
(D) also reflected subsequent environmental changes
(E) was contained in a continental rather than a marine sequence

 

Keys: ECEEB DDA



点击收听单词发音收听单词发音  

1 invoke G4sxB     
v.求助于(神、法律);恳求,乞求
参考例句:
  • Let us invoke the blessings of peace.让我们祈求和平之福。
  • I hope I'll never have to invoke this clause and lodge a claim with you.我希望我永远不会使用这个条款向你们索赔。
2 criteria vafyC     
n.标准
参考例句:
  • The main criterion is value for money.主要的标准是钱要用得划算。
  • There are strict criteria for inclusion in the competition.参赛的标准很严格。
3 correlation Rogzg     
n.相互关系,相关,关连
参考例句:
  • The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。
  • A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。
4 marine 77Izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • When the war broke out,he volunteered for the Marine Corps.战争爆发时,他自愿参加了海军陆战队。
5 sediments 8b3acb612b624abdf2c2881bc6928565     
沉淀物( sediment的名词复数 ); 沉积物
参考例句:
  • When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后,体积的70-80%是水。
  • Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。
6 continental Zazyk     
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。
7 risky IXVxe     
adj.有风险的,冒险的
参考例句:
  • It may be risky but we will chance it anyhow.这可能有危险,但我们无论如何要冒一冒险。
  • He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。
8 investigation MRKzq     
n.调查,调查研究
参考例句:
  • In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
  • He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。
9 temperate tIhzd     
adj.温和的,温带的,自我克制的,不过分的
参考例句:
  • Asia extends across the frigid,temperate and tropical zones.亚洲地跨寒、温、热三带。
  • Great Britain has a temperate climate.英国气候温和。
10 correlations 4a9b6fe1ddc2671881c9aa3d6cc07e8e     
相互的关系( correlation的名词复数 )
参考例句:
  • One would expect strong and positive correlations between both complexes. 人们往往以为这两个综合体之间有紧密的正相关。
  • The correlations are of unequal value. 这些对应联系的价值并不相同。
11 arid JejyB     
adj.干旱的;(土地)贫瘠的
参考例句:
  • These trees will shield off arid winds and protect the fields.这些树能挡住旱风,保护农田。
  • There are serious problems of land degradation in some arid zones.在一些干旱地带存在严重的土地退化问题。
12 semiarid oiozuX     
adj.雨量非常少的,半干旱的
参考例句:
  • The region is semiarid to arid in overall climate.这个地区总体上是半干旱至干旱气候。
  • In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge,usually because of a lack of moisture.在很多半干旱地带也有下层的树带界限,在这种环境中,由于缺乏水分,森林下缘逐渐变成干草原或者是沙漠。
13 evaporation Pnoxc     
n.蒸发,消失
参考例句:
  • Be careful not to lose too much liquid by evaporation.小心不要因蒸发失去太多水分。
  • Our bodies can sweat,thereby losing heat by evaporation.我们的身体能出汗,由此可以蒸发散热。
14 pollen h1Uzz     
n.[植]花粉
参考例句:
  • Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
  • He developed an allergy to pollen.他对花粉过敏。
15 determined duszmP     
adj.坚定的;有决心的
参考例句:
  • I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
  • He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
16 invoked fabb19b279de1e206fa6d493923723ba     
v.援引( invoke的过去式和过去分词 );行使(权利等);祈求救助;恳求
参考例句:
  • It is unlikely that libel laws will be invoked. 不大可能诉诸诽谤法。
  • She had invoked the law in her own defence. 她援引法律为自己辩护。 来自《简明英汉词典》
17 sedimentation msEyJ     
n.沉淀,沉积
参考例句:
  • Sedimentation, the damage of a breach are problems, too. 而且沉积和决口的问题,也是存在的。 来自英语晨读30分(高二)
  • Sedimentation and denudation play a role in exceptional cases. 沉积和剥蚀作用的影响只在特殊情况下起作用。
18 contradictory VpazV     
adj.反驳的,反对的,抗辩的;n.正反对,矛盾对立
参考例句:
  • The argument is internally contradictory.论据本身自相矛盾。
  • What he said was self-contradictory.他讲话前后不符。
19 elevations cb4bbe1b6e824c996fd92d711884a9f2     
(水平或数量)提高( elevation的名词复数 ); 高地; 海拔; 提升
参考例句:
  • Weight of the crust changes as elevations are eroded and materials are deposited elsewhere. 当高地受到侵蚀,物质沉积到别的地方时,地壳的重量就改变。
  • All deck elevations are on the top of structural beams. 所有甲板标高线均指结构梁顶线。
20 previously bkzzzC     
adv.以前,先前(地)
参考例句:
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
21 illustrate IaRxw     
v.举例说明,阐明;图解,加插图
参考例句:
  • The company's bank statements illustrate its success.这家公司的银行报表说明了它的成功。
  • This diagram will illustrate what I mean.这个图表可说明我的意思。
22 uncertainty NlFwK     
n.易变,靠不住,不确知,不确定的事物
参考例句:
  • Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
  • After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后,压力开始产生影响了。
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