关闭图标
log图标

toefl.viplgw.cn

  • 使用手机注册
  • 使用邮箱注册
  • 手机号不能为空!

    验证码不能为空!

    用户名不能为空!

    密码不能为空!

  • 邮箱不能为空!

    验证码不能为空!

    用户名不能为空!

    密码不能为空!

已有账号? 登录到雷哥托福
关闭图标
log图标
  • 使用手机找回密码
  • 使用邮箱找回密码
  • 手机号不能为空!

    验证码不能为空!

    密码不能为空!

  • 邮箱不能为空!

    验证码不能为空!

    密码不能为空!

又想起来了
加入生词本

listen

英['lɪs(ə)n] 美['lɪsn]
vi. 听,倾听;听从,听信
n. 听,倾听

已添加
×

我要举报草莓小菇凉评论

用户头像
草莓小菇凉:说的非常好,十分有道理,棒棒棒!

06-08 15:44:55

请选择举报类型:

举报电话:400-0181-6180    举报QQ:2095453331
×
logo图标
分享到雷哥托福

分享成功图标分享成功

邀请名师点评成功,管理员正在安排老师进行点评。

继续做题 返回首页
支付雷豆失败图标 雷豆余额不足 购买雷豆 返回
报告题目错误
请选择错误类型:
请描述一下这个错误:

取消

TPO-02- 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.

已经占据地球表面约四分之一的沙漠近几十年来以惊人的速度增长。沙漠化的条件扩大到以前不存在的地区称为荒漠化。据估计,地球另外四分之一的陆地表面受到这一过程的威胁。

 

荒漠化主要是通过失去稳定的天然植被,随后加速风蚀和水侵蚀土壤来实现的。在某些情况下,松散的土壤被完全吹走,留下石质的表面。在其他情况下,更细的颗粒可能被去除,而沙粒大小积累形成移动的山丘或沙脊。

 

即使在保持土壤覆盖的地区,植被的减少通常也会导致土壤吸收大量水分的能力丧失。雨滴对松散土壤的影响倾向于将细小的粘土颗粒转移到最微小的土壤空间中,将它们密封起来,并产生一个表面,使水分很少渗透。吸水率大大降低;因此径流增加,导致加速侵蚀率。由于其吸收水分的能力降低而导致的土壤逐渐干燥导致植被的进一步损失,从而形成逐渐恶化的表面恶化周期。

 

在一些地区,沙漠地区的增加主要是由于气候条件趋于干旱的结果。过去几千年来,持续不断的全球变暖使一些地区的干旱程度加剧。如果由空气污染造成的全球变暖严重增加,这个过程可能会在随后的几十年里加速。

 

然而,毫无疑问,大部分地区的荒漠化主要是由人类活动而非自然过程造成的。与沙漠接壤的半干旱土地处于微妙的生态平衡状态,受到适应环境压力增加的潜力限制。越来越多的人口受到越来越大的压力,为他们提供食物和燃料。在潮湿时期,这片土地可能会对这些压力做出反应。在沙漠边缘常见的干旱时期,土地的压力往往远远大于其减少的能力,导致沙漠化。

 

已经确定四个具体的活动是荒漠化进程的主要贡献者:过度耕作,过度放牧,采柴和过度灌溉。随着人口密度的增长,农作物的种植已经扩大到日益干燥的地区。这些地区特别可能有严重干旱的时期,所以作物歉收是常见的。由于大部分作物的种植需要事先清除自然植被,因此作物歉收会留下大片无植物覆盖的土地,易受风蚀和水蚀的侵蚀。

 

饲养牲畜是半干旱地区的主要经济活动,在这些地区,草类一般是自然植被的主要类型。在一个地区放牧过多牲畜的后果是减少植被覆盖和践踏和粉碎土壤。这通常是随后的土壤干燥和加速侵蚀。

 

柴火是许多国家用于烹饪和取暖的主要燃料。人口不断膨胀的压力加大,导致木本植物被清除,许多城镇被大面积的树木和灌木所包围。由于这种宝贵的土壤调理剂和植物营养物质的来源不再被返回到土地,越来越多地使用干的动物废物作为替代燃料也伤害了土壤。

 

沙漠化的最终主要原因是过度灌溉造成的土壤盐碱化。灌溉过量的水汇入地下水位。如果没有排水系统,地下水位上升,将溶解的盐带到地表。水分蒸发,盐分留下,形成白色地壳层,阻止空气和水分到达下面的土壤。

 

沙漠化的严重性来自广大地区和受灾人口的巨大,以及扭转甚至减缓这一进程的巨大困难。一旦土壤被侵蚀去除,只有几百年或几千年才能形成新的土壤。然而,在仍然存在大量土壤的地区,严格执行的土地保护和覆盖作物种植计划可以扭转目前地表恶化的局面。

中文翻译

The word threatened in the passage is closest in meaning to

  • It has been estimated that an additional one-fourth of the Earth's land surface is threatened by this process. A Restricted B Endangered C Prevented D Rejected threatened
正确答案: B

网友解析

  • 用户头像

    恩恩耶  发表于 2018-07-24 15:08:22

    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。

  • 用户头像

    joannazz  发表于 2017-12-06 15:09:41

    threaten 威胁、恐吓,最接近B endanger危及

  • 用户头像

    joannazz  发表于 2017-12-06 15:07:22

    词汇题: threaten 威胁、恐吓,最接近B endanger危及

题目讨论

  • 用户头像

    恩恩耶  发表于 07-24 15:08:36

    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。

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:55

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:55

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:55

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:55

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:54

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:54

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:54

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:53

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 用户头像

    joannazz  发表于 12-06 15:16:51

    事实信息题: 根据题干loss of natural vegetation定位到the reduction of vegetation typically results in the loss of the soil's ability to absorb substantial quantities of water.本句指出植被减少将导致土壤吸收水分能力下降,即B选项reduced water absorption 

    • (0)
    • |
    • 回复(0)
    • |
    • 举报
  • 1

雷哥托福微信

  • 微信公众号:toeflgo

    二维码
  • 小托君:Toefl12345

    二维码
查看详情图片

您已提交评论成功

确定