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1、Erosion,New Words&Phrases,Erosion:The group of natural processes,including weathering,dissolution,abrasion(磨损）,corrosion（腐蚀）,and transportation,by which material is worn away（磨损）from the earths surface.,腐蚀，侵蚀：指使材料从地表磨损、消耗的一组自然过程，包括风化、溶解、磨蚀、浪蚀、腐蚀和搬运.,fluvial erosion 河流侵蚀geologic erosion 地质侵蚀loess ero
2、sion 黄土侵蚀rainfall erosion 降雨侵蚀river erosion 河流侵蚀sheet erosion 片状侵蚀stream bank erosion 河岸侵蚀wind erosion 风蚀,冲积层：河床、冲积平原或三角洲中的流水淤积所产生的沉积层.,Alluviuml(j)uvim:Sediment deposited by flowing water,as in a riverbed,flood plain,or delta.,alluvial：冲积的，淤积的.,Erode:To wear(something)away by or as if by abrasion;T
3、o cause to diminish（减小）,deteriorate（恶化）,or disappear as if by eating into or wearing away.,腐蚀；侵蚀：（象）被磨擦损耗掉;侵蚀掉，腐蚀掉：象磨蚀、侵蚀那样使减少、减弱或消失.,Silt:1）n.（名词）A sedimentary material consisting of very fine particles intermediate in size between sand and clay；泥沙，淤泥：由大小介于沙和泥之间的非常细小的微粒 构成的沉淀性物质 2）v.intr.（不及物动词）To
4、become filled with silt;被淤塞：使塞满泥沙 3)v.tr.（及物动词）To fill,cover,or obstruct with silt.使淤积：用沙充满、覆盖或阻碍,Siltation：冲积作用，淤积作用.,耕地：已耕作的土地耕种：开垦土地,Tillage:Land that has been tilled（耕种，耕耘）;Cultivation（耕种）of land.,黄土：一种风沉积而成的颗粒细小、含钙质的沙或泥土，呈浅黄色或黄褐色.,Loess:A buff to gray windblown（被风吹的）deposit of fine-grained,calc
5、areous（钙化的）silt or clay.,一、矿物质土粒石砾：1mm砂粒：1-0.05mm粉粒：0.05-0.002mm粘粒：0.002mm,土壤剖面结构,蒸散,TEXT,Erosion is an important natural process,rusulting in the redistribution of the products of geologic weathering,and is part of both soil formation and soil loss.The worlds landscapes have sculpted(雕刻）by erosion.
6、When the results are spectacular enough,we enshrine（铭记）them in national parks as we did with the Grand Canyon（峡谷）.Where erosion has worn down mountains and spread soil over the plains,or deposited rich alluvial silt in river bottomes,we galdly farm it.Erosion is a disaster only when it occurs in the
7、 wrong place at the wrong time.,Erosion is an important natural process,rusulting in the redistribution of the products of geologic weathering,and is part of both soil formation and soil loss.侵蚀是一个重要的自然过程，它导致了地质风化的产物的重新分配，是土壤形成和流失的部分原因。The worlds landscapes have sculpted(雕刻）by erosion.世界的地形和地貌就是由于侵蚀
8、的作用而形成的。When the results are spectacular enough,we enshrine（铭记）them in national parks as we did with the Grand Canyon.有时候，侵蚀的效果如此壮观，以至于我们用国家公园把它铭记下来，如美国的大峡谷。,Where erosion has worn down mountains and spread soil over the plains,or deposited rich alluvial silt in river bottomes,we galdly farm it.当侵蚀慢
9、慢磨损了山脉，并使平原覆盖了土壤，或者在河流底部形成富饶的底泥，人们会非常高兴有了可耕地。Erosion is a disaster only when it occurs in the wrong place at the wrong time.只有当侵蚀在错误的时间和错误的地方发生时，它才会成为一种灾难。,In some places,erosion occurs so rapidly that anyone can see it happen.Deep gullies（冲沟）are created where water scours away（冲刷）the soil,leaving f
10、ence posts and trees sitting on tall pedestals（地基）as the land erodes away around them.In most places,however,erosion is subtler（微妙的）.It is a creeping disaster that occurs in small increments（增量）.A thin layer of top soil is washed off fields year after year until eventually nothing is left but poor-q
11、uality sub-soil that requires more and more fertilizer and water to produce any crop at all.,In some places,erosion occurs so rapidly that anyone can see it happen.在某些地区，侵蚀的速度是如此之快，任何一个人都可以看见它的发生。Deep gullies are created where water scours away the soil,leaving fence posts and trees sitting on tall
12、pedestals as the land erodes away around them.当土壤受到水的冲刷，地表就形成了深深的沟壑，由于周围的土壤被冲走，只剩下树木和栅栏还树立在高高的地基上。In most places,however,erosion is subtler.然而，在大多数地区，侵蚀发生的更微弱些。,It is a creeping disaster that occurs in small increments.它（侵蚀）只是以很小的增量缓慢地发展成一场灾难。A thin layer of top soil is washed off fields year after
13、year until eventually nothing is left but poor-quality sub-soil that requires more and more fertilizer and water to produce any crop at all.表层土壤年复一年地被冲刷着，直到最后除了下层贫瘠的土壤什么也没有留下，为了产出庄稼需要越来越多的化肥和水。,The net effect,worldwide,of this general,wide spread top soil erosion is a reduction in crop production eq
14、uivalent to removing about 1%of world cropland each year.Many farmers are able to compensate for this loss by applying more fertilizer and by bringing new land into cultivation.Continuation of current erosion rates,however,could reduce agricultural production 25%in Central America and Africa and 20%
15、in South America by the year 2000.The total annual soil loss from croplands is thought to be 25 billion metric tons（公吨）.About twice that much soil is lost from rangelands(牧场）,forests,and urban construction sites each year.,The net effect,worldwide,of this general,wide spread top soil erosion is a re
16、duction in crop production equivalent to removing about 1%of world cropland each year.在世界范围内，这种大规模的表层土壤被侵蚀的结果是，每年农作物的减产相当于全世界耕地减少1%。Many farmers are able to conpensate for this loss by applying more fertilizer and by bringing new land into cultivation.很多农民通过施加更多化肥和开垦新的土地来补偿这种损失。,Continuation of curr
17、ent erosion rates,however,could reduce agricultural production 25%in Central America and Africa and 20%in South America by the year 2000.然而，这种侵蚀速度一直持续下去，到2000年，将会导致中美洲和非洲农业减产25%，南美洲农业减产20%。The total annual soil loss from croplands is thought to be 25 billion metric tons.About twice that much soil is
18、 lost from rangelands(牧场）,forests,and urban construction sites each year.据统计，每年耕地流失的土壤总数为250亿吨，大约是牧场、森林和城市建筑每年所损失的土壤的两倍。,In addtion to reduced land fertility,this erosion results in sediment-loading of rivers and lakes,of reservoirs,smothering(抑制，窒息）of wetlands and coral reefs,and clogging（阻塞）of wat
19、er intakes and waterpower turbines.It makes rivers unnavigable（）,increases the destructiveness and frequency of floods,and causes gullies that turns good lands into useless wastelands.,In addtion to reduced land fertility,this erosion results in sediment-loading of rivers and lakes,of reservoirs,smo
20、thering(抑制，窒息）of wetlands and coral reefs,and clogging（阻塞）of water intakes and waterpower turbines（涡轮发动机）.除了减少土壤肥力，侵蚀还导致了河流、湖泊和水库的淤积，使湿地和珊瑚礁窒息，堵塞了取水口和水力发动机。It makes rivers unnavigable（）,increases the destructiveness and frequency of floods,and causes gullies that turns good lands into useless wastel
21、ands.它使河流不能通航，增加了洪水发生的频率和破坏力，由于产生沟壑，是的优质土地变成荒地。,Wind and water are the main agents that move soil around.Thin,uniform layers of soil are peeled off(剥掉）the land surface in a process called sheet erosion.When little rivulets（小溪）of running water together and cut small channels in the soil,the process i
22、s called rill erosion.When rills enlarge to form bigger channels or ravines（沟壑）that too large to be removed by normal tillage operations,we call the process gully erosion.Stream bank erosion refers to the washing away of soil from the banks of established streams,creeks,or rivers,often as a result o
23、f removing trees and brush along stream banks and by cattle damage to the banks.,Wind and water are the main agents that move soil around.Thin,uniform layers of soil are peeled off(剥掉）the land surface in a process called sheet erosion.风和水也是搬运土壤的主要力量。一层薄薄的土壤从土地表面被剥离的过程称为片状侵蚀。When little rivulets（小溪）o
24、f running water together and cut small channels in the soil,the process is called rill erosion.当奔腾的小溪汇集在一起，在土壤中冲出小沟渠，这个过程称为细沟侵蚀。When rills enlarge to form bigger channels or ravines（沟壑）that too large to be removed by normal tillage operations,we call the process gully erosion.当细沟逐渐增大，形成大的河道或者溪谷，正常的耕
25、作已经不能把他们填平时，成这种侵蚀为溪谷侵蚀。,Stream bank erosion refers to the washing away of soil from the banks of established streams,creeks,or rivers,often as a result of removing trees and brush along stream banks and by cattle damage to the banks.河岸侵蚀指的是砍伐树木和河岸边的灌木丛或牲畜损害河岸而导致的已有的河流、小溪和大江岸边的土壤的流失。,Most soil erosio
26、n on agricultural land is sheet and rill erosion.Large amounts of soil can be transported by these mechanisms without being very noticeable.A farm field can lose 20 metric tons of soil per hectare(公顷）during winter and spring for runoff in rills so small that they are erased by the first spring culti
27、vation,that represent a loss of only a few millimeters of soil over the whole surface to the field,hardly apparent to any but most discerning（有辨识能力的）eye.But It doesnt take much mathematical skill to see that if you lose twice as fast as it is being replaced,eventually it will run out.,Most soil eros
28、ion on agricultural land is sheet and rill erosion.Large amounts of soil can be transported by these mechanisms without being very noticeable.大多数农业用地的土壤侵蚀是片状和沟状侵蚀。大量的土壤就是由于这种原因不为人知的进行转移。A farm field can lose 20 metric tons of soil per hectare(公顷）during winter and spring for runoff in rills so small
29、that they are erased（抹掉）by the first spring cultivation,that represent a loss of only a few millimeters of soil over the whole surface to the field,hardly apparent to any but most discerning（有辨识能力的）eye.在冬季和春季里农业用地每公顷损失土壤20吨。沟状流失很少以至于第一次春耕的侵蚀，仅仅是整个地区的表面土壤的几毫米的损失。除非用挑剔的眼光看，否则这个很不明显。,But It doesnt take
30、 much mathematical skill to see that if you lose twice as fast as it is being replaced,eventually it will run out.即使不运用数学技巧，也能看出如果土壤流失的速度是土壤更新速度的两倍，最后土壤将流失殆尽。Wind can equal or exceed water in erosive force,especially in a dry climate and on relatively flat land.When plant cover and surface litter ar
31、e removed from the land by agriculture or grazing,wind lifts loose soil particles and sweeps them away.风在侵蚀中的作用等同甚至超过水的作用，特别是在气候干燥、相对平坦的土地上。,Although data on soil condition and soil erosion in the world are not complete and difficult to access,it is evident that many places have very severe problems
32、.China,for example,has a large area of loess(windblown silt)deposits on the North China Plain that once was covered by forest and grassland.The forests were cut down and the grasslands were converted to cropland.This plateau is now scarred by gullies 30-40m deep,and the soil loss is thought to be at
33、 least 480 metric tons per hectare per year.This would be equivalent to 3cm of topsoil per year.,Although data on soil condition and soil erosion in the world are not complete and difficult to access,it is evident that many places have very severe problems.尽管全世界土壤条件和土壤侵蚀数据并不完全，并且很难得到，但很明显，在很多地区侵蚀是很严
34、重的问题。China,for example,has a large area of loess(windblown silt)deposits on the North China Plain that once was covered by forest and grassland.例如，中国的华北平原曾经被森林和草原覆盖，由于风的侵蚀，而变成了黄土沉积平原。,The forests were cut down and the grasslands were converted to cropland.森林被砍伐，草地被开垦成耕地。This plateau is now scarred b
35、y gullies 30-40m deep,and the soil loss is thought to be at least 480 metric tons per hectare per year.这片高地现在布满了30-40cm深的沟壑，每年每公顷土地至少有480吨土壤流失掉 This would be equivalent to 3cm of topsoil per year.这相当于每年流失了3cm厚的表层土壤。,5)Wind can equal or exceed water in erosive force,especially in a dry climate and on
36、 relatively flat land.When plant cover and surface litter are removed from the land by agriculture or grazing,wind lifts loose soil particles and sweeps them away.,6)Population pressures and preemption of good bottomlands for cash crop production have forced farmers to try to grow crops on steep,uns
37、table slopes.,7)As the river winds through northern China,much of this sediment settles out,raising the river bottom above the level of the surrounding countryside.Only by building dikes to contain the river have the Chinese been able to keep it in its course.,8)This high rate of erosion is both a c
38、ause and consequent of famine,poverty,and continued social unrest in that country.,Writing,1)What are the results of erosion?,2)How many kinds of erosions are mentioned in this text?What are they?,3)How many kinds of erosions forces are mentioned in this text?What are they?,4)Which river in the world has the highest concentration of sediment?,
