环境科学专业英语3.ppt

Erosion,Unit Three,Jinyan Yang,10-11-2010,New Words & Phrases,Erosion: The group of natural processes, including weathering, dissolution, abrasion, corrosion, and transportation, by which material is worn away 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 erosion 黄土侵蚀 rainfall erosion 降雨侵蚀 rill erosion 细沟侵蚀 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、洪水淹没的平原或三角洲中的流水淤积所产生的沉积层.,Alluvium: 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; To cause to diminish, deteriorate, 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）r.（不及物动词）To 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; Cultivation 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 deposit of fine-grained, calcareous silt or clay.,Translation,1) A thin layer of top soil is washed off fields year after 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.,2) The net effect, worldwide, of this general, wide spread top soil erosion is a reduction in crop production equivalent to removing about 1% of world cropland each year.,3) The total annual soil loss from croplands is thought to be 25 billion metric tons. About twice that much soil is lost from rangelands, forests, and urban construction sites each year.,4) 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.,5) 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 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, unstable 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 cause 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