资源描述：
《【素材】Module4文章SandstormsinBeijing(外研版).docx》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、SandstormsinBeijingAgeneraldefinitionofaseveresandstormisonethatitoccurssuddenlyandaffectslargeareascausinggreatlossestothenationaleconomyandthepeople.ThenumberofseveresandstormsinBeijinghasgrownrapidlysincethefoundingofthePeople'sRepublicofChina.Therewerefiveinthe1950s,eightinthe1960s,1
2、3inthe1970s,14inthe1980s,and20inthe1990s.SevereandwidespreadsandstormsmainlyoccurintheperiodfromMarchtoMay,especiallyinApril.Forinstance,adevastatingsandstormragedBeijingfromApril16to18,1998.Blowingfromwesttoeast,itevenstretchedtothelowerreachesoftheYangtzeRiver.Thisstormwasalmostunprece
3、dentedinhistory,andwhenitmetrainoverBeijing,'muddyrain'wasformed.Humanactivitiesplayanimportantroleintheformationofseveresandstorms,basicallythroughimproperuseofland,populationgrowthandtherapidspreadofurbanization.BeijingislocatedinthenorthernpartoftheNorthernPlainsofChina.Thewest(Taihan
4、gMountain),thenorth(JunduMountain)andtheeast(YanMountain)ofBeijingaremountainareas.Lotsofriversstreamoutfromtheseareas.SomeofthempassthroughtheterritoryofBeijing,forexampleYongding,ChaobaiandWenyuriverswhichusedtobebigriversinancienttimes,carryinglargequantitiesofwaterandhencecausingcons
5、iderableerosion,withmuchbedrockmovedalongtheircourse.Thespeedofwatersloweddownaftertheriversenteredintotheplain,andthebedloadssedimentedgradually.Beijingislocatedonthefan-shapedbed-rocksedimentsoriginatingfromtheTaihangMountain,JunduMountainandYanMountain.Originally,therewerelotsofflouri
6、shingvirginforests,whichhadtheobviousfunctionofpreventingsandywinds.However,duetowarsandtheneedsofconstructionfordevelopmentofBeijing,thesevirginforestswerecutdownandalmostexhausted.Onlysomereplantedtreeswereleftinscatteredmountainareas.Accordingtostatistics,thecoverrateofforestinBeijing
7、in1950swasonly1.33.5%.Strongwindshavebecomemorefrequent.Beijingareaisbelow50meters,buttheelevationofthenorthernmountainareaisabove1,000meters.Thedifferenceintopographyfacilitatesthewindenteringfrommountainareastoplainareas.Whenthewindpassesthroughtherivervalleys,duetothee
