教学讲稿地形地貌学

《教学讲稿地形地貌学》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、CoastalProcessesandLandformsChapter13WavesMostaregeneratedbywindWavespropagateindirectionofprevailingwindSizeofwavesdependsonwindspeedwinddurationfetchWatermovementduetowavesForwavesindeepwater:Aswavespass,waterexperiencescircular(orbital)motion--nonetflowofwaterSizeofo

2、rbitsdecreaseswithdepthWavebase--depthbelowwhichoscillatorymotionceasesWavebaseexistsatdepthequaltoone-halfwavelengthofsurfacewavesDeepwaterwavesH-waveheightL-wavelengthWavesinshallowwaterWherewaterdepthislessthanwavebase,wavesexperiencedragfromseabedThisfrictioncausesw

3、avestoslowandsteepen(H/Lincreases)watermotionbeneathwavesbecomesellipticalWavesinshallowwaterWavesinshallowwaterWaveseventuallybreakwhendepthgetsveryshallow.Zoneofbreakingwavesiscalledthesurfzone.Swashzoneiswherewaterrushesupandwashesbackdownbeachface.SurfzoneSwashfaceT

4、sunamisTsunamis-generatedbyvolcaniceruptions,earthquakesorlandslides.Generatelarge,longperiodwavesthattravelquicklytoshore,steepeningastheyentershallowwater.Seiche--commononlakesSeicheresultsfromwindsetupordifferencesinbarometricpressurethatcauseelevationofwatersurfacei

5、nonearea.Resultsinperiodicfluctuationsinwaterlevelsaswates“sloshes”backandforth.EntrainmentthresholdforwavetransportTidesGeneratedbygravitationalpullofmoonandsunonseasurfaceInmostplaces,tiderises&fallstwicedaily(semi-diurnaltides)TidesHigher“springtides”occurwhenmoonand

6、sunarealigned(newandfullmoon);lower“neaptides”occurwhenmoonandsunareat90oEffectsoftidesInfluencesthelandwardextentofwaveactionCreatestidalcurrents,especiallyinestuaries,bays,lagoons,andinlets.Currents(otherthantidalcurrents)Longshorecurrents--shore-parallelflow;maybepar

7、tofcirculationcellthatincludeslongshoreandripcurrents,ormaybeprimarilywind-driven.Ripcurrents--narrow,offshoreflowofwaterseawardofsurfzoneFromKomar,1976RipcurrrentsCellsdevelopduetoalongshorevariationsinwaveheightWherewavesarehigher,setupisgreater(higherwatersurfaceelev

8、ations).Driveswaterfromtheseareastowheresetupisataminimum(locationofrips)LongshoreCurrents--originShore-parall