Glacial Deposits - Geology - Cliffs Notes

The sediments deposited by glacial meltwater are called outwash. Since they have been transported by running water, the outwash deposits are braided, sorted, ... MyPreferences MyReadingList Geology ! 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Featuresleftbyvalleyglaciersandicesheets.MorainesleftbyvalleyglaciersareshowninFigure1,andfeaturesleftbyarecedingicesheetareshowninFigure2.Morainesaredepositsoftillthatareleftbehindwhenaglacierrecedesorthatarecarriedontopofalpineglaciers.Lateralmorainesconsistofrockdebrisandsedimentthathaveworkedloosefromthewallsbesideavalleyglacierandhavebuiltupinridgesalongthesidesoftheglacier.Medialmorainesarelongridgesoftillthatresultwhenlateralmorainesjoinastwotributaryglaciersmergetoformasingleglacier.Asmoretributaryglaciersjointhemainbodyofice,aseriesofroughlyparallelmedialmorainesdeveloponthesurfaceofmainglacier. Figure1    Moraines Figure2 LandformsProducedAfterIceRecession Anextensivepileoftillcalledanendmorainecanbuildupatthefrontoftheglacierandistypicallycrescentshaped.Twokindsofendmorainesarerecognized:terminalandrecessionalmoraines.Aterminalmoraineistheridgeoftillthatmarksthefarthestadvanceoftheglacierbeforeitstartedtorecede.Arecessionalmoraineisonethatdevelopsatthefrontoftherecedingglacier;aseriesofrecessionalmorainesmarkthepathofaretreatingglacier. Athin,widespreadlayeroftilldepositedacrossthesurfaceasanicesheetmeltsiscalledagroundmoraine.Groundmorainematerialcansometimesbereshapedbysubsequentglaciersintostreamlinedhillscalleddrumlins,long,narrow,roundedridgesoftillwhoselongaxesparallelthedirectiontheglaciertraveled. Asaglaciermelts,tillisreleasedfromtheiceintotheflowingwater.Thesedimentsdepositedbyglacialmeltwaterarecalledoutwash.Sincetheyhavebeentransportedbyrunningwater,theoutwashdepositsarebraided,sorted,andlayered.Thebroadfrontofoutwashassociatedwithanicesheetiscalledanoutwashplain;ifitisfromanalpineglacieritiscalledavalleytrain.Kamesaresteep‐sidedmoundsofstratifiedtillthatweredepositedbymeltwaterindepressionsoropeningsintheiceorasshort‐liveddeltasorfansatthemouthsofmeltwaterstreams.Therapidbuild‐upofsedimentscanburyisolatedblocksofice.Whentheicemelts,theresultantdepressioniscalledakettle.Kettlelakes,commonintheupperMidwestoftheUnitedStates,arebodiesofwaterthatoccupykettles. Eskersarelong,windingridgesofoutwashthatweredepositedinstreamsflowingthroughicecavesandtunnelsatthebaseoftheglacier.Generallywellsortedandcross‐bedded,eskersandsandgravelseventuallychokeoffthewaterway. Thegreatvolumeofmeltwateroftenresultsintheformationofglaciallakesbetweentheendmorainesandtheretreatingglacierfront.Thesedimentsthatformatthebottomofthelakeconsistoffine‐grainedsiltandclaythathaveanalternatinglight‐darklayering.Avarveconsistsofonelight‐coloredbedandonedark‐coloredbedthatrepresentasingleyear'sdeposition.Thelight‐coloredlayerismostlysiltthatwasdepositedrapidlyduringthesummermonths;thedarklayerconsistsofclayandorganicmaterialthatformedduringthewinter.Theageofaglaciallakecanbedeterminedfromthenumberofvarvesthathaveformedonthelakebottom. Previous GlacialLandforms Next GlaciersinthePast TheEarth'sExterior GeologicTime TheEarthToday HistoryofPhysicalGeology TheEarth'sOrigin TheEarth'sStructure MineralProperties TheRockCycle ChemicalComposition MineralsandRocks ExtrusiveRockTypes RockTextures IntrusiveRockTypes IntrusiveStructures HowDifferentMagmasForm IgneousRocksandPlateTectonics MagmaticDifferentiation VolcanoesandLavas ClasticSedimentaryRocks ChemicalSedimentaryRocks OrganicSedimentaryRocks SedimentaryFeatures SedimentaryEnvironments HowSedimentaryRocksForm FactorsControllingMetamorphism TypesofMetamorphism MetamorphicRockTypes HydrothermalRocks MetamorphismandPlateTectonics MetamorphismDefined InterpretingStructures MappingintheField Folding Fracturing Unconformities GeologicStructuresDefined TectonicForces ProcessesofMechanicalWeathering ProcessesofChemicalWeathering Soil Weathering PreventionofMassWasting IntroductiontoMassWasting Mass‐WastingControls TypesofMassWasting StreamDynamics StreamErosion SedimentLoad StreamDeposition StreamValleys RegionalErosion TypesofWaterFlow HowGlaciersDevelop GlacierMovement GlacialErosion GlacialLandforms GlacialDeposits GlaciersinthePast IntroductiontoGlaciation TypesofGlaciers NorthAmericanGlaciation Permeability TheWaterTable StreamsandSprings EffectsofGroundwaterFlow GroundwaterPollution GeothermalEnergy GroundwaterandInfiltration Porosity Beaches ShorelineFeatures Tides Waves DesertFeatures TheEffectsofWind DistributionandCausesofDeserts MonitoringEarthquakes EffectsofEarthquakes EarthquakesandPlateTectonics ControlandPrediction HowEarthquakesForm SeismicWaves TheCrust TheMantle IsostaticEquilibrium TheCore MagneticFields GeophysicsDefined Gravity SeismicWaves:MethodsofDetection TheStructureoftheEarth GeothermalGradients ContinentalMargins OceanFloorSediments ActiveContinentalMargins PassiveContinentalMargins Reefs InvestigativeTechnologies MidoceanicRidges OceanicCrust HowPlatesMove TypesofPlateBoundaries WhyPlatesMove MantlePlumes Pangaea EarlyEvidenceforPlateTectonics PaleomagneticEvidence SeaFloorEvidence FeaturesofMountainBelts TypesofMountains HowMountainsForm HowContinentsForm IntroductiontoMountains GeologicCorrelations AbsoluteAge ASummaryofEarth'sHistory GeologicTimeDefined RelativeTime MetallicDeposits EnergyResources NonmetallicResources RecyclingandConservation ResourcesandReserves Earth'sMoon Mars JupiterandSaturn IntroductiontotheSolarSystem Mercury Venus × BacktoTop AdamBede hasbeenaddedtoyour ReadingList! 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