Geomorphology of the Pacific Northwest - Ecoshare · PDF fileGeomorphology of the Pacific...

GeomorphologyofthePacificNorthwestLegendandGlossaryDefinitionsandDescriptionsofTermsUsedintheMappingofLandforms,LandformGroups,andLandformAssociationsinRegionSix,ForestService

JayS.NollerOregonStateUniversityCorvallis,OregonSarahJ.HashForestServiceBend,OregonKarenBennettForestServicePortland,OregonDecember2013ver.0.7DRAFT

2

NotetotheReaderThisprovisional,drafttextpresentsandbrieflydescribesthetermsusedinthepreparationofamapoflandformgroupscoveringallforestswithinRegionSixoftheUSForestService.FormaldefinitionofmapunitsispendingcompletionofthismapandreviewthereofbyalloftheforestsinRegionSix.MapunitnamesappendedtoGISshapefilesareconcatenationsoftermsdefinedhereinandaremeanttobeobjectivedescriptorsofthelandscapewithineachmapunitboundary.Thesemapunitnameshaveyettoundergoafinalvettingandcullingtoreducecomplexity,redundancyorobfuscationunintentionallyresultingfrommapcreationactivities.Anyomissionsorerrorsinthisdraftdocumentaretheresponsibilityofitsauthors.Rev.06on05December2013byJayNoller

GeomorphologyofthePacificNorthwest–MapLegendTerm Description

3

AncientVolcanoes Landformgroupssuggestiveofadeeplyerodedvolcano.Typicallyacentralhypabyssalorshallowplutonicrocksarepresentincentral(core)areaoftherelictvolcano.

Apron Footslopetotoeslopepositionsofvolcanoestomountainranges.Synonymouswithbajadainanalluvialcontext.

Ballena Distinctivelyround-topped,paralleltosub-parallelridgelinesandinterveningvalleysthathaveanoverallfan-shapedordistributarydrainagepattern.Theridge'sbroadlyroundedshouldersmeetfromeithersidetoformanarrowcrestandmergesmoothlywiththeconcavebackslopes.LocallyappliedtoremnantsoffanalluviumoftheGreatBasin(cf.Peterson,1981)[FSGeomorph],butusedasalandformsensostrictuwithoutreferencetounderlyinglithology.

Canyon Long,deep,relativelynarrowsteep-sidedvalleyconfinedbetweenloftyandprecipitouswallsinaplateauormountainousarea,oftenwithastreamatthebottom;similarto,butlargerthan,agorge.Itischaracteristicofaridorsemiaridareaswherestreamdowncuttinggreatlyexceedsweathering(BJ1995,FSGeomorph)

Canyonlands Drainagecharacterizedbyaseriesoflong,deep,relativelysteep-sidedvalleyswhichgenerallyoccurwithinplateausormountainouscountryinaridorsemiaridclimates(FSGeomorph)

CirqueBasin Deep,steep-walledhalf-bowl-likerecessorhollow,variouslydescribedashorseshoe-orcrescent-shapedorsemicircularinplan,situatedhighonthesideofamountainandcommonlyattheheadofaglacialvalley,andproducedbytheerosiveactivityofamountainglacier.Itoftencontainsasmallroundlake,anditmayormaynotbeoccupiedbyiceorsnow.

CraterWall Acraterisabasinlike,rimmedstructurethatisusuallyatthesummitofavolcaniccone.Itmaybeformedbycollapse,byanexplosiveeruption,orbythegradualaccumulationofpyroclasticmaterialinasurroundingrim.

Cuesta ahillorridgewithagentleslopeononesideandasteepslopeontheother;specificallyanasymmetricridgewithoneface(dipslope)longandgentleandconformingwiththedipoftheresistantbedorbedsthatformit,andtheoppositeface(scarpslope)steeporevencliff-likeandformedbytheoutcropoftheresistantrocks,theformationoftheridgebeingcontrolledbythedifferentialerosionofthegentlyinclinedstrata(BJ1995,FSGeomorph)

Delta low,nearlyflat,alluvialtractoflandatournearthemouthofariver,commonlyformingatriangularorfan-shapedplainofconsiderablearea,crossedbymanydistributariesofthemainriver,perhapsextendingbeyondthegeneraltrendofthecoast,andresultingfromtheaccumulationofsedimentsuppliedbytheriverinsuchquantitiesthatitisnotremovedbytides,waves,andcurrents.Mostdeltasarepartysubaerialandpartlybelowwater(BJ1995,FSGeomorph)


4

Deposit Earthmaterialofanytype,eitherconsolidatedorunconsolidated,thathasaccumulatedbyvariousmasswastingprocesses(BJ1995,FSGeomorph)

Drift Anall-inclusivetermforanykindofrockmaterialtransportedanddepositedbytheiceormeltwaterofglaciers(Tuttle)

Dune Alowmound,ridge,bank,orhillofloose,windblowngranularmaterial(generallysand,sometimesvolcanicash),eitherbareorcoveredwithvegetation,capableofmovementfromplacetoplacebutalwaysretainingitscharacteristicshape.(BJ1995,FSGeomorph)

DuneField Anexpansecoveredbydunes(BJ1995,FSGeomorph)Escarpment Along,moreorlesscontinuousclifforrelativelysteepslopefacing

inonegeneraldirection,breakingthecontinuityofthelandbyseparatingtwolevelorgentlyslopingsurfaces,andproducedbyerosionorbyfaulting.Thetermisoftenusedsynonymouslywithscarp,althoughescarpmentismoreoftenappliedtoacliffformedbydifferentialerosion(BJ1995,FSGeomorph)

Estuary Theseawardendorthewidenedfunnel-shapedtidalmouthofarivervalleywherefreshwatercomesintocontactwithseawaterandwheretidaleffectsareevident;e.g.atidalriver,orapartiallyenclosedcoastalbodyofwaterwherethetidemeetsthecurrentofastream(BJ1995,FSGeomorph)

ExtendedTerrain Surfacemorphologypreservinglandformsincludinghorsts,grabens,sags,shears,escarpments,divertedstreamsandotherextensionaltectoniclandforms.

Fan agentlysloping,fan-shapedmassofdetritusformingasectionofalow-angleconecommonlyataplacewherethereisanoticeabledecreaseingradient;specificallyanalluvialfan

Flank(e.g.volcanicflank) Lowerthirdofasideslope,belowaslopebreaktransitionfromsteeperslopetomoregradualslope

Flows SeeLavaFlowsFoothills Aregionofrelativelylow,roundedhillsatthebaseoforfringinga

mountainrange(BJ1995,FSGeomorph)Gorge Anarrowdeepvalleywithnearlyverticalrockywalls,enclosedby

mountains,smallerthanacanyon,andmoresteep-sidedthanaravine;especiallyarestrictedsteep-walledpartofacanyon(BJ1995,FSGeomorph)

HangingValley Aglacialvalleywhosemouthisatarelativelyhighlevelonthesteepsideofalargerglacialvalley.Thelargervalleywaserodedbyatrunkglacierandthesmalleronebyatributaryglacier,andthediscordanceofleveloftheirfloors,aswellastheirdifferenceinsize,isduetothegreatererosivepowerofthetrunkglacier(BJ1995,FSGeomorph)

Highlands Generaltermforarelativelylargeareaofelevatedormountainouslandstandingprominentlyaboveadjacentlowareas;amountainousregion.Thetermisoftenusedinthepluralina


5

propername.BJ1995,FSGeomorph)

Hills **SeeMeybeckdefinitionbelowHillslopes Slopesofhills.IceCap Amassoficeandsnowthatpermanentlycoversalargeareaof

land,i.e.amountainrange(relictfeature)(smallerthananicesheet)

IceCapBorderlands AreasneighboringtheIceCapMargin,butnotdirectlyimpactedbytheIceCapitself;internallandformsmayreflectthepresenceoftheIceCap.

IceCapHighlands AreasoncecoveredbyanIceCapandthatnowtopographicallystandinhigherreliefthatsurroundingdeglaciatedarea.

IceCapMargin Sculptedbyiceanddepositionofdriftandloessalongthemaximumextentboundaryofamountainicecap.

IceCapMoraine Glacialtilldepositedinaridge-likelandform(moraine)paralleltotheicecapmargin.

IceCapPlain Sculptedbyiceandinwashdepositionwithinthe'footprint'ofamountainicecap.

IceCapSlopesandValleys Landformssculptedbyicewithinthe'footprint'ofamountainicecap;includingmeltwatercanyonsorcoulees.

Icefields Areasoficeaccumulationshowingnivationlandforms,butlackingclassicglaciallandforms.

IceSheetMargin Sculptedbyiceanddepositionofdriftandloessalongthemaximumextentboundaryofacontinentalicesheet.

IceSheetUplands Areaimmediatelyadjacenttoandinfluencedbyalargemassofglacierice,e.g.acontinentalglacier(largerthananicecap)

Intermountain Areasbetweenmountains.InterplainValleys Valleysthatcross-cutplains,suchasvolcanicplains,dueperhaps

toerosionaland/ortectonicprocesses.InwashPlain Abroad,gentlyslopingsheetofinwashdepositedbymeltwater

sourcedfromstagnantglacialice,thesurfaceofabroadbodyofinwash.

Landslides Massmovementdepositsandlandformswithrotationaltotranslationalstylesofslopefailure.

LavaFlows Alateral,surficialoutpouringofmoltenlavafromaventorafissure;also,thesolidifiedbodyofrockthatissoformed

Lowland **SeeMeybeckdefinitionbelowMaar Alow-relief,broadvolcaniccraterformedbymultipleshallow

explosiveeruptions.Itissurroundedbyacraterring,andmaybefilledbywater

MarinePlatform Anactivelyforminglandformgroupwithsimilarforms(esp.sanddunes,marine/estuarinesedimentdeposits,seacliff)andinternalcharacteristicsofmarineterraces;thelowestmarineterrace.


6

MarineTerrace Anarrow,gentlyslopingconstructionalcoastalstripextendingseawardorlakeward,andveneeredbyasedimentarydeposit;esp.awave-builtterrace.Or,astrippedwave-cutplatformthathasbeenexposedbyupliftorloweringofthewaterlevel;anelevatedwave-cutbench.(BJ1995,FSGeomorph)

MeanderBelt Adeeptoverydeeplyincisedmeanderplain;similarlandformstoameanderplainexceptmostaregreatlyexaggeratedinreliefandunderlainbybedrock.

MeanderPlain Thezonealongavalleyflooracrosswhichameanderingstreamshiftsitschannelfromtimetotime,specificallytheareaofthefloodplainincludedbetweentwolinesdrawntangentiallytothetheextremelimitsofallfullydevelopedmeanders.Itmaybefrom15to18timesthewidthofthestream(BJ1995,FSGeomorph)

Meltwatercanyons/coulees Landformssculptedbyglaciofluvialprocessinsubglacialandepiglaciallocations.Typicallyrecognizedasvalleyswithunderfitstreamsorwindgapsacrosswatersheddivides.

Midlands Landscapeintermediatetolowlandsanduplands.Moraine Amound,ridge,orotherdistinctaccumulationofunsorted,

unstratifiedglacialdrift,predominantlytill,depositedchieflybydirectactionofglacierice,inavarietyoftopographiclandformsthatareindependentofcontrolbythesurfaceonwhichthedriftlies.

Mountain **SeeMeybeckdefinitionbelowMountainfront Pronouncedmountainslopeorsetofplanartosomewhatplanar

slopesfacingaplainorotherareaoflowereelevationandlowrelief.

MountainValley Valleywithinandorientedparalleltothecrestofamountainrange,suchasacrestalchasmorgraben.

Mountainside Slopesofmountainousarea,extendingfrombelowthesummittoalowerposition.

OutwashPlain Abroad,gentlyslopingsheetofoutwashdepositedbymeltwaterstreamsflowinginfrontoforbeyondaglacier,andformedbycoalescingoutwashfans;thesurfaceofabroadbodyofoutwash(BJ1995,FSGeomorph)

PeatLowlands Areaoflowtopographicalreliefwithinternaldrainageandhighwatertableorsurfacewaterevident.ofpeatormuckaccumulationisknownorlikelihoodishigh.

Piedmont Lyingorformedatthebaseofamountainormountainrange;e.g.apiedmontterraceorapiedmontpediment.Anarea,plain,slope,glacier,orotherfeatureatthebaseofamountain;e.g.afoothillorabajada.(BJ1995,FSGeomorph)

Plain **SeeMeybeckdefinitionbelowPlateau **SeeMeybeckdefinitionbelowPlatform **SeeMeybeckdefinitionbelowPumiceFan Fan-shapeddepositofwater-transportedpumice,occuringatthe

baseofatopographicfeaturewherethereisaslopebreak


7

PumicePlain Areaoflowreliefandlowroughness(seeMeybeckdefinitionbelow)blanketedwithasubstantialthicknessofpumicefromalocalventsource

Scours Thepowerfulandconcentratedclearinganddiggingactionofflowingair,water,orice,esp.thedownwarderosionbystreamwaterinsweepingawaymudandsiltontheoutsidecurveofabend,orduringtimeofflood.

ScoursandDeposits Aprocessofalternateexcavationandrefillingofachannel,asbyastreamorthetides;especiallysuchaprocessoccurringintimeofflood,whenthedischargeandvelocityofanaggradingstreamaresuddenlyincreased,causingthediggingofthenewchannelsthatbecomefilledwithsedimentwhenthefloodsubsides.

ShieldCrest Crestalareaofashieldvolcano,comprisingpeakandshoulder.ShieldVolcano volcanointheshapeofaflatteneddome,broadandlow,builtby

flowsofveryfluidbasalticlavaland/orpyroclasticflows(modifiedBJ1995,FSGeomorph)

Tablelands Generaltermforabroad,elevatedregionwithanearlylevelorundulatingsurfaceofconsiderableextent;or,aplateauborderedbyabruptclifflikeedgesrisingsharplyfromthesurroundinglowland;amesa.(BJ1995,FSGeomorph)

Terrace Astep-likesurface,borderingavalleyfloororshoreline,thatrepresentstheformerpositionofafloodplain,lakeorseashore.Thetermisusuallyappliedtoboththerelativelyflatsummitsurface(tread),cutorbuiltbystreamorwaveaction,andthesteeperdescendingslope(scarp,riser)gradedtoalowerbaseleveloferosion.

Uplands Ageneraltermforhighlandoranextensiveregionofhighland,especiallyfarfromthecoastorintheinteriorofacountry.Thehighergroundofaregion,incontrastwithavalley,plain,orotherlow-lyingland(BJ1995,FSGeomorph)

Valley Anylow-lyinglandborderedbyhigherground;anelongate,relativelylarge,gentlyslopingdepressionoftheEarth'ssurface,commonlysituatedbetweentwomountainsorbetweenrangesofhillsormountains,andoftencontainingastreamwithanoutlet.Itisusuallydevelopedbystreamerosion,butmaybeformedbyfaulting.Abroadareaofgenerallyflatlandextendinginlandforaconsiderabledistance,drainedorwateredbyalargeriverandit'stributaries.(BJ1995,FSGeomorph)

ValleyBottoms Thecomparativelybroad,flatbottomofavalley;itmaybeexcavatedandrepresentthelevelofaformererosioncycle,oritmaybeburiedunderathincoverofalluvium.

Volcano Aconicalhilloflavaand/orpyroclasticsthatisbuiltuparoundavolcanicvent(BJ1995,FSGeomorph)

VolcanoMountains regioncharacterizedbymountainsofvolcanicorigin,whichareanypartoftheearth'scrusthigherthanahill,sufficientlyelevatedabovethesurroundinglandsurfaceofwhichitformsaparttobe


8

worthyofadistinctivename,characterizedbyarestrictedsummitarea(asdistinguishedfromaplateau),andgenerallyhavingcomparativelysteepsidesandconsiderablebare-rocksurfaceofvolcanicorigin(BJ1995,FSGeomorph)

MeybeckMountainModelThefollowingtermsaredefinedbasedontheMeybeckmountainmodel,whichusesdegreeofsurfaceroughnessandmeanelevationtodevelopastandardizedglobalclassification(Meybeck,M.,P.GreenandC.Vorosmarty.2001.ANewTypologyforMountainsandOtherReliefClasses:AnapplicationtoGlobalContinentalWaterResourcesandPopulationDistribution.MountainResearchandDevelopment,21(1):34-45).Roughnessandmaximumaltitudearedescribedataresolutionof30x30'.ReliefRoughness(RR)=maxminusminimumelevationpercelldividedbyhalfthecelllengthinmeters/kilometer.Hill(Meybeck) Allroughterrains(20<RR<160)atlowaltitude(200-500mean

elevation)Lowland(Meybeck) Restrictedtomaximummeanelevations<200m;verysimilarto

plainsbuthavearelativelygreaterroughnessduetominorormoderatevalleyincisions

Mountain(Meybeck) Definedbymeanelevation,exceeding500m,roughnessexceeds20atlowandmediumaltitudes(500-2000m)and40athighandveryhighaltitudes(2000-4000mand4000-6000m)

Plain DefinedprimarilybysubhorizontalreliefPlateau Lowormediumroughness;lowplateausareveryflatterrainwhile

highplateausmaybepoorlydissected(Meybeck).Anycomparativelyflatareaofgreatextentandelevation;specificallyanextensivelandregionconsiderablyelevated(morethan150-300minaltitude)abovetheadjacentcountryorabovesealevel;itiscommonlylimitedonatleastonesidebyanabruptdescent,hasaflatornearlysmoothsurfacebutisoftendissectedbydeepvalleysandsurmountedbyhighhillsormountains,andhasalargepartofitstotalsurfaceatornearthesummitlevel.Aplateauisusuallyhigherandhasmorenoticeablereliefthanaplain(itoftenrepresentsanelevatedplain),andisusuallyhigherandmoreextensivethanamesa;itmaybetectonic,residual,orvolcanicinorigin(BJ1995,FSGeomorph)

Platform Definedbyintermediatealtitude(200-500m,higherthanplains)andintermediateroughness(5-20).Canbeconsideredverylowaltitudeplateaus.

LandformGroupsofthePacificNorthwest-StructuralPatternQualifiersTerm Description

9

Broad Surfacemorepronouncedinarealextentthanrelief.Broadcrested Weaklydefinedridgelineborderedbylow-tomoderately-

slopingshoulders.CraggyDissected

Rough,ruggedelevatedsurfacefullofcrags.Havingahighreliefroughness,mainlyresultingfromstreamsystemscrossingthelandscape,resultinginarepeating"V-like"planviewofridgesandvalleys.

Faceted Havingflatfaceswithsharpangularboundariesbetweenfaces,indicativeofcompetent,crystallinebedrock

Incised Streamsareentrenchedinthesurroundinglandformandnotnecessarilyconnectedtoafloodplain.Thelandformmayhavealowsurfaceroughnessandlikelylacksthe"V-like"planviewcommonwithdissectedlandforms

Radial Radiatingdrainagedivergesawayfromacentralhighpoint,typicallyonaconicalfeaturesuchasavolcano

Reticulated Areadominatedbyobviousjointtrellis,rectangularorangulardrainagepattern.

RugoseSharpcrested

Surfacefullofwrinkleswithsunkendrainages.Drainagesideslopesareplanarconcave.Well-definedridgelineborderedbyrecognizableshouldersandorbackslopes.

Shattered Areawithdrainagepatterncharacterizedasgreatlyrandomizedandangulate.

Sinusoidal Havingsinuousshapedgroupsoflandformsoroutermapboundary.

Smooth Planarsurfacewithminortonodiscernablelandformsresolvableatoriginalscaleofmapping.

Smoothcrested Undefinedridgelineborderedbylow-slopingshoulders;lowrelief,convexo-planarsurfaceunderliesdrainagedivide.

Smoothtop Broad,low-slopingtoflatcrestalareasofridges.Stratal Megalandformsresultingfromcorrasionoftiltedgeological

strata,showinglandforms(flatirons,triangularfacets,dipslopes)indicativeofindividualbedstoformations.Synonyms:cuestaformandstructurallycontrolledslopes.

SulcateTerraced

Surfacewithlongitudinalfurrows,crestsaresmoothlyconvexandswalesarev-shaped.Drainagesideslopesareplanarconvex.Havingrepeatinglandformpatternsoftreadsandrisers

VerrucatedWashboard

Surfacescoveredbywartyorlumpyelevations.Thewartsorlumps(‘knockers’inCalifornia’sFranciscanTerrane)areresolvableatthescaleatwhichthelandformmapisproduced.Hassomesimilarinterpretationsas‘hummocky,’whichisreservedforareasofknownlandsliding.Regularlyspaceddrainagesandridgeswithmirrorsymmetryofdepthsandheights,respectively;analogoustoalaundrywashboardofold.

LandformGroupsofthePacificNorthwest-GeomorphProcessQualifierTerm Description

10

Ashmantled Blanketedwithsubstantialthickness(>18inches)ofash-sizedparticles(finerthan0.1inch)fromlocalventsources

Ashy Blanketedwiththin(<18inches)ofash-sizedparticles(finerthan0.1inch)fromlocalventsources

Collapsed Indicativeoflarge-arealandslides/masswasting,slumpandsourcecanbeidentified;drainagepatternsmaybeinterrupted

Eroded Wornawaybyrunningwater,waves,movingice,orwind(deflationorabrasion),orbysuchprocessesasmasswastingandcorrosion(Bloom,1991,FSGeomorph)

Faulted Areaoffracturinganddisplacementwheretworockmasseshaveslidpasteachother

Fluvial Oforpertainingtostreams;producedbystreamorriveractionFluviolacustrine Materialtransported,sortedanddepositedbyflowingstreams

intolakesystems,wherefurthersortingmayoccurGlacial Pertainingtodistinctiveprocessesandfeaturesproducedbyor

derivedfromglaciersandicesheets,asinglaciallakesorglacialerosion(BJ1995,FSGeomorph);

Glacialscoured Areaofbarerockresultingfromtheabrasiveactionofrockfragmentsembeddedinthebaseofamovingglacier(myowndefinition)

Glaciated Pertainingtoaformerlyglacier-coveredsurface,especiallyonethathasbeenmodifiedbytheactionofaglacieroranicesheet

Glaciofluvial Stratifiedmaterialmovedbyglaciersandsubsequentlysortedanddepositedbystreamsflowingfromthemeltingice.(NRCSGlossary,HP)

Glaciolacustrine Materialrangingfromfineclaytosandderivedfromglaciersanddepositedinglaciallakesbywateroriginatingmainlyfromthemeltingofglacialice.Manyarebeddedorlaminatedwithvarvesorrhythmites.

Glaciovolcanic Depositsand/orlandformsderivedfrommixedsourcesofglacialandvolcanic,includingash-on-icesourceddepositsandsubglacialeruptiveventsandflows.

Hummocky Uneven,irregularorundulatinggroundsurfacewithmanysmallhillsandswales;maybeindicativeofdeep-seatedrotationalsoilmovementbutnotnecessarilyso(mydefinition)

IceMargin SculptedbyiceanddepositionofdriftandloessalongthemaximumextentboundaryofaMountainIceCaporContinentalIceSheet.

Lacustrine Pertainingto,producedby,orformedinalakeorlakes.MegafloodScoured Soilandunconsolidatedgeologicsedimentsremoved/swept

awaybyMissoulaFloodsfloodwatersOutwashScoured Areascouredofsoilandunconsolidatedgeologicsedimentsby

glacialmeltwatersandlocallyaccumulativeofdrift,particularlystratifiedoutwash.

LandformGroupsofthePacificNorthwest-GeomorphProcessQualifierTerm Description

11

Paraglacial Influenced/directlyconditionedbyglaciationanddeglaciation,thoughtheareaisnotindirectcontactwithglacialiceorinfluencedbycold-climateprocessesaswithperiglaciallandscapes;featuresareconstructedbygeomorphicprocessesactiveduringthetransitionfromglacialtopost-glacialconditions(mydefinition)

Periglacial Pertainingtoprocesses,conditions,areas,climates,andtopographicfeaturesoccurringattheimmediatemarginsofglaciersandicesheets,andinfluencedbycoldtemperatureoftheice.

Pumiced Coveredwithpumice,rockfragments>2mmindiameter,madeoflight-colored,vesicular,glassyrockcommonlyhavingthecompositionofrhyolite.Thematerialcommonlyhasaspecificgravityof<1.0andistherebysufficientlybuoyanttofloatonwater.

Volcanic ReferringtotheprocessesbywhichmagmaanditsassociatedgasesriseintothecrustandareextrudedontotheEarth'ssurfaceandintotheatmosphere;thestructuresrocksandlandformsproduced.

Volcanofluvial Depositsand/orlandformsderivedfrommixedfluvialandvolcanicprocesses,includingmudflowdeposits.

GeomorphologyofthePacificNorthwest–MorphometryQualifiers

12

Thefollowingaremorphometryparameters,definitionsandvalidvaluesusedintheUSFSclassification,withsomeadditionsandmodifications.SlopeShape-Referstotheshape(horizontaland/orvertical)ofthelandsurfaceValue MeaningCV Concave(alsodepression)CX Convex(alsoraised)L Linear/Planar(alsostraight,even,smooth)P Patterned-reliefofhummocksandswaleswithinseveralfeet)U Undulating(alsorolling)-patternofoneormorelowreliefridgesorknollsanddrawsB Broken-cliffs,knobs,and/orbenchesinterspersedwithsteeperslopes-generally

characterizedbysharp,irregularbreaksX Mixed

GroundSurfaceShape-Shapeofthegroundsurface(asopposedtothelandsurface).Maybefurtherdescribedaccordingtothetypeoffeaturescausingtheshapebyatermfromthemicrofeaturetable.

Value MeaningC CollapsedE ErodedF FaultedH HummockyU Uniform

DissectionFrequencyClass-Thefrequencyclassfordissectionsinlandformswithslopecomponents.Value Meaning(at1:100,000scale)U Undissected(0channels/mile)S SlightlyDissected(1-2channels/mile)M ModeratelyDissected(2-5H HighlyDissected(>5channels/mile)

DissectionDepthClass-Thedissectiondepthclassforlandformswithslopecomponents.Value MeaningS ShallowlyincisedI IncisedD Deeplyincised(akaDeep)V Verydeeplyincised(akaUltradeep)R Rugged-Havingtwoormoredissectiondepthclasses


13

DrainagePattern-Theconfigurationorarrangementinplanviewofthenaturalstreamcoursesinanarea.

Value MeaningDN Dendritic-TypepatternresemblesspreadingoakorchestnuttreeDNSD Subdendritic-minorsecondarycontrolDNPN Pinnate-Adendriticdrainagepatterninwhichthemainstreamreceivesmanycloselyspaced,

subparalleltributariesthatjoinitatacuteangles,resemblinginplanafeather;itisbelievedtoindicateunusuallysteepslopesonwhichthetributariesdeveloped.Foundinfine-textured,easilyerodiblematerials.

DNAS Anastamotic-Pertainingtoanetworkofbranchingandrejoiningchannelpatternofabraidedstream.Foundonfloodplains,deltasandtidalmarshes.

DNSD Distributary-Adivergentstreamflowingawayfromthemainstreamandnotreturningtoit,asinadeltaoronanalluvialfan.Itmaybeproducedbystreamdepositionchokingtheoriginalchannel

PR Parallel-Adrainagepatterninwhichthestreamsandtheirtributariesareregularlyspacedandflowparallelorsubparalleltooneanotheroveraconsiderablearea.Itisindicativeofaregionhavingapronounced,moderatetosteepuniformslopeandahomogeneouslithologyandrockstructure.Alsofoundinareaswithparallel,elongatelandforms.

PRSP Subparallel-Foundonintermediateslopesorcontrolledbysubparallellandforms.PRCO Colinear-Occurbetweenlinearlandforms,suchasthoseobservedinerodedloessplainsand

sandridges.TR Trellis-Adrainagepatterncharacterizedbyparallelmainstreamsintersectedatornearlyat

rightanglesbytheirtributaries,whichinturnarefedbyelongatedsecondarytributariesparalleltothemainstreams,resemblinginplanthestemsofavineonatrellis.Itiscommonlydevelopedwherethebevelededgesofalternatinghardandsoftrocksoutcropinparallelbelts,asinarejuvenatedfolded-mountainregionorinamaturelydissectedbeltedcoastalplainoftiltedstrata;itisindicativeofmarkedstructuralcontrolemphasizedbysubsequentandsecondaryconsequentstreams.

TRST Subtrellis-Parallelelongatelandforms.TRDT DirectionalTrellis-Occursongentlehomoclinesorgentleslopeswithbeachridgesorother

linear,apparentlyaccretionarylandforms.TRRT RecurvedTrellis-Occursonplungingfolds.TRJT JointTrellis-Occursinareashavingstraightparallelfaultsorjointsorothertypelithological

contacts.RC Rectangular-Adrainagepatterninwhichthemainstreamsandtheirtributariesdisplaymany

right-anglebendsandexhibitsectionsofapproximatelythesamelength;itisindicativeofstreamsfollowingprominentfaultorjointsystemsthatbreaktherocksintorectangularblocks.Itismoreirregularthanthetrellisdrainagepattern,asthesidestreamsarenotperfectlyparallelandnotnecessarilyasconspicuouslyelongated,andsecondarytributariesneednotbepresent.

RCAN Angulate-Occursinareashavingjointsandfaultsatotherthanarightangle.RD Radial-Adrainagepatterninwhichconsequentstreamsradiateordivergeoutward,likethe

spokesofawheel,fromahighcentralarea;itisbestdevelopedontheslopesofayoung,unbreacheddomalstructureorofavolcaniccone.

RDCN Centripetal-Occursincraters,calderasandotherdepressions.


14

AN Annular-Adrainagepatterninwhichsubsequentstreamsfollowaroughlycircularorconcentricpathalongabeltofweakrocks,resemblinginplanaring-likepattern.Itisbestdisplayedbystreamsdrainingamaturelydissectedstructuraldomeorbasinwhereerosionhasexposedrimmingsedimentarystrataofgreatlyvaryingdegreesofhardness.

MB Multibasinal-Drainagepatternexpressedinareashavinghummockysurficialdeposits,differentiallyscouredordeflatedbedrock,areasofrecentvolcanism,limestonesolutionorpermafrostwherethereisamultipledepressionpattern.

MBGD GlaciallyDisturbed-Glacialerosionordeposition.MBKS Karst-Limestoneorotherlithologypronetodissolutionandmasscollapseduetosolutional

erosionofmass.MBTK Thermokarst-PermafrostMBEB ElongateBay-Coastalplainsanddeltas.CT Contorted-Apatternlackingregionalorderliness,discontinuityofridgesandvalleysand

generallysmallerscale.

TopographicalModifierValue MeaningH High-Landsurfaceispronouncedlyhigherinelevationthanneighboringareaorotherland

surfacesofsimilarclass.L Low-Landsurfaceisrelativelylowerinreliefthanneighboringareaorotherlandformgroups

ofsimilarclass.D Deep-Landsurfaceisobviouslydeeperinreliefthanneighboringareaorotherlandform

groupsofsimilarclass.U Ultradeep-Landsurfaceispronouncedlydeeperinreliefthanneighboringareaorother

landformgroupsofsimilarclass.

SurficialProcesses(PROC1[=SurficialProcess#1],PROC2,PROC3;Sp1[=SurficialProcess#1],Sp2)Code Initial SurficialProcess0 W Activewaterbodies;rivers,lakesandocean.1 E Eolian2 F Fluvial3 G Glacial4 L Lacustrine5 O Marine(Ocean)6 M Masswasting,includingcolluvium7 T Tectonicorstrata(Geologicalstructure)8 V Volcanic9 X Mixed


15

ConstructionModifier(LfA_CON[LandformAssoc.construction],LfG_CON[LandformGroupconst.])Value Meaning3 Geologicallyrecentconstructionoflandformisevident.Freshlandformsindicativeofnew

constructionoflandsurfacebydepositionofsediments,tephraorothermaterials.Minorerosion,suchasactiveriverchannels,maybeincludedinthisclass.Originallandform(s)(inferred)is/arewellpreservedinmuchofthelandformmapunit.

2 Sameasvalue3,exceptfreshnessornewconstructionareinevidentorweatheringanddegradationoflandformhasoccurred.Originallandform(s)(inferred)is/aremoderatelypreservedinmuchofthelandformmapunit.

1 Sameasvalue2,exceptitisevidentthatweatheringanddegradationoflandformhasoccurred.Originallandform(s)(inferred)is/arepoorlypreservedinmuchofthelandformmapunit.

0 Nothingremainsoftheoriginalconstructionalorerosionalsurface.Originallandform(s)(inferred)is/arenotpreservedinanypartofthelandformmapunit.

-1 Sameasvalue-2,exceptitisevidentthatweatheringandaggradationonlandformhasoccurred.Originallandform(s)(inferred)is/arepoorlypreservedinmuchofthelandformmapunit.

-2 Sameasvalue-3,exceptfreshnessornewdestructionareinevidentorweatheringandaggradationonlandformhasoccurred.Originallandform(s)(inferred)is/aremoderatelypreservedinmuchofthelandformmapunit.

-3 Geologicallyrecenterosionoflandformisevident.Freshlandformsindicativeofnewerosionoflandsurfacebyscouringofsediments,rockorothermaterials.Minordeposition,suchasactiveriverfloodplain,maybeincludedinthisclass.Originallandform(s)(inferred)is/arewellpreservedinmuchofthelandformmapunit.


16

Provisional‘Global’KeytoRaster/GridMapofLandformsintheAreaoftheWillametteNF Thesehaveyettobelocallyreclassedtomorespecificlandformname. DraftSummer2011JayNoller,OregonStateUniversityBasedonWeissLandformModel(forArcView)LandformsDominantlyRelatedtoFluvialErosionorDeposition1 CANYONSandDEEPLYINCISEDSTREAMS(Fluvialdeposits,localrockfalldepositswherewalls

havetoppledorcollapsed)

2 MIDSLOPEDRAINAGESandSHALLOWVALLEYS(Fluvialdepositspredominant)

3 UPLANDDRAINAGESandHEADWATERS(Fluvio-colluvialdepositspredominant)

LandformsDominantlyRelatedtoGlaciation

4 U-SHAPEDVALLEYS(Glacialdepositsandlandformspredominant;includesvalleybottoms,valleymid-slopesandlowerglacialtroughwalls)

LandformsofMultiplePotentialOrigins

5 PLAINS

6 OPENHILLSLOPES

7 UPPERHILLSLOPESandMESAS

8 LOCALRIDGESandHILLSINVALLEYS

9 MIDSLOPERIDGESandSMALLHILLSINPLAINS

10 PEAKS,MOUNTAINTOPS,andHIGHRIDGES

GeomorphologyofthePacificNorthwest

17

References

Bates,R.L.,andJackson,J.A.,eds.,(1987,1995);GlossaryofGeology,2nded.,AmericanGeologicalInstitute,Alexandria,Virginia.[BJ1995]

Davis,C.,etal.(2004)LandtypeassociationsofnorthcentralWashington.USDA-USFSTechnicalReport,Wenatchee,WA.

Haskins,D.M.,etal.(1998)AGeomorphicClassificationSystem,v.1.4,U.S.D.A.ForestServiceGeomorphologyWorkingGroup.USDA-USFSTechnicalReport,Washington,DC.[FSGeomorph]

Tuttle,S.D.(1975)Landformsandlandscapes.Dubuque,Iowa,W.C.BrownPublishers,152pp.

Geomorphology of the Pacific Northwest - Ecoshare · PDF fileGeomorphology of the Pacific...

Documents

Transcript of Geomorphology of the Pacific Northwest - Ecoshare · PDF fileGeomorphology of the Pacific...