I

nmetamorphosedlimestone,

dolostone,andmarble

Inmoderatelytosteeplydippingbeds

ofcarbonaterock

Ingentlydippingtoflat-lyingbedsof

carbonaterock

Ingentlydippingtoflat-lyingbedsof

carbonaterockbeneathan

overburdenofnoncarbonatematerial10ft(3m)

to200ft(60m)thick

Inmoderatelytosteeplydippingbedsofgypsum

Ingentlydippingtoflat-lyingbedsofgypsum

FISSURES,TUBES,ANDCAVESOVER1,000FT(300M)

LONG;50FT(15M)TOOVER250FT(75M)VERTICAL

EXTENT

FEATURESANALOGOUSTOKARST

Inmetamorphosedlimestone,

dolostone,andmarble

Inmoderatelytosteeplydipping

carbonaterock

Incrystalline,highlysiliceous

intenselyfoldedcabonaterock

Ingentlydippingtoflat-lying

carbonaterock

Ingentlydippingtoflat-lyingbeds

ofcarbonaterockbeneathanoverburden

ofnoncarbonatematerial10ft(3m)

to200ft(60m)thick

FISSURES,TUBES,ANDCAVESGENERALLYLESS

THAN1,000FT(300M)LONG;50FT(15M)OR

LESSVERTICALEXTENT

Inmoderatelytosteeplydippingbedsofgypsum

Ingentlydippingtoflat-lyingbedsofgypsum

Incarbonatezonesinhighlycalcicgranite(Alaskaonly)

Inmoderatelytosteeplydippingbedsofcarbonate

rockwithathincoverofglacialtillandfrost-derived

residualsoil(Alaskaonly)

Ingentlydippingtoflat-lyingbeds

ofgypsumbeneathandoverburden

ofnongypsiferousmaterial10ft(3m)

to200ft(60m)thick

Incrystalline,highlysiliceous

intenselyfoldedcarbonaterock

Inmoderatelytosteeplydippingbeds

ofcarbonaterock

Ingentlydippingtoflat-lyingbedsof

carbonaterock

FISSURES,TUBES,ANDCAVESGENERALLYABSENT;

WHEREPRESENTINSMALLISOLATEDAREAS,LESS

THAN50FT(15M)LONG;LESSTHAN10FT(3M)

VERTICALEXTENT

Fissuresandvoidspresenttoadepthof250ft(75m)

ormoreinareasofsubsidencefrompipinginthick

unconsolidatedmaterial

Fissuresandvoidspresenttoadepthof50ft(15m)inareas

ofsubsidencefrompipinginthick,unconsolidatedmaterial

Fissures,tubes,andtunnelspresenttoadepthof250ft

(75m)ormoreinlava

Fissures,tubes,andtunnelspresenttoadepthof50ft

(15m)inlava

Areasinwhichextensivehistorical

susidencehasoccurred

	ENGINEERINGASPECTSOFKARST

	By

	WilliamE.Davies

Distinctivesurficialandsubterraneanfeaturesdevelopedbysolutionofcarbonateandother

rocksandcharacterizedbycloseddepressions,sinkingstreams,andcavernopeningsare

commonlyreferredtoaskarst.ThetermwasusedfirsttodescribetheregionofCarsoin

northeasternItalyandnorthernYugoslavia,wheresolutionlandscapewasstudiedinthe19th

century.Originallythetermdefinedsurfacefeaturesderivedbysolutionofcarbonaterocks,but

subsequentusehasbroadenedthedefinitiontoincludesulfates,halides,andothersolublerocks.

Thetermhasbeenexpandedalsotocoverinterrelatedformsderivedbysolutiononthesurface

inthesubsurface.Afurtherexpansionoftheconceptofkarstwastheintroductionoftheterm

"pseudokarst"todesignatekarstliketerrainproducedbyprocessesotherthanthedissolutionof

rocks(BurgerandDubertret,1975).Whenusedinitsbroadestsense,thetermencompasses

Shaftsarepresentinmultiple-levelcavesandinsomesingle-levelcaves.Thedeepestshaftsare

about1,000ft(300m)deep,butinmostcavestheyarelessthan300ft(90m)deep.Mostshafts

are30ft(10m)orlesswide.Inmultiple-levelcaves,shaftsconnectlevels;inothercaves,the

shaftsarepitswithnoapparentconnectionatthebase.Shaftsareirregularinshape;some

resemblefunnels,andothersareshapedlikecylinders.Domepitsarecylindricalshaftsthat

developupwardfromapassagetowardsthesurfaceoftheEarth.Domepitsareupto50ft(15

m)wideandextendupwardforasmuchas150ft(45m).Theirwallsareuniform.Domepitsare

cappedbyacoverofcarbonaterocks10to50ft(3to15m)thick.Inmanydomes,thecapshave

collapsedandleftvertical-sidedopenpits.

Virginia,WestVirginia,Kentucky,Tennessee,Alabama,Missouri,Texas,andNewMexico

containhundredsofcaves,eachofwhichhasoveramileofpassages.Atleastonecavernsystem

ineachoftheseStateshas10tomorethan100mi(16to160km)ofpassages.Thelargest

knownsystemisFlintRidge-MammothCaveinKentucky(Brucker,1979),withover200mi

(320km)ofpassagewaysinanareaof362mi(902km).

Solutiontubeswithopeningsasmuchas1ft(0.3m)wideandirregularalignmentoccupy

portionsofthecarbonatebedrock.Insomecases,thetubesconnectwithcaves.However,the

tubesgenerallylackthesystematicpatternsthatarecommonindevelopmentofcavernpassages.

Thesetubesapparentlypredatecaverndevelopment.Althoughmosttubesareseldomlongerthan

afewhundredfeet,theyareinterconnectedandcommonlyactasconduitsforsubsurface

drainage.Duringfreezingweather,waterfromtubescancauselargebuildupsoficewhere

excavationsintersectthetubes.Atothertimes,thetubesleadtofloodingofexcavationsand

leaksinreservoirsandcontributetoweakeningofretainingwalls.

Fissures(alsoreferredtoasopenjoints)upto1ft(0.3m)wideresultfromlimitedsolutionalong

joints,fractures,andbeddingplanes.Fissuresoccurinvariousattitudesfromverticaltogently

inclinedandgenerallyareinrepetitivegeometricalpatternsorsets.Fissuresformsystemsthat

mayextendforseveralthousandfeethorizontallyandover300ft(90m)vertically.Some

fissuresorpartsoffissuresarefilledwithconsolidatedclay-siltandclay-gravelthatsealthem.

Theseals,however,arealteredincontactwithwaterandcanberemovedbyrunningwater.

Fissuresarecommonlyconduitsforsubterraneanstreams.Inaddition,theycancauseserious

engineeringproblems,suchasreservoirleakageandinstabilityofcuts,bridgeabutments,piers,

anddamfoundationsandabutments.

Thedepthtowhichsolutionopeningsoccurdependsonreliefinanarea,thicknessofsoluble

rock,andgeologicstructure.Theconfigurationanddepthofthewatertable,insomecases,are

controllingfactors.Groundwaterinkarstterraingenerallyisfoundinexistingopeningsthat

extendtenstohundredsoffeetbelowthewatertable.InthemountainousareasoftheWestern

UnitedStates,theknownverticalextentofsolutionopeningsisasmuchas1,100ft(330m).In

theEasternUnitedStates,wherereliefisless,theverticalextentisgenerallylessthan400ft

(120m),withamaximumof650ft(200m).Beneathmanybroadrivervalleys,solutionfeatures

incarbonaterocksarepresenttoadepthofabout100ft(30m)inboththeEasternandWestern

UnitedStates.

Surfacesubsidence(sinkholedevelopment)occursmostcommonlyinareaswhereground-water

conditionsarealteredbyexcessivepumpingorbydiversionofsurfacedrainage.Subsidence

generallyinvolvesweatheredbedrockandsoilthatbridgecaverns,subterraneangalleries,and

domepits.Thecollapseiscausedbylossofsupportresultingfromthereductionofhydrostatic

pressureofgroundwater,bysapping,andbypiping.Mostsubsidenceformsshallow,steep-sided

depressionsupto100ft(30m)wideandupto20ft(6m)deep.However,inFloridaandcentral

Alabama,recentsubsidencehasresultedinnearlyverticalsidedsinkholesupto425ft(130m)

wideand150ft(45m)deep.

Areasoflocalsubsidencecausedbyminingoperationsandregionalsubsidencecausedby

withdrawalofgroundwaterandpetroleuminthick,unconsolidatedsedimentshavenotbeen

includedonthemapofsubterraneanaspectsofengineeringgeologyofkarstandpseudokarst

becausenaturalprocessesareinvolvedonlyinasubordinatewayindevelopmentofthese

phenomena.Theproblemsofthesetypesofsubsidencearecomplex,andtheareasinvolvedare

soextensivethattheyarebesttreatedassubjectsforanothermap.

IntheNewEnglandStates,solutionterrainisconfinedtocrystallinelimestonesandmarbles

mainlyinnortheasternMaine,westernVermont,andwesternMassachusetts.Solutionfeaturesin

theseareasareprimarilynarrowfissuresgenerallylessthan200ft(60m)longandlessthan30ft

(10m)deep.AfewsmallcavesareknowninwesternVermontandintheBerkshireMountains

ofwesternMassachusetts.IneasternVermontandmuchofMaine,carbonaterockshighinsilica

andotherimpurities'arecommonly,yetincorrectly,referredtoaslimestone.Solutionfeatures

aregenerallyabsentintheserocks.

IntheAppalachianHighlands,threemajorgroupsofcarbonaterocksareinthekarstregions.The

GreatValley,intheeasternpartoftheHighlands,fromsoutheasternNewYorktocentral

Alabama,isalowlandupto26mi(42km)wideerodedacrossdolomite,limestone,andshaleof

CambrianandOrdovicianage,Regionally,andtosomeextendreflectingdifferencesindegreeof

karstdevelopment,theGreatValleyisdesignatedfromnorthtosouthastheKittatinny,Lehigh,

Lebanon,Cumberland,Hagerstown,Shenandoah,andTennesseeValleys.Alltypesofsolution

featuresarepresentintheGreatValley,withsmallcavesandfissuresinsoutheasternNewYork

andlikefeaturesincreasinginsizeandnumberssouthward.FromcentralVirginiasouthward,

largecaveswithover1mi(1.6km)ofpassagesineacharecommon,andfissuresextend

hundredsoffeetinlengthandover100ft(30m)indepth.Themajorgeologicunitsinvolvedin

karstdevelopmentintheGreatValleyaretheElbrook(Cambrian),Conococheague(Cambrian-

Ordovician),Beekmantown(Ordovician),andtheirequivalents.Allarefoldedwithsteepdips,

andoverturningiscommonalongtheeasthalfofthelowland.Faultsarenumerousandsome

majorfaultzonesextendover200mi(320km).Activesubsidenceisprevalentthroughoutthe

GreatValleyandisaresultprimarilyofalterationofthewatertable.Generally,thesubsidence

involvestheopeningofshallowfissuresandshaftsupto10ft(3m)indiameterinfarmland

throughremovalofsoilandthinrockcoveroverfissures,shallowcavernpassages,andsmall

domepits.MoreextensivesubsidenceisinprogressinthevicinityofAllentownandHarrisburg,

Pennsylvania,wherenumeroussubsidencedepressionsupto100ft(30m)indiameterhave

developed.InStaunton,Virginia,activesubsidencefromcollapseofrocksandsoilcovering

shallowcavesandfissureswasrecordedasearlyas1911.SubsidenceintheStauntonarea

resultedfromlarge-scalepipingofsinkholesoilsbyleakagefromsettlingbasinsandfrom

drawdownofthewatertable.IncentralAlabama,steep-sided,water-filledsinks,upto425ft

(130m)wideand150ft(45m)deep,haveformedrecentlybycollapseofweatheredlimestone

andthicksoilscoveringlimestone.

IntheareawestoftheGreatValley,asequenceoflimestonesintheUpperSilurian(Tonoloway)

andtheLowerDevonian(HelderbergGroup)formssubordinateridgesinsoutheastemNew

York,centralPennsylvania,easternWestVirginia,andwesternVirginia.Therockisfolded,and

dipsaresteep.Karstfeaturesincludefissuresextendingseveralhundredfeetverticallyandcaves

withupto1mi(1.6km)oflargepassageways.Subsidenceisuncommon,butthefissuresand

caveshavecausedproblemsinfoundationsandabutmentsofdams,incutsbecauseofunstable

wedges,andintunnelsthatencounterearthfillsinsolutioncavities.

AlongthewesternedgeoftheValleyandRidgeprovinceoftheAppalachianHighlands,several

largebasinlikelowlandsunderlainbyCambrianandOrdoviciancarbonaterocksoccur.The

lowlandsareerodedacrosslargeanticlineswithsteepdipsontheflanksandmoderatetosteep

plungesalongtheaxesoftheanticlines.IntheNittanyandKishacoquillasValleysof

Pennsylvania,andsomesmallervalleysdesignatedas"coves,"numerouscavesoccur,eachwith

passageways1,000to5,000ft(300to1,5!)0m)longThepassagesgenerallyare100ft(30m)or

lessbelowthesurface.Manyactassubterraneanfeedersthatcarryrunofffromadjacentridgesto

afewpointsofresurgence.Theresurgentpointsarelargespringswithadailyflowofupto1

milliongallonsormore(4millionormore).Fissuresarepresentbutseldomexceed200ft(60m)

indepth.Subsidenceisnotcommon,butdeepcutsandexcavationsaresubjecttouncontrollable

floodingifmajorsubterraneanconduitsareencountered.InGermanyValley,WestVirginia,

solutionfeatures,primarilymultiple-levelcavesandfissures,extendtodepthsof350ft(105m)

ormore.Drainageofmostofthisvalleyisbywayofonelargespring.Subsidencefromcollapse

ofsinkholesiscommon,andpotentialforsubsidenceexistsovernumerousdomepitsabove

caves.

TheAppalachianPlateau'sprovinceandadjacentpartsoftheInteriorPlainsinWestVirginia,

Kentucky,Tennessee,northernAlabama,andsouthernIndianacontainthemostintensely

developedkarstareasintheUnitedStates.ThekarsticcarbonaterocksareMississippianinage

andincludetheGreenbrierlimestone(WestVirginia)andtheGolconda,Ste.Genevieve.St.

Louis,andWarsawlimestonesandtheirequivalentselsewhere.Cavesgenerallycontain3,000ft

(900m)ormoreofpassageways.Multiple-levelcavesarenotcommon,butsomelargecave

systems,suchasFlintRidge-MammothCaveinKentuckyandOrganCaveinWestVirginia,

haveamultitudeofcomplexpassagewaysatvariouselevationsthatextendinaggregatefrom30

IntheLowerPeninsulaofMichigan,carbonaterocksareextensivebutareburieddeeplybeneath

glacialdeposits.SilurianlimestonesalongLakeHuronbetweenAlpenaandtheStraitsof

Mackinaccontainseverallargesinkholesupto1mi(1.6km)longand200ft(60m)deep.The

sinkholesareinterconnectedbyanextensivefissuresystem.Normally,thesinkholesarefilled

withwater,but,overtime,plugsinthefissuresystemfailandthelakesdrainthroughthe

subterraneanopenings.SubsidencegenerallydoesnotoccurintheLowerPeninsula.

OrdovicianlimestonescoverthesouthhalfoftheUpperPeninsulaofMichiganandextend

througheasternandsouthernWisconsin,easternIowa,andpartsofsoutheasternMinnesota.

Karsticfeaturesarepoorlydevelopedandconsistofsimplecaves,eachwithlessthan1,000ft

(300m)ofpassagewaysandlessthan50ft(15m)ofverticalextent.Fissuresdevelopedalong

jointlinesareinaboutthesamesizerangeasthecaves.InthevicinityofDubuque,Iowa,and

extendingintoadjacentWisconsinandIllinois,fissuresseveralhundredfeetlongandmorethan

300ft(90m)deephavebeenencounteredinlead-zincmines.Thefissurespossiblyarerelict

fromolderburiedkarst.Subsidencefromkarstfeaturesisrare,althoughsubsidenceovermines

isextensive.

TheOzarkPlateausprovinceandadjacentplainsinMissouriandnorthernArkansashave

extensivekarstareas.TheOzarksarealargeregionalstructuraldomewithsteepdipsalongthe

southernflank.ThedomebringsCambrianandOrdovicianlimestonesanddolomitestothe

surface.NorthandwestofthedomeareplainsunderlainbyMississippiancarbonaterocks

(Warsaw,StLouis,Ste.Genevieve,andequivalents).WithintheOzarks,caves,eachwith

passages1,000ft(300m)ormorelong,arecommon.Thepassagesinmostcavesextendtoa

depthoflessthan100ft(30m).Pits,formedbycollapseintocavernshaftsanddomepits,are

common,and,insouthernMissouri,activesubsidenceisextensive.Mostofthepitsarewater

filled.Fissuresover1,000ft(300m)longandmorethan300ft(90m)deeparepresentinmuch

ofthearea.Similarfissuresarenumerousinthelead-zincminingregioninsouthwestern

MissouriandadjacentOklahomaandArkansas.ThroughouttheOzarks,thecavesandfissures

giverisetoseriousproblemsinfoundationsandabutmentsofdamsandwithreservoirtightness,

stabilityofbridgepiers,andstabilityofcutslopes.Thepresenceoflargequantitiesof

subterraneanwaterisaproblemindeepfoundations.

TheNiobraraFormation(UpperCretaceous)anditsequivalentsarethemostwidespread

carbonaterocksinwesternKansas,easternNebraska,andsoutheasternSouthDakota.The

Niobraraisgenerallycoveredbymorethan50ft(15m)ofyoungersediments.Smallfissures,

lessthan1,000ft(300m)longandupto100ft(30m)deep,arepresent,buttheyarenot

commonandaregenerallyirregularlyspacedwith1,000ft(300m)ormoreofsolidrock

betweenfissures.

Saltbedsinsouth-centralandsouthwesternKansasformkarstareas.Fissuresareextensive,with

openingsmorethan1,000ft(300m)longandover300ft(90m)deep.Throughoutthesaline

rock,recentsubsidencehasresultedfromnaturalcauses,aswellasfromalterationofthewater

tablebysolutionminingandopenpitmining.

InwesternSouthDakotaandadjacentpartsofWyomingandMontana,PaleozoicandCretaceous

carbonaterocks,archedsteeplyupwards,encirclethestructuraldomethatformstheBlackHills.

CavesandopenfissuresarecommoninthePaleozoiccarbonaterocks.Afewcavescontain

manymilesofpassagesbutmostofthecavepassagesandfissuresintheBlackHillsareaonly

extendupto3,000ft(900m)inlengthandaregenerallylessthan150ft(45m)indepth.Closely

spacedsolutionjointsalsoareprevalent.

InwesternOklahomaandintheeasternpartoftheTexasPanhandle,extensiveareasofkarstic

gypsumoccur.Smallopenfissuresupto50ft(15m)deepand1,000ft(300m)longarepresent.

Passagesincavesingypsumaregenerallyofsimilarlengthanddepth.

TheEdwardsLimestone(Cretaceous)inwest-centralTexasformsanextensiveplateau.Large

cavesandfissuresarepresenttoadepthof600ft(180m),andbothfissuresystemsandpassages

ofsinglecavescommonlyextendformorethan1mi(1.6km).Boththecavesandfissures

containlargequantitiesofwaterintheirdeeperparts.

PermiancarbonaterocksincentralandsouthernNewMexicocontainnumerouswell-developed

karstfeatures.Cavesaregenerallyverylargeandcontainmilesofpassageswithaverticalextent

of1,000ft(300m)ormore.Fissuresareofsimilarsizeandareinterconnected,forming

networksthatextendforseveralmiles.Closelyspacedopenjoints,enlargedbysolution,and

numeroussmall,near-surfacesolutiontubescauseextensivetroubleinreservoirtightness

throughoutthiskarstarea.

InnorthernandcentralArizona,theKaibabLimestone(LowerPermian)anditsequivalentsare

karstic.NorthoftheGrandCanyon,subterraneanopeningsareprimarilywidelyspacedfissures

upto1,000ft(300m)longand250ft(75m)ormoredeep.SouthoftheGrandCanyon,the

fissuresaremorecloselyspacedandafewshallowcavesarepresent.EastofFlagstaff,thereis

anareaofopenfissures.Thesefissuresareover300ft(90m)deep,upto1,000ft(300m)long,

andupto3ft(1m)wide.TheycuttheCoconinoSandstone,aswellastheKaibabLimestone

(Colton,1938).

TheMadisonLimestone(Mississippian)liesunderkarstareasinwesternMontanaandadjacent

partsofIdahoandWyoming.Passagesinasinglecavearecommonlyupto2mi(3.2km)long.

Openfissuresupto1,000ft(300m)longandshallow,openjointsystemsarealsocommon.

Fissuresandcavernpassagesextendasmuchas1,000ft(300m)deep.Largequantitiesofwater

arepresentinthelowerpartsofthefissuresandinsomeofthedeepercavernpassages.Relict

karstfeaturesdevelopedduringtimesofdisconformityattheendoftheMississippianare

commonintheMadisonLimestone.Mostoftherelictfeaturesaresolutiontubes,caves,and

smallfissuresthathavebeenfilledwithyoungerdepositsthatarenowlithified.Becauseof

differencesinmaterials,residualopenings,andsecondarysolution,thesefeaturescangiveriseto

foundationproblemsandleakage.

KarstfeaturesinAlaskaarenotwellknown.Mostofthesefeaturesareshallow,swalelike

depressionsdevelopedinathincoverofresidualsoilandglacialtillthatliesoverintensely

foldedlimestone.Afewcaveopeningsareinlimestonebluffs,butmostcaveentrancesare

hiddenbyacoverofspalledrockfragments.Streamscrossinglimestoneterrainscommonly

disappearintothesoilmantleandresurgeatcontactwithinsolublerocksborderingthe

limestone.NosubsidencefeatureshavebeenreportedinAlaska.

PseudokarstconditionsintheUnitedStatesdevelopinareasofthick,unconsolidatedsediments

andareprimaryfeaturesinbasaltlava.Inaddition,inMississippiandAlabama.numerous

subsidencefeaturesoccurinunconsolidatedsilt,sandandgraveloftheCoastalPlain;these

subsidencefeaturesareanalogoustokarstfeatures.Thesubsidenceoccursasnumerousshallow

depressionsthataregenerallylessthan50ft(15m)deepandupto1mi(1.6km)ormorewide.

ThedepressionsoccurinMioceneandPliocenesediments800to1,000ft(240to300m)or

morethick.Oligocenecarbonaterocksarepresentbeneaththesesediments.Theoriginofthe

depressionsisnotunderstoodThedepressionsappeartobeassociatedwithpoorlydrainedareas

suchasflatlowlandsandelevated,dissected,highererosionsurfaces.Thedepressionsapparently

areconfinedtoflatsurfacesandarenotpresentonslopesthatboundtheflatsurfaces.

Excavationsinthedepressionsprobablywouldencounterweakandunstablesoilandwouldbe

subjecttoflooding.

TheHighPlainsofwesternTexasandadjacentStatescontainnumerousdepressions,someof

whichareasmuchas3mi(4.8km)longandupto1mi(1.6km)wide.Theyvaryfrom"buffalo

wallows,"3to10ft(1to3m)deep,tosteep-sidedfeaturesasmuchas250ft(75m)deep.The

depressionsarealignedalongaseriesofmajorjointsandapparentlyformedbypipingand

removaloffine-grainedmaterialalongjointplanesatdepthsgreaterthan250ft(75m).Deep

excavationsinthedepressionsencounterweak,unstablesoilsandaresubjecttofloodingfrom

groundwaterduringoccasionalperiodsofhighrainfall.

PseudokarstfeaturesinlateCenozoicbasaltlavafieldsareextensiveinsomeregionsofthewest.

ThelargestregionswiththistypeofpseudokarstareintheSnakeRiverareaofIdaho,inpartof

theColumbiaBasaltPlateauinWashingtonandOregon,andinthelavafieldsofnortheastern

California.SmallerareasareinNewMexico,Arizona,Utah,Nevada,southernCaliforniaandon

theSewardPeninsulainAlaska.Thepseudokarstfeaturesincludelavatubes,fissures,open

sinkholes,andcavesformedbyextrusionofthestill-liquidportionofthelava.Subsurface

solutionofthebedrockandsubsequentcollapsearenotinvolvedintheformationofthese

features.Lavatubes,intheformoftunnels,areupto20ft(6m)indiameter,andsomeextend

forseveralmiles.Fissuresarecommonbutseldomextendformorethan1,000ft(300m).The

fissuresandlavatubes,incontrasttosolutionfeatures,arenotingeometricalsetsbutare

generallyparallelandextendinthedirectionoftheflowofthelava.Fissuresandlavatubesare

generallynear-surfacefeatures,butsomeareasmuchas250ft(75m)deep."Sinkholes"inlava

generallylackthesymmetryofthosedevelopedinsolutionterrain.Thelavasinksarecommonly

Introduction

ThisdatasetwasconvertedfromaprintedmaptoadigitalGIScoveragetoprovideuserswitha

citablenational-scalekarstdatasettouseforgraphicanddemonstrationpurposesuntilnew,

improveddataaredeveloped.Thesedatamaybeservedontheinternetordistributedfreelywith

propercitation.BecauseithasbeenconvertedtoGISformat,thisdatacanbeeasilyprojected,

displayedandqueriedformultipleusesinGIS.Thekarstpolygonsoftheoriginalmapwere

scannedfromthestablebasenegativesoftheoriginal,vectorized,edited,andthenattributedwith

unitdescriptions.Alloftheseprocessespotentiallyintroducesmallerrorsanddistortionstothe

geography.Theoriginalmapwasproducedatascaleof1:7,500,000;thiscoverageisnotas

accurateandshouldbeusedforbroadscalepurposesonly.Itisnotintendedforanysite-specific

studies.

Thefollowingtextistakenverbatimfromtheoriginalmap,whichwasprintedfrontandbackona

singlesheet.

	

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