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1、VolcanicLandformsPaulaMessinaVolcanicContributionstoLandscapeDevelopmentnConstructiveProcesses–volcaniceruptionsnErosionalProcesses–intrusivelandformsVolcanoTypes:ShieldVolcanoesnFluid,basalticlavanMaunaLoa:10,000m(33,000ft.)frombase1VolcanoTypes:CompositeC
2、onesnIntermittentlava/pyroclasticsnPasty,andesiticlavaproducessteeperslopesthanshieldvolcanoesnSomebasalts,Mt.Shasta(inthedistance),NorthernCaliforniarhyolitesVolcanoTypes:PlugDomesnRhyolitic,daciticlava–“thicktoothpaste”nIrregularsummitsurfacenExamples:Sho
3、waSin-Zanplugdome,JapanMonoCratersVolcanoTypes:SpatterConesnBlobsofairbornelavanFoundaroundsmallvents2VolcanoTypes:CinderConesn25o-30oslopesnLoosepyroclasticsParicutRn,1943areincapableofwithstandingfluidpressureinthevent(solavamayflowfromthebase)SPCrater,Ar
4、izonaVolcanoTypes:TableMountainsnSub-glacialeruptionsHerdubreid,IcelandCratersandCalderasnCrater:diameter.100s-1000smetersnCaldera:diameter.1-10skilometers“Crater”Lake'swatersfillacalderaninekilometersindiameter,whoseflooris600metersbelowthelakelevel3Calder
5、asformedbyExplosions(1):Santorinin1620B.C.Santorini,Greeceexplosionformeda10km.calderaCalderasformedbyExplosions(2):Yellowstonen2.0,1.3,and0.6MYAnYoungestcaldera:80kilometerslong,50kilometerswidenRhyoliticmagma(a.k.a.yellowstone)CalderasasCollapseStructures
6、:LongValleynFormedafterthe700,000yBPeruption1978-1994seismicity4CalderasasSubsidenceFeaturesnFlankeruptionsemptythemagmachamberbelowthesummitKilaueaCaldera:Halema’uma’uLavaFlows(1):PahoehoenFluidnBasalticnRopynHummockyLavaFlows(2):A’anMoreviscousthanpahoeho
7、enLessdissolvedgasnMayformthetoeofapahoehoeflowAccretionarylavaballs5LavaFlows(3):LavaTubesnFormwithinfluidlavaflowsnCommoninpahoehoenMayformcollapsestructuresThurstonLavaTube,HawaiiLavaFlows(4):OtherSurfaceFeaturesnPressureRidges–Orthogonaltothedirectionof
8、flow–Convexdownslope–~1mhigh,30-50mlongPressureRidgesnLavaLeveesnSqueeze-UpsnTreeMoldsVolcanicRiftZonesnElongatecracks–localizedtension(particularlyinbasalt)–large-areacrustalactivityEastAfricanRiftSys
