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CrustalDeformationandMountainBuilding S=slide S1Everyrockbodyhasapointatwhichitwillfractureorflow Deformationreferstoallchangesintheoriginalshapeand/orsizeofarockbody S2Crustaldeformationgenerallyoccursalongplatemargins Platemotionsandtheinteractionsalongplateboundariesgenerateforcesthatcause therockstodeform S3Rockssubjectedtoforces(stresses)greaterthantheirownstrengthbeginto deformbyfracturing,folding,orflowing S4Whenstressisappliedgraduallytherocksrespondbydeformingelastically Elasticdeformation­rockreturnstonearlytheinitialsizeandshapewhentheforce isremoved­likearubberband Whentheelasticlimitisreachedtherockwillbreak(likearubberband)­brittle deformationoritwillflow­ductiledeformation S5RockDeformation Temperatureandconfiningpressure­brittledeformation­coolwithlowconfining pressure;ductiledeformation­hotwithhighconfiningpressure Rocktypemineralcompositionandtexturedeterminesifrockbreaksorflows Time­forceappliedoveraperiodoftime S6Folds Duringmountainbuildingsedimentaryandvolcanicrocks(strata)areoftenbent intofolds Foldsaretheresultofcompressionalforcesthatresultinshorteningandthickening ofthecrust Typesoffolds anticlines(antiforms) synclines(synforms) monoclines S7Thetwomostcommonfoldsareanticlinesandsynclines Anticlinesaretheupfoldingorarchingofrocklayers Synclinesarethetroughsordownfolding Thelimbofananticlineisalsothelimboftheadjacentsyncline S8Symmetricalfoldsarewhenthelimbsaremirrorimagesofeachother(leftside below) Asymmetricalfoldiswhenthelimbsarenotmirrorimages(middlebelow)

Overturned(recumbant)iswhenalimbistiltedbeyondvertical(rightbelow) S9Plungeiswhentheaxisofthefoldpenetratesintotheground Theoutcroppatternofaplunginganticlinepointsinthedirectionoftheplunge Theoutcroppatternofaplungingsynclinepointsintheoppositedirection S10Foldsareoftencoupledwithfaults Notethefracturealongtheaxisofthisfold S11Monoclinesarelarge,steplikefoldsinhorizontalstrataandappeartobethe resultofreactivationofsteeplydippingfaultzonesinthebedrockbelowthestrata Asthefaultinthebedrockmovestheductilesedimentaryfolds S12DomesandBasins Domesarebroadcircularorelongateupwardfolds(BlackHills,SouthDakota) Basinsarelargecircularorelongatedownwardfolds(Michiganhasalargebasin)­ theresultoflargeaccumulationsofsediment,whoseweightcausesthecrustto subside S13BlackHills,SouthDakota Domewithigneousandmetamorphicrockinthecenterthatiscoveredby sedimentarystrata S14Michiganbasingeologicmapshowingtheyoungestrockinthecenterwiththe ageoftherockgettingolderawayfromthecenter Theageoftherockstrataistheoppositeforadome S15Faults Faultsarefracturesinthecrustalongwhichdisplacementhasoccurred Dipslipfaults­movementalongthefaultisparalleltothedipofthefault Strikeslipfaults­movementalongthefaultishorizontalandparalleltothetrend orstrikeofthefaultsurface S16Hangingwallisthesurfaceabovethefault­overheadwherealanternmightbe hunginamine Footwallisthesurfacebelowthefault­surfacethatiswalkedoninamine S17Dipslipfaults Twomajortypesofdipslipfaultsarenormalandreverse

Normal­hangingwallmovesdownrelativetothefootwallandfaultisusuallysteep Reverseandthrust­hangingwallmovesuprelativetothefootwallandthefault canbesteep(reverse)orshallow(thrust) S18Normalfaultsaccommodatelengthening,orextension,ofthecrust Alongmidoceanridgesandareasundergoingextensionacentralblockcalleda grabendropsdownalongnormalfaultsbetweentheblocksoneithersidecalled horsts S19NormalfaultsintheBasinandRangeProvinceproducedhorstandgraben. Notethesteepnessofthefaultsnearthesurfacethatgetshallowatthebase S20Typesofforces S21Foldscomeinallsizes S22Dipslipfaults Twomajortypesofdipslipfaultsarenormalandreverse Normal­hangingwallmovesdownrelativetothefootwallandfaultisusuallysteep Reverseandthrust­hangingwallmovesuprelativetothefootwallandthefault canbesteep(reverse)orshallow(thrust) S23Normalfaultsaccommodatelengthening,orextension,ofthecrust Alongmidoceanridgesandareasundergoingextensionacentralblockcalleda grabendropsdownalongnormalfaultsbetweentheblocksoneithersidecalled horsts S24Normalfaultduetotensionalforces S25Reversefaultsarehighanglefaultswherethefootwalldropsdownrelativeto thehangingwallduetocompressionalforces S26Thrustfaultsareshallowanglereversefaultsduetocompressionalforcesonall scales­localtoregional(smalltolarge) S27Exampleofathrustfault,ChiefMountain,GlacierNationalPark,Montana S28StrikeslipFaults Displacementishorizontalandparalleltothestrikeofthefaultsurface Occuronallscales Manylargestrikeslipfaultsproduceatracethatisvisibleovergreatdistances Largefaultscanbeaseriesofparallelfaultsinazonethatmaybeseveralkmwide Crushedrockalongafaulterodeseasilyproducinglinearvalleysortroughs S29Changesintopographyassociatedwithstrikeslipfaults

S30Joints Fractureswithnoappreciabledisplacement Columnarjointingformsasigneousrockscoolandformshrinkagefractures Somefracturesassociatedwithfolding S31Thevariousterranesalongthewestcoastcanbeexplainedbyplatetectonic interactions S32VerticalMovementsoftheCrust Isostasy­floatingcrustingravitationalbalance Mountainbeltsarehigherthanthesurroundingterrainduetocrustalthickening­ rootsextenddeepintothecrust Deeperastheheightincreases Shallowerasheightdecreases S33Compressioncausesshorteningofthecrustandmountainbuilding­high mountainswithdeeproots Erosionremovesheightandrootsareuplifted S34KeyConcepts 1.Crustalandrockdeformationdefinitions 2.Typesoffoldsandforce(s)thatcreatethem 3.Typesoffaultsandforce(s)thatcreatethem 4.Howtotelldirectionofmovementonafault 5.Isostasy,theverticalmovementofthecrust:whatitisandhowitaffects mountainbuilding

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