Faults, folds and regional structuresQuestionsPowerPoint PresentationSlide 4Brittle behavior of rocks: FAULTSSlide 6Anatomy of a FaultTypes of FaultsClassification of Dip-Slip FaultsNormal Faults Hanging wall moves down relative to FootwallSlide 11Reverse Faults Hanging wall moves UP relative to FootwallSlide 13Thrust FaultsLarge scale thrust FaultSmall scale thrust faultStrike-slip Faults Horizontal movement occurs along strike of fault planeSlide 18Slide 19Oblique Slip Faults Combination of stressSlide 21Tectonics and structuresSlide 23Slide 24Slide 25Slide 26Non-Tectonic forces and upliftSlide 28Slide 29Slide 30Lecture 19Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Faults, folds and Faults, folds and regional structuresregional structuresLecture #18Questions•What forces cause faults?•How do we describe the various faults?•In what plate tectonic setting do you expect to find the various types of faults?•How does fault block motion give rise to types of faults?Ductile BehaviorBrittle BehaviorBrittle behavior of rocks:FAULTS•An unfilled FRACTURE in a rock is called a JOINT–(A fracture infilled with minerals is called a VEIN)•A Fracture in which some movement or DISPLACEMENT has occurred is called a FAULT•The movement occurs along a FAULT PLANE•Faults can originate from all three types of stress:–Compressive; Tension; ShearFAULTS occurAt all scalesAnatomy of a FaultFault PlaneFault blocksStrikeDipTypes of Faults•If Fault blocks move Up or Down the Fault Plane it is a Dip-Slip Fault–Normal Faults–Reverse Faults–Thrust Faults•If Fault blocks move in the direction of the Strike, it is a Strike-Slip Fault•If there is a combination of Dip-slip and Strike-slip it is an Oblique-slip faultClassification of Dip-Slip FaultsHanging WallFoot WallStrikeFault planeNormal FaultsHanging wall moves down relative to FootwallFootwallHangingwallNormal Faults a product of TensionHWFWReverse FaultsHanging wall moves UP relative to FootwallFootwallHanging wallReverse faults a result of compressionHWFWThrust Faults•A Type of reverse fault•Low dip angle along fault planeCommon in large mountain rangesHorizontal displacement may be many tens of kilometersLarge scale thrust FaultSmall scale thrust faultStrike-slip FaultsHorizontal movement occurs along strike of fault planeLeft Lateral Right lateralSan Andreas FaultStrike of fault traceSpreading centersMid ocean ridge offset by transform (strike-slip) faultsOblique Slip FaultsCombination of stressFolds and faults can occur togetherWhat type of stress produces both Folds and FaultsTectonics and structuresNon-Tectonic forces and uplift•ISOSTASY – Less dense crust “floats” on denser mantle•Mountains have deep “roots” of lower density crust•Erosion or removal of exposed mountains causes crust to rise upward•The Modern exposure of the Appalachians may be a result of Isostatic Rebound!Lecture 19•Convergent boundariesMountains are often spectacular features that display stark evidence of the enormous forces that have folded, faulted and deformed larges areas of the Earth’s crustMountainsMount Kilimanjaro, stands by itself, rising 6000 meters above the plains of East AfricanMountainsThe American Cordillera extends all the way from South America to AlaskaMost mountain ranges on Earth are less than 100 million years old – why?Young and Old MountainsMost of the older mountain ranges are a shadow of their former selves thanks to erosion and weatheringThe Appalachian Mountains in the U.S. and the Ural Mountains in Russia are examples of very old mountain ranges, dating back hundreds of millions of yearsOld MountainsThe Himalayas are only 45 million years old and are still actively being createdYoung MountainsMountains are built at convergent plate tectonic boundariesThere are three types of convergent boundaries:Oceanic - OceanicOceanic - ContinentalContinental – ContinentalEach of these three types have certain major features in commonConvergenceConvergent subduction zones can be roughly divided into four major regions that include:Volcanic arcDeep-ocean trenchForearc regionBackarc regionSubduction ZonesWhen two oceanic plates converge, one is subducted beneath the other, causing partial melting in the mantle wedge above the plateVolcanic ArcDeep-ocean TrenchesThere are over 70,000 kilometers of deep-ocean trenches on EarthSubduction zones are quite common on EarthWhen two continental masses converge, the deep-ocean trench becomes filled with continental rockThe continental rock is less dense and more buoyantDeep-ocean TrenchesIn the forearc region, pyroclastic materials from the volcanic arc as well as sediments from the land mass collectAdditional sediments scrapped off the subducting plate are added to the forearc regionForearcAnother area where sediments and volcanic debris can accumulate is in the backarc region Here, tensional forces dominate, causing the crust to be stretched and thinnedBackarcThese tensional forces.This can create rifting and eventually lead to seafloor spreading in the backarc regionRifting in the