crustal deformation. types of deformation folds faults & joints

Crustal Deformation

Crustal DeformationTypes of DeformationFoldsFaults & Joints

TermsDip angleAngle of tilt away from horizontal

Types of DeformationGEOL131: Crustal Deformation

ElasticRock bends but snaps back to original shapeEarthquakes

Elastic limitCapacity of rock for elastic deformation

If elastic limit exceeded, deformation is permanent

GEOL131: Crustal Deformation: Types of Deformation

BrittleRock breaks

Colder, harder, and shallower rock tends to be brittle

GEOL131: Crustal Deformation: Types of Deformation

DuctileRock bends permanently

Deeper, hotter, weaker rock tends to be ductile

GEOL131: Crustal Deformation: Types of Deformation

FoldsGEOL131: Crustal Deformation

Folded RocksProduct of ductile deformation

Form at deep crustal levelsRock is warmer

GEOL131: Crustal Deformation

Basic Fold AnatomyGEOL131: Crustal Deformation: FoldsAxisLimbLimb

Anticlines & SynclinesGEOL131: Crustal Deformation: Folds

DomesGEOL131: Crustal Deformation: Folds

BasinsGEOL131: Crustal Deformation: Folds

MonoclinesGEOL131: Crustal Deformation: Folds

Fold OrientationsGEOL131: Crustal Deformation: FoldsSymmetricalBoth limbs have same dip angle

AsymmetricalLimbs have different dip angles

Fold OrientationsGEOL131: Crustal Deformation: FoldsOverturnedOne limb tilted more than 90 degrees

RecumbentBoth limbs horizontal

Fold OrientationsGEOL131: Crustal Deformation: Folds

UprightFold axis not tilted

PlungingFold axis is tilted

Recognizing folds in map viewGEOL131: Crustal Deformation: Folds

What patterns do folds make on the Earths surface?

There is usually no cross-section view available to geologists

Recognizing folds in map viewGEOL131: Crustal Deformation: FoldsUpright anticline

Upright syncline

Oldest layerYoungest layer

Recognizing folds in map viewGEOL131: Crustal Deformation: FoldsUpright anticline

Upright syncline

Oldest layer at centerYoungest layer at center

Recognizing folds in map viewGEOL131: Crustal Deformation: FoldsArrows show direction of fold axis tiltOldest layer at centerYoungest layer at center

Recognizing folds in map viewGEOL131: Crustal Deformation: FoldsDome: oldest layer at centerBasin: youngest layer at center

Faults & JointsGEOL131: Crustal Deformation

Basic Fault AnatomyGEOL131: Crustal Deformation: Faults & JointsHanging WallFootwall

Normal faultsReverse faultsThrust faultsDip-Slip FaultsGEOL131: Crustal Deformation: Faults & Joints

Dip-Slip Faults: NormalGEOL131: Crustal Deformation: Faults & Joints

Dip-Slip Faults: ReverseGEOL131: Crustal Deformation: Faults & Joints

Dip-Slip Faults: ThrustGEOL131: Crustal Deformation: Faults & Joints

Normal faultsTensional stressHanging wall moves downReverse faultsCompressional stressHanging wall moves upThrust faultsCompressional stressFootwall moves upLower angle than reverse faultsDip-Slip Faults: SummaryGEOL131: Crustal Deformation: Faults & Joints

Left-lateralRight-lateralCaused by shear stressStrike-Slip FaultsGEOL131: Crustal Deformation: Faults & Joints

Strike-Slip FaultsGEOL131: Crustal Deformation: Faults & Joints(Right-lateral)

JointsFractures with no movement

Cause accelerated weatheringGEOL131: Crustal Deformation: Faults & JointsWeathered joints in southern Utah

Mountain BuildingGEOL131: Crustal Deformation

Types of Tectonic Mountain Building

Subduction zone

Continental collision

Fault-block mountains

GEOL131: Crustal Deformation: Mountain Building

New TermGEOL131: Crustal Deformation: Mountain BuildingACCRETIONARY WEDGE: Sediment & rock scraped off subducting plate onto overriding plate

Mountains Built at Subduction Zones

Volcanic arc

Uplifted accretionary wedge

Uplifted igneous intrusions

Accreted volcanic island arc

GEOL131: Crustal Deformation: Mountain Building

Mountains Built at Subduction Zones: Volcanic arcGEOL131: Crustal Deformation: Mountain Building

Mountains Built at Subduction Zones: Uplifted accretionary wedgeGEOL131: Crustal Deformation: Mountain Building

Mountains Built at Subduction Zones: Uplifted accretionary wedgeGEOL131: Crustal Deformation: Mountain Building

Mountains Built at Subduction Zones: Uplifted igneous intrusionsGEOL131: Crustal Deformation: Mountain Building

Mountains Built at Subduction Zones: Accreted Volcanic Island ArcGEOL131: Crustal Deformation: Mountain Building

Mountains Built by Continental CollisionsGEOL131: Crustal Deformation: Mountain Building

Mountains Built by Continental CollisionsGEOL131: Crustal Deformation: Mountain BuildingContinental escape: blocks of continental crust are pushed away from a continental collision zone

Mountains Built by Continental CollisionsCompressional stress

Folding

Reverse and thrust faultingGEOL131: Crustal Deformation: Mountain Building

Fault Block MountainsTensional stress

Normal faultingGEOL131: Crustal Deformation: Mountain Building

Fault Block MountainsGEOL131: Crustal Deformation: Mountain BuildingGrand Tetons

End of Chapter