1Structure and Deformation:Folds and FaultsDeformation Terms•Stress•Strain•Compression stress•Tension stress•Shear stress•Elastic strain•Plastic strain•Ductile strain•Brittle strain•Anticline•Syncline•Monocline•Strike•Dip•Joint•Fault•Dip-slip fault•Strike-slip fault•Oblique-slip fault•Normal fault•Reverse fault•Thrust fault•Left-lateral•Right-lateralStructure and Deformation:•The driving force for geologic deformation is Earth’s internal heat engine:•Radioactive decay of U, Th, K.•The rocks get deformed because the continents move.Stress and Strain:•Stress is an applied force.•Strain is the resultant deformation.Stress is an applied force•Compressional (pushed together)•Tensional (pulled apart)•Shear (tearing)•Isostatic (hydrostatic)Strain is deformation•Elastic deformation is temporary.–Like an elastic band•Plastic deformation is permanent.–Materials that undergo continuous plastic deformation are said to be ductile.–Materials that fracture are said to be brittle.2Folds and Faults•Stress applied to rocks can result in ductile behavior (folding) or brittle behavior (faulting).•Even though rocks are usually brittle, small stresses applied over long times can result in ductile behavior.Folds•An anticline is a concave-downward fold. (arch)•A syncline is a concave-upward fold. (smile)•A monocline is a flexure.Folds in SedimentsAnticline, Split MountainSynclineMonocline3MonoclineRecumbent Fold, YukonStrike and Dip•Strike and dip are used to describe the orientation of any planar feature such as bedding in sedimentary rocks.–Strike is the compass direction of the intersection of the plane with the horizontal.–Dip is the measured angle between the plane and the horizontal.Strike and DipRock Fractures•A joint is a fracture in rock on which there has been no movement.•A fault is a fracture in rock on which there has been movement.–Dip-slip is movement in the direction of dip.–Strike-slip is movement in the direction of strike.–Oblique-slip is movement in both directions.Joints in basalt: Giant’s Causeway, Co. Antrim, Ireland4Joints in basalt: Grand CanyonFolds and FaultsDip-Slip•Dip-slip is movement of one block up or down the plane of the fault.–Normal fault: upper block moves down.–Reverse fault: upper block moves up.–Thrust fault: low angle reverse fault.FaultsStress and Fault Movement•Normal faults are tensional.•Reverse faults and thrustfaults are compressional.Strike-Slip Faults•A strike-slip fault is the horizontal movement of the blocks relative to each other.–Left-lateral: the opposite block has moved to the left.–Right-lateral: The opposite block has moved to the right.•(It doesn’t matter which block you’re on.)5San Andreas Fault(Right-Lateral)Unconformities•An unconformity is any break in the sedimentary geologic record.–A disconformity is a break with no deformation.–An angular unconformity is a break in which the lower beds have been tilted and eroded before sedimentation resumed.Angular Unconformity, GCNPDeformation Terms•Stress•Strain•Compression stress•Tension stress•Shear stress•Elastic strain•Plastic strain•Ductile strain•Brittle strain•Anticline•Syncline•Monocline•Strike•Dip•Joint•Fault•Dip-slip fault•Strike-slip fault•Oblique-slip fault•Normal fault•Reverse fault•Thrust fault•Left-lateral•Right-lateralClicker•A. Normal Fault•B. Reverse Fault•C. Thrust Fault•D. Strike-slip fault6Clicker•A. Normal Fault•B. Reverse Fault•C. Thrust Fault•D. Strike-slip fault1Clicker•A. Normal Fault•B. Reverse Fault•C. Thrust Fault•D. Strike-slip fault2Clicker•A. Normal Fault•B. Reverse Fault•C. Thrust Fault•D. Strike-slip fault3•A. Normal Fault•B. Reverse Fault•C. Thrust Fault•D. Right-lateral Strike-slip Fault•E. Left-lateral Strike-slip FaultClicker•A. Anticline•B. Syncline•C. Monocline•D. Dome•A. Angular unconfomity•B. Disconformity•C. Thrust Fault•D. Right-lateral Strike-slip Fault•E. Left-lateral Strike-slip Fault7Clicker•A. Anticline•B. Syncline•C. Monocline•D. Reverse fault1Clicker•A. Anticline•B. Syncline•C. Monocline•D. Reverse fault2Clicker•A. Anticline•B. Syncline•C. Monocline•D. Reverse
View Full Document
Unlocking...