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DEFORMATION OF THE EARTHS CRUST • Types of Deformation 1. folds 2. faults. Deformation. 1. Elastic – nonpermanent, rock returns to original shape 2. Ductile – permanent, rock flows or bends 3. Brittle – permanent, rock breaks. Rheology. Stress vs. Strain. Force. Deformation.
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DEFORMATION OF THE EARTHS CRUST • Types of Deformation 1. folds 2. faults
Deformation 1. Elastic – nonpermanent, rock returns to original shape 2. Ductile – permanent, rock flows or bends 3. Brittle – permanent, rock breaks
Rheology Stress vs. Strain Force Deformation
Ductile Brittle
How Rocks Become Deformed 1. compression forces 2. tensional forces 3. shearing forces
Rheology Stress vs. Strain Force Deformation
Rheology Stress vs. Strain Force Deformation
Folded Rocks 1. due to compressional forces 2. types of folds i. monocline ii. anticlines iii. synclines
Monocline, WY George Davis
Folded Rocks 3. anatomy of a fold i. limbs ii. axial plane iii. plunge
Folded Rocks 2. types of folds iv. overturned v. asymmetrical
Anticline Axial plane Bill Evarts Fig. 10.11
Asymmetric Folds Breck Kent
Overturned Folds Fig. 10.1 Phil Dombrowski
Folded Rocks 2. types of folds vi. domes vii. basins
Folded Rocks 2. effects of folds i. mountain building (orogenies)
Fractured Rocks 1. How a rock breaks i. joints
Fractured Rocks 1. How a rock breaks i. joints ii. faults
Anatomy of a fault i. head wall (or hanging wall) ii. foot wall iii. fault plane
Anatomy of a fault iv. strike & dip
Types of Faults • Strike-slip faults have movement that is predominantly horizontal and parallel to the strike of the fault plane • A viewer looking across to the other side of a right-lateral strike-slip fault would observe it to be offset to their right • A viewer looking across to the other side of a left-lateral strike-slip fault would observe it to be offset to their left • Oblique-slipfaults have movement that with components parallel to both the strike and dip of the fault plane Right-lateral San Andreas Fault
Effects of faulting i. horsts and grabbens Horst Graben Horst