DEFORMATION OF THE EARTHS CRUST Types of Deformation

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 Force Stress vs. Strain Deformation

Ductile Brittle

How Rocks Become Deformed 1. compression forces 2. tensional forces 3. shearing forces

Rheology Force Stress vs. Strain Deformation

Rheology Force Stress vs. Strain 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 Phil Dombrowski Fig. 10. 1

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-slip faults 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

Wildrose Graben, Southern California

NASA/TSADO/Tom Stack