Faults Flashcards
Normal Fault
Extensional regime
Pulling two pieces of crust apart, plane of division is created.
FOOT WALL is higher
HANGING WALL has been pulled down
Motion of rock should be easy to tell because you can see shift/offset in layering
Reverse Faults
Compressional regime
Hanging wall moves upwards in relation to the foot wall
STEEPER ANGLE (60°) than thrust fault, therefore also less movement
Motion of rock should be easy to tell because you can see shift/offset in layering
Thrust Fault
Compressional regime
Essentially the same as a reverse fault, where the hanging wall has moved up in relation to the foot wall, however it is at a LOW ANGLE (30°)
Much more movement in the rock/hanging wall than in a regular reverse fault
Strike-slip fault
No vertical movement, its horizontal/ side to side
Horst and Graben structure
In extensional environments
Produce normal faults
Can be reactived to form reverse faults if environment because compressional
Where/why do faults occur
- When rock is COLD and snap (instead of bending/being malleable)
–> closer to surface/shallower depths within Earth’s lithosphere - Relatively low pressure
–> compressional or extensional environment - High strain rates
Where/why does folding occur
- Higher temp
–>deeper, deep crust/upper mantle/lithosphere - Higher pressure
–>compressional environment - Low strain
Foliation vs Banding
Foliation:
-Only occurs in metamorphic rocks
- Shows no difference in color becsuse minerology stays the same
-Thin layers form (looks like pages of book from the side)
Banding:
-Change in color due to chnage in mineral composition
-Can occur in all kinds of rocks
Microscopic scale deformation
Terminology
-Undulous extinction
-minerals aligned (or not) perpendicularly to main stress
Macroscropic scale deformation
Terminology
-Parasitic folds
-Rock foliation perpendicular to main stress
Regional Scale deformation
Terminology:
-Fold hinge
-Axial plane
-Anticline
-Syncline
-Antiform
-Synform
