Week 8 Flashcards
3 types of deformation
Elastic
Brittle
Ductile
Deformation
How is it going to respond: elastic brittle ductile, resulting shape
General term for the process of folding faulting shearing compression, or extension of rocks as a result of various natural forces
Ductile deformation
Folds: anticline syncline, monocline.
A type of solid state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temperatures and confining pressures are high
Brittle deformation
Deformation that involves fracturing of rock. Associated with rocks near the surface
Joint
A fracture in rock along which there has been no displacement
Hanging wall / footwall
Hanging wall: rock surface immediately above a fault.
Footwall: rock surface below a fault
Fault scarp
A cliff created by movement among a fault. Represents the exposed surface of the fault prior to modification by weathering and erosion
Faults
Normal:
Reverse
Strike slip
What is rock deformation
Changes in the shape or position of a rock body in response to differential stress
List the 3 types of differential stress/ changes they impart to rock bodies
Compressional : squeezes a rock mass- convergent
Tensional: pulls apart or elongates rock bodies- divergent
Shear: movement of one rock body past another- transform
What type of plate boundary is most commonly associated with compressional stress?
Convergent
How is strain different from stress
Strain is a change in shape caused by stress. (Resulting distortion )
How is brittle deformation different from ductile?
Brittle: stress breaks material when it exceeds the elastic limit
Ductile: flows in a solid state changes shape without fracturing
4 factors that affect rock strength
Temperature: heating makes it ductile/ malleable more brittle at low temps
Confining pressure: increases with depth, squeezes materials in all directions making them stronger and harder to break
Rock type: sedimentary is weaker
Distinguish between anticline and syncline
Anticline: compressional stress squeezes and makes arc like folds.
Syncline is opposite
How do the 3 faults differ from each other
Normal: Hanging wall block moves down relative to footwall
Reverse (thrust): hanging wall moves up.
Strike slip: parallel displacement ( moves out) right and left lateral
Sketch each type of fault and indicate stress involved and motion of hanging and footwall.
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How is a reverse fault different from a thrust fault
Thrust fault is a lower angle reverse fault
How do you figure out if a strike slip fault if right or left lateral
The side of the fault that moves as you face it
Normal fault
A fault in which the rock above the fault plane has moved down relative to the rock below
Reverse fault
Material above the fault plane moves up in relation to the material below
Strike slip fault
A fault in which movement occurs horizontally
What type of stress causes folds
Compressional
