Crustal Deformation Flashcards
Mountains manifest through three geologic processes
- Uplift
- Deformation
- Metamorphism
What is orogenesis
Building of mountains
The three results from deformation
-Displacement (change in location)
-Rotation (change in orientation)
-Distortion (change in shape)
What is strain
Change in shape caused by deformation
What are the three types of strain
-Stretching (pulling apart)
- Shear (sliding past)
-Shortening (squeezing together)
Two major types of deformation
- Brittle
- Ductile
Factors that affect the type of deformation that occurs
-Temperature
-Pressure
-Deformation rate
-Composition
What is brittle deformation
Rock breaks through fracturing and occurs in the shallow crust
What is ductile deformation
Rocks deform by flowing and folding, and occurs at higher T and P deeper in the crust
How deep into the earth’s crust do rocks transition from deforming brittlely to deforming like a ductile
~10-15 km
What is stress
A strain that is caused by force acting on a rock
What is the relationship between stress applied and the amount of deformation
Large force per area stress results in large amounts of deformation
What are the types of stress and how do they affect the thickness of the crust (3)
- Compression, causes thickening of the crust
- Tension, causes thinning of the crust
- Shear, doesn’t cause thickening or thinning
Explain what dip and strike are in terms of mapping geologic features
Strike: Horiztonal intersection with a tilted surface
Dip: The angle of the surface down from the horizontal line
What is a joint and how does it develop
Planar rock fractures without any offset, and develop from tensile stress in brittle rock
How do veins develop from joints
Joints often have cracks that allow groundwater to flow through and when minerals precipitate out its creates veins
What is a fault
A planar fracture showing displacement
Identify the difference between hanging-wall and footwall
Hanging wall is above the fault and footwall is below
What are the three classifications of faults
-Dip slip: Blocks move parallel to the dip of the fault
-Strick slip: Blocks move parallel to the fault strike plane
- Oblique slip: Components of both dip slip and strike slip
What are the three types of dip-slip faults
-Reverse fault where the hanging moves up at a steep angle
-Thrust fault where the hanging wall moves up at a gentle slope
-Normal fault where the hanging wall moves down fault slope
What is the amount of offset in a fault called
Displacement
What is an anticline
Is a fold that looks like an arch
What is a syncline
Is a fold that opens upward like a trough
What is a monocline
Is a fold-like carpet draped over a stair step
