Crustal Deformation Flashcards
Deformed (strained) rocks show…
tilted beds, metamorphic alteration, folding, and faulting, UNLIKE Undeformed rocks.
Deformation can be classified as 3 types:
- Displacement
- Rotation
- Distortion
Displacement is…
A change in location
Rotation is…
A change in spatial orientation
Distortion is…
A change in shape
Strain vs. Stress
Strain: 1. Stretching 2. Shortening 3. Shearing
Stress: 1. Tension 2. Compression 3. Shearing 4. Pressure
What are the two behaviors when discussing deformation?
Brittle vs. Ductile
occurs in the shallower crust, rocks break by fracturing
Brittle Deformation
occurs at higher P and T conditions, which causes rock to deform by flowing and folding
Ductile Deformation - occurs at greater depth
3 types of Dip Slips
Normal Faults, Reverse Faults and Thrust Faults (below 35 degrees)
Strike-slip faults
- move sideways past each other
Left Lateral movements
the opposite block moves to the left
Right Lateral movements
The opposite block moves to the right
What is the dominant cause of earthquakes?
Sudden movement at faults
a line along which curvature is greatest
A hinge
Limbs
are the less curved “sides” of a fold
connects hinges of successive layers
Axial plane
Anticline
a fold that looks like an arch.
a fold that opens upward like a trough
syncline
A nonplunging fold
has a horizontal hinge
A plunging fold
has a tilted hinge
a fold with the appearance of an
overturned bowl. Exposes older rocks in
the center.
A dome
A basin
a fold shaped like an upright bowl. A basin exposes younger rocks in the center.
planar rock fractures without any offset that develop from tensile stress in brittle rock.
Joints
Viens are
Fractures filled with minerals
What are the four causes of mountain building?
- Continental collision
- Convergent boundaries
- Continental rifting
- Delamination
What is Isostasy?
Surface elevation is a balance between forces of gravitational attraction (which pulls plates into the mantle) and buoyancy (which floats lithosphere on top of the mantle)
Off-scraped sediment
Accretionary prisms
removal of deep lithospheric mantle can cause uplift
Delamination
Ductile rock eventually flows out from beneath high mountains, which then settle downward like soft cheese. The upper brittle crust breaks into faults. This process, which leads to destruction of the mountains, is known as
orogenic collapse
What is a craton?
continental crust that hasn’t been deformed in 1 Ga
There are two cratonic provinces:
Shields and Platforms
