Chapter 10: Crustal Deformation and Mountain Building Flashcards
What is crustal deformation and what occurs?
All changes in the original form and/or size of a rock body.
Most crustal deformation occurs along plate margins.
(deformation may occur when stress is applied)
Factors that influence rock strength
- Temperature and confiding pressure that the rock is experiencing
- Rock type: Igneous, Sedimentary, and Metamorphic
- Time involved for deformation
A Crustal Deformation can be what?
Elastic- these are recoverable (elastic rebound theory)
Brittle- exhibit brittle failure once strength is surpassed
Ductile- solid state flow that produces a change in shape of rocks without fracturing
What is a rock fold?
Rocks bent into a series of waves
What are the two types of rock folds?
Anticline- unfolded, or arched, rock layers (looks like an ‘A’ or a rainbow)
Syncline- downfolded rock layers (looks like a ‘U’ or a ‘V’)
The rocks crust shortens and thickens due to what type of folded stress?
Compressional stress!
Anticlines and Synclines can be what?
1) Symmetrical- limbs are mirror images (boomerang)
2) Asymmetrical- limbs are NOT mirror images (check mark)
3) Overturned- one limb is tilted beyond vertical (one limb underneath another limb)
What does D.A.M.O statdnd for?
Domes
Anticlines
Middle is
Oldest
What is a dome fold?
-Circular, slightly elongated
-Upwarped displacement of rocks
-OLDEST rocks are in center of dome; exposed through weather/erosion
EX: Black Hills, South Dakota
What is a basin fold?
-Circular, slightly elongated
-Downwarped displacement of rocks
-YOUNGEST rocks are found in the center of the basin
EX: Bedrock geology of Michigan
Types of Faults
1) Dip-Slip faults
2) Strike-Slip fault
What is a Dip-Slip fault and its components?
The movement along the inclination (dip) of fault plane
Hanging wall- rock above fault surface
Footwall- rock below fault surface
Two types of Dip-Slip faults
1) Normal faults-
hanging wall block moves down.
Caused down by tensional forces
2) Reverse & Thrust faults-
hanging wall block moves up relative to the footwall
Caused by strong compressional stresses
—->
What is a Strike-Slip fault and its one type
Dominant displacement is horizontal and parallel to the trend, or strike of the fault
Transform fault-
Large strike-slip fault cuts through lithosphere
Often associated with plate boundaries
A type of rock structure that is associated with faults?
Joints- Fractures in the rock along which NO displacement (offset) has occurred.
NOT A FAULT; a crack or break in the rock due to strain
The process that collectively produce a mountain belt
Orogenesis
orogeny or mnt. building occurs at convergent boundaries
Three types of Mountain Building at Convergent boundaries
1) Andean-Type Mnt. Building
2) Continental- Continental Collision
3) Continental Accretion
What is a Continental - Continental Collision?
2 plates w/ continental crust converge and push up because neither plate is dense enough to be subducted
EX: Himalayan mountains
What is Continental Accretion?
Small crustal fragments collide w/ and are joined to continental margins
Occurred along the Pacific W. Coast
Buoyancy is the principle for what?
Isostasy
What is the process of isostatic adjustment?
The weight is removed from the crust, crustal uplifting occurs.
(the concept of floating crust that is in gravitational balance.)
Accreted crustal blocks are called?
Terranes
