Folding and faulting Flashcards
When tunnelling, which direction of the line gives the most stability? Explain why
Verticle lines give the most stability.
Horizontal lines would want to fall into the tunnel since gravity wants to compress them more.
Explain what could happen at the three plate boundaries in relation to forces.
Convergent boundary
-if brittle material, then fault
-if ductile material, then fold
Divergent boundary
-faulting occurs in both brittle and ductile material
Transform boundary
- faulting
How do you determine if a material would undergo brittle or ductile deformation?
What kind of stress is applied
-compression, tension, shear
Amount of stress
Temperature
-The higher the temperature, the more
ductile a material becomes
The strength of the material being deformed
The length of time the rock is subjected to the stress
- if pressure over a long time, then it might behave ductile
Confining pressure (depth)
-increasing confinement increases ductile behaviour
What is folding, and describe the different characteristics of it?
Folding is created by horizontal compression of ductile materials.
Anticline
-A local maximum of the fold
-The oldest rock is in the middle on an eroded plane; younger going out.
Syncline
-A local minimum of the fold
-Youngest in the middle of the eroded plane; older going out
What is recumbent folding?
Over a long period of time, folding planes become asymmetrical.
When the folding plane becomes so asymmetrical that it overlaps horizontally, a thrust fault occurs.
What are the different types of faulting?
Footwall and hanging wall
1) Normal faulting (divergent)
-Hanging wall moving down
2) Reverse faulting (compressive)
-hanging wall moving up
3)Strike-slip
-shear
-left lateral: opposite block moving left relative to the one you are standing on
-right lateral: opposite block moving right relative to the one you are standing on
faults vs joints
Faults are fractures and have observable movement.
Joints are fractures that do not have observable movements.
