Geology 131 PPT Ch10 Defomation, mountins, continents Flashcards

Terms Definitions
What is the term for any change in the shape or volume of rock layers, as a result of stress?
Deformation
What is closely related to mountain building?
Deformation
What do deformation forces at plate boundaries cause?
1. Fracturing
2. Folding
3. Metamorphism
4. Igneous Activity
5. Volcanism
Name the 2 ways rock deformation occurs?
1. Stress
2. Strain
What is the term for the force applied to abody of rock or crust?
Stress
What is the term for the change in shape that results from the applied stress?
Strain
T or F
Stress can deform or strain rocks until they become contorted or fracture
TRUE
List the 3 categories of stresses:
1. Compressional
2. Tensional
3. Shear
Name the 2 was that compressional stresses occur?
1. Faulting
2. Folding
Name the way that tensional stresses occur?
1. Faulting
Name the way that shear stresses occur?
Faulting along planes
List the types of strain?
1. compression
2. tension
3. shear
4. elastic
5. plastic
Describe compression strain:
Rock layers in compression are shortened by folding or faulting
Describe tension strain:
Lengthens the rocks or pulls them apart
Describe shear strain:
Deformation occurs along closely spaced planes like the slip between in cards in a deck
Describe elastic strain:
Rocks return to their original shape when the stress is released
Describe plastic strain:
Rocks fold or fracture when stress is applied and do not recover their original shape
T or F
Ductile rocks show a great amount of plastic strain before they fracture.
TRUE
Describe plastic strain:
BENDING before fracturing
T or F
Brittle rocks fracture after only a small amount of plastic strain.
TRUE
T or F
Inclined rocks imply they have been deformed by folding and/or fracturing.
TRUE
What are the terms for the measurements used to describe a rock body's orientation with respect to the horizontal?
Strike and dip
What is the term for the intersection of a horizontal plane with an inclined plane?
Strike
What is the term for the maximum angle of an inclined plane?
Dip
What is he term for layers of rock that have been bent or crumpled during compression (plastic strain)
Folds
What structures have ductile behavior?
Folds
Name the 3 kinds of folds:
1. monoclines
2. atniclines
3. synclines
Within the anatomy of a fold, what is the term for what divides the fold in half?
Axial plane
Within the anatomy of a fold, what is the term for each half of a fold?
Limb
Within the anatomy of a fold, what is the term for the imaginary line formed by the intersection of the axial plane and the folded beds?
Axis
What type of folds bend or flexure in otherwise horizontal or uniformly dipping rock layers where one limb is horizontal?
Monoclines
What type of folds are up-arched folds?
Anticlines
What type of folds have the oldest rocks in the cores?
Anticlines
What type of folds are down-arched folds?
Synclines
What type of folds have the youngest rocks in the core?
Synclines
Describe the 2 physical characteristics true for the upright folds in both anticlines and synclines:
Upright folds
1. axial plane is vertical
2. both limbs dip at the same angle
Describe the 2 physical characteristics true for the plungingfolds in both anticlines and synclines:
1. fold axis is not horizontal
2. axial plane may be vertical or inclined
Describe the w physical characteristics true for the upright/non-plunging folds of anticlines and synclines:
1. fold axis is horizontal
2. axial plane is vertical
What is true about inclined and overturned folds?
1. Axial plane is inclined
2. overturned folds have both limbs dipping in the sam direction
What is true about recumbent folds?
Axial plane is horizontal or nearly horizontal
What is the term for rock layers that dip away from the center, forming dome-like structures?
Domes
What is the term for rock layers that dip toward the center, form bowl shaped structures.
Basins
What is the term for fractures along which no movement has taken place?
Joints
What structures form in response to compression, tension and shearing?
Joints
What structures are fractures along which movement has taken place?
Faults
What structures' relative motion of hanging and footwall names the fault?
Faults
What lies below the fault plane?
Footwall
What is the term if the fracture is above the fault plane?
hanging wall
Name the 3 groups of faults:
1. dip-slip
2. strike-slip
3. oblique-slip
What type of faults are categorized as normal or reverse?
Dip-slip
Describe a normal fault:
1. tensional, dip-slip
2. hanging wall moves down
Describe a reverse fault:
1, compressional, dip-slip
2. hangnig wall moves up
Describe a thrust fault:
1. compressional, dip-slip
2. low angle reverse fault, less than 45 degrees
What are categories of strike-slip faults?
1. lateral
2. left lateral
What types of faults are formed by shear forces?
Strike-slip faults
What types of faults are both dip and strike movements?
Oblique-strike faults
What is the principle of Isostasy?
Isostatic rebound
What occurs when loading or unloading of the crust occurs through sedimentation, glacial activity, or erosion?
Isostatic rebound
In the principle of Isostasy, where is the crust?
The crust is floating in equilibrium on the denser mantle below.
According to the principle of Isostasy, where is the crust the thicjkest?
Beneath mountain ranges
What is the term for an episode of mountain building according to the Principle of Isostasy?
Orogeny
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