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64 Cards in this Set
- Front
- Back
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Fabric
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Geometric configuration (orientation and distribution) of component parts at scale of hand sample or thin section
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Empirical
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An approach to to science based on observations
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Theoretical
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An approach to science derived from dynamic analysis
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Define Kinematic Strain
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Strain - change in shape of a rock results from interrelated movements of different portions with in a rock mass
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Dynamic stress
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Stress - forces that bring about changes in shape or position during deformation
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Stress
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is the intensity of force per unit area
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Define rheology
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Quantitative analysis of how rocks respond to stress
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Surface force
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Forces that act on a specific surface area in a body
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Body force
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Froces that result from action of a field at every point within the body
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Define Principal Stress
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the stresses on three (in 3-D) mutally perpendicular axes. They must be orthogonal to each other and be perpendicular to three plans that do not contain shear stresses.
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Stress ellipse/ellipsoid
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An ellipse/ellipsoid that describes the stress state at a point and enables us to determine the stress for any given plane
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Stress trajectory
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obtained by connecting the orientation of principal stress vectors at several points in a body
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Homogeneous stress
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stress that at each point in the field is the same in magnitude and orientation
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Heterogeneous stress
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Stress that is not the same in the each point in a field and/or the magnitude or orientation is not the same.
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Net displacement
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The total change from distorition, rotation, and translation
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Translation
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Movement for one place to the other
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Rigid body rotation
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Spin around an axis
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Strain
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The changes of points in a body relative to each other.
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Dilation
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Change in area or volume
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deformation path
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The path a rock takes to deform
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Stretch
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The root of quadratic elongation
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Quadratic elongation
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(The length plus the elogation)^2
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Angular shear
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The change in angle due to shear
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define shear strain
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The tangent of angular shear
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mesoscopic
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large view
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microscopic
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under a microscope view
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Flinn Diagram
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A two dimensional plot that shows three dimensional strain data
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Discuss the relationship between structural geology and tectonics
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Structual geology studies the deformation of rock, rock structures that result from deformation, and the original distruction of rock structures on earth. Tectonics is the study of how Earth is/was built. Therefore the relationship between this is symbiotic. Tectonics shows how the earth changed over the years which results in the deformations of rock or created rock structures.
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What are the challenges facing structural geologists as try to determine the processes of rock deformation, the rock structures that result, and the origin and distribution or rock structures?
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1) Historical Science : time scale and amount of physical sciences is too vast to duplicate to scale
2) Importance of scale : There is a large variety of scale (From large to microscopic) and then using the variety of scales together to map changes. 3) Importance of time: to integrate deformation over large time scales 4) Importance of 3D Visualization |
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When we go in the field, we observed the geometry of 3-D geologic structure. What do we need to determine in order to understand the evolution of that structure? What approaches might we take to study the problem?
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We need :the path the rock took to form the structure, the rates they moved over time, forces that are operated in rocks, and the rheological properties of the rocks.
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What is the difference between rheology and mechanics?
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Rheology : Quantitative analysis of how rocks respond (strain) to stress and the stress
Mechanics: How structures develop from interactions between forces and rheology |
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What can we learn from the study of rock mechanics?
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We can learn why different structures are restricted to one techtonic setting or another, why some structural patterns are repeated in other tectonic scenarios, and how much energy is require to form different collection of structures
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What is a hypothesis?
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An educated guess
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What is a scientific law?
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comes to the same result everytime. Simple true and absolute. All science would fall apart without it
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What is a scientific theory?
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An explanation of set of related observations or events based upon proven hypothesis
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How is a scientific theory established?
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Relating all the different hypothesis to a specific event
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Give the typical gradients within the earth for Pressure and Temperature
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P: 1 Kb for 3 km
T : ~25-40 C per km |
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What factors influence the rheology and mechanics of rocks? Consider both intrinsic and extrinsic factors
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minerology, cementation, porosity, grain size and shape, foliations, temperator, pressure, fluid pressure, forces applied, and time
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Why is stress a better measure of the effect of external force than force alone?
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Stress is the intensity of force per unit area, and since forces aren't even through out a rock stress is a better measurement.
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What is a stress concentration?
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An area where stress is higher than the surrounding area.
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How/why do stress concentrations occur?
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"need answers"
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What is the difference between stress and pressure?
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Stress is the measurable force inside a body and pressure is just a force.
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What are the two ways we think about stress?
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Compressional and tensional
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What are the different states of stress?
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Stress on a plane
Stress on a point |
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What are the different types of stress?
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Triaxial (all three not equal to 0)
Biaxial (two not equal to 0) Uniaxial (one not equal to 0) Genearl polyaxial (None are equal) Axial Hydrostatic (all equal) |
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What type of change, or deformation, does mean stress cause?
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A change in volume
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What type of change, or deformation, does deviatoric stress cuase?
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A change in shape
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How do we determine mean and deviatoric stress by looking at at a mohr circle?
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The mean is the center of the circle
The deviatroic stress is the point on the edge of the circle |
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How could you determine the lithostatic pressure in a region for a given depth?
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Gravity * density * Depth
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What is a stress matrix?
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Force per unit length acting on different lines (3-D planes) that are passing through a single point that have different values, but they are interrelated.
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How might stress vary with increasing pressures and temperature with depth?
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Look at strength Profiles
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We divide the total displacement field into three primary components. What are they?
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Displacement
Rigid Body Motion Strain |
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Which of the three components of the total displacement field give rise to measureable strains?
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Strain (distortion)
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What is the difference between rigid body rotation and shear strain?
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Rigid body rotation causes the distance between material objects to stay the same while the whole object rotates around a point. Shear strain causes the position of rocks to change.
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What is the 4th component of deformation?
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Dilation (change in volume)
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What is the strain ellipse?
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The Principal axis that that create a ellipse
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What does a strain ellipse shape indicate? How can we determine it's shape?
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The strain ellipse can be seen by how the axis changed from a circle to whatever shape it has become. By measuring the change in the axis's and angle you can find the new shape.
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What is finite strain?
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The measurement of strain that compares the initial and finial configuration
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What is incremental strain?
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The intermediate steps between the first and final strain.The measurement of strain that is in between final and first
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What is the difference between non-coaxial strain and coaxial strain?
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Coaxial strain is the strain in which the incremental strain axes remain parallel to the finite strain axes during progressive strain. Non-coaxial strain is strain in which the incremental strain axes rotate relative to the finite strain axes during progressive strain.
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What is the difference between pure shear and simple shear strain paths?
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Simple shear is where all material lines rotate relative to each other, principal axes do not necessaily remain the same w each increment of strain, but principal incremental strain axes rotate relative to principal axis's.
Pure shear is where the same material lines remain the principal strain axises over each incremental strain |
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What is homogeneous strain?
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Strain in which Originally straight lines remain straight, orginally parallel lines remain parallel.
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What is heterogenous strain?
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Any strain that causes straight lines to change and parellel lines to change to not parallel
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What are the different strain states?
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Simple constriction
General constriction plane strain general flattening simple flattening |
