L-Del Flashcards
Where does brittle deformation or rock failure dominate in the crust?
At shallow layers, but also been found to characterize zones in the mantle with high mechanical strength.
What is cataclasis?
Brittle deformation mechanisms, involves intrergranular deformation where the friction between the mineral grains is large enough to inhibit grain sliding, so that the grains themselves start to break.
Typical for consolidated sediments and crystalline rocks.
What is granular or particulate flow?
Brittle deformation mechanism that involves inter granular deformation where the mineral grains rotate and slide agains one another without being crushed.
Typical of unconsolidated (loose) and poorly consolidated sand at shallow burial depths.
What is frictional sliding?
Sliding or slip associated with brittle deformation is characterized by friction and is thus referred to as frictional sliding.
What is a fracture?
Surface discontinuities formed in response to external or internal stresses acting on the fractured object.
Three principal classes of fractures:
Faults, joints, veins.
What are faults?
Faults are characterized by relative movement parallel to the fracture surface.
What are joints?
Fractures with very small (commonly invisible) offset perpendicular to the fracture surface.
What are fissures?
Characterized by opening or aperture, i.e., movement normal to the fracture surface.
What are normal faults?
Dip-slip fault wit movement parallel to the dip direction. Hanging wall moves down relative to footwall, with missing section.
What are reverse faults?
Dip-slip faults with movement parallel to the dip direction. Hanging wall moves up relative to footwall, doubled section.
What is heave?
The horizontal component of the displacement.
What is throw?
The vertical component for the displacement.
What are strike-slip faults?
Movement parallel to the strike. If hanging moves right: dextral, if hanging moves left: sinistral.
What are listric faults?
Listric faults can be defined as curved normal faults in which the fault surface in concave upwards; its dip decreases with depth.
What is oblique slip fault?
Combination of dip slip and strike slip.
What are the main elements in faults?
Fault core and enveloping fault damage zone
What is the fault core?
The fault core absorbs most of the deformation and may range in width from that of a single dip surface up to several meters.
Contains various types of cataclastic material; gouge and breccias.
What is the fault damage zone?
The fault damage zone contains various types og fault-related structures, such as deformation bands and minor slip surfaces and mezo-scale shear fractures as well as joints.
Define stress.
Force per unit area.
Force that causes strain - invisible
Define strain.
Strain is the deformation that results from applied stress. Strain occurs when stress reaches a certain level.
Change in shape - visible.
Explain stress on a surface.
Stress perpendicular to a surface: normal stress (sigma_n)
Stress parallel to a surface: shear stress (sigma_s)
If a cube is oriented so that all of the shear stresses are 0, explain what you can see.
Each surface has one normal stress component, and two shear stress components.
The sides of the cube = principal planes of stress
Normal stress components = principal stress axes.
sigma_1 largest, sigma_3 smallest.
What is the mean stress?
The mean of the principal stresses.
Sigma_m =
(S_1 + S_2 + S_3)/3
Define deviatoric stress
Deviation from mean stress (avvik).
Total stress = mean + deviatoric
