Structural Geology (Done) Flashcards
The study of the architecture of the rocks resulting to its deformation. It is also concerned with solids and its interaction with fluids.
Structural Geology
It deals with the forces and movements that caused the deformation.
Tectonics
A general term referring to all changes in the original orientation or form of a rock body.
Deformation
The changes in a rock that is recoverable going back to its original form once the stress is released.
Elastic Deformation
This occurs once elastic limit has surpassed and rock fractures to smaller pieces.
Brittle Deformation
This refers to objects that ruptures before any significant plastic deformation takes place.
Brittle Substances
A solid-state flow that produces a change in shape of an object without fracturing.
Ductile Deformation/ Plastic Deformation
These refer to objects that undergo plastic deformation before rupturing.
Ductile Substances
A vector quantity that changes or teds to produce changes in the section of the body defined by a magnitude and a direction.
Force
A force that causes motion
Unbalanced Force
A force that maintains equilibrium in a given body.
Balanced Force
The rate in change of velocity
Acceleration
It a type of confining pressure that increases along with depth.
Lithostatic Pressure
The mutual action and reaction of various forces exerted on a rock per unit area
Stress
This refers to forces applied is perpendicular to the area element
Normal Stress
It refers to the stress that squeezes and shortens a rock mass.
Compressive Stress
It refers that pull apart or elongates a body.
Tensile Stress
The force is tangential to the area element.
Shear Stress
The algebraic difference between the greatest stress and the least stress at a given point.
Stress Difference
The increase in confining pressure causes _______________ in volume but an increase in density.
Decrease
It is the balancing of internal forces in an area across a surface element with the material created due to deformation.
Stress
In what plane orientation if the associated stresses could either be compressive or tensile
Horizontal Plane
In what plane orientation where stresses resolved into normal or tangential components.
Inclined Plane
A unitless concept where the deformation caused by stress either changing its volume, form, or both
Strain
When _____ is exerted to the body, it exhibits inverse relationship to the body’s volume and form.
Confining Pressure
The property of a material on how it easily stretches and deforms.
Young’s Modulus/ Modulus of Elasticity
It states that the strain is proportional to stress within the elastic limit of that solid.
Hooke’s Law
The limiting factor before the object turns plastic. If value is below the elastic limit, it follows the Hooke’s Law.
Elastic Limit
A strain associated with changes in length in the direction of respective stresses.
Normal Strain
Deformation is subjected to an applied force or stresses in the same direction as its original length.
Longitudinal Strain/ Transverse Strain
The deformation where the load is applied or on the same axis as the applied load.
Lateral Strain
The strain fails through rupture.
Brittle Strain
The strain that causes changes in shape with no changes in volume.
Shear Strain
The strain with no changes in shape but has significant changes in its volume
Dilatation Strain
The displacement between individual grains caused by compression
Inter-granular Movements
The displacement within the individual crystals and slipping takes place along glide planes.
Intra-granular Movements
It states that a mineral grain possesses a greater solubility under high stress than it does under low stress.
Reicke’s Principle
The ratio between the transverse strain over axial strain; lateral strain to longitudinal strain
Poisson Ratio
The pressure that causes rupture
Strength
Rocks that are deeply buried are held together by immense pressure and tend to _________ than fractured.
Flow
The highest stress in a stress-strain curve
Ultimate Strength
A stress in a material that is able to withstand under given condition without rupturing or deforming.
Fundamental Strength
The following are factors that affect the behavior of materials:
(1) Confining Pressure
(2) Rock Type
(3) Temperature
(4) Time
(5) Viscosity
(6) Solutions
(7) Pore Pressure
(8) Anisotropy and Inhomogeneity
Relationship between Structural Geology and Geomorphology
It gives light in studying regions of recent tectonic activity and even past activities.
Relation between Structural Geology and Geochemistry
The use of chemistry in solving geology problems and it overlaps with other fields such as mineralogy, petrology, and weathering studies.
The force necessary to balance two or more forces
Equilibriant
The single force that produces the same result as two or more forces.
Resultant Forces
The process of finding the resultant of two or more forces.
Composition of Forces
The process of finding the components of a single force.
Resolution of Forces
The weight of the column of rock of a given height will be several times ________ than the weight of a column of water of the same height.
Greater
To prevent rotation and preserve equilibrium in a couple, _______ is necessary.
A second couple
Increase in Confining Pressure, Decreases the Volume of the Body, thus the Dilation is ____________.
Dilation is negative
Ductile substances may _________ rupture gigen that a longer interval of plastic deformation takes place.
Never Rupture
Most rocks are brittle under ___________
Room Temperature and Pressures
The resistance to change in shape
Rigidity Modulus
It is the 3D orientation of the fold feature.
Attitude
A trend measured on a horizontal surface. The line of interscetion between the planar feature and a horizontal plane.
Strike
The dip is measured in a vertical plane that strikes at ___________ to the strike of the bedding.
90°
The dip measured in a vertical plane not perpendicular to the strike.
Apparent Dip
The maximum angle that a geological surface declines away from a horizontal plane measured in a vertical plane that is perpendicular to the strike.
True Dip
The deviation of a plane from the vertical.
Hade
An angle a line makes with the horizontal line in that plane.
Rake
A stack of originally planar structure bent during permanent deformation which is aresult of compressional stresses thah result in the shortening and thickening of the crust.
Fold
The line of maximum curvature of a fold.
Hinge
The surface connecting all the hinges defined by its strike and dip.
Axial Plane
The line parallel to the hinges to generate a fold.
Axis
The sides of the fold extending from the axial plane to the next.
Limbs
The line along the highest part of fold or line connecting points on the same bed.
Crest
The line at the lowest part of the fold or line connecting lowest points on the same bed.
Trough
The vertical angle between horizontal plane and axis or line of maximum elongation.
Plunge
(1) Convergence of 2 Plates
(2) Intrusions
(3) Folding due to Differential Compression
~ Due to tangential compression
Causes of Folds due to Tectonic Process
(1) Cambering
(2) Valley Bulging
(3) Glacial Ice
(4) Solution
(5) Collapse Structures
~ Due to differential Compression
Causes of Folding due to Non-tectonic Processes
It happens where competent layers don’t change their thicknesses and incompetent layers are marked by cleavage sets parallel to fold axial surface.
Flexure Folding/ True Folding
This results from minute displacements along closely spaced fractures.
Shear Folding/ Slip Folding
It is similar to shear folding except slip planes are close. The deformation is analogous to lamellar flow fluids.
Flow Folding
It is a large-scale stretching, tilting or rotation of more competent blocks over less competent strata such as clays, mudstones or shales. It causes folding
Cambering
The incompetent material is forced up into a valley by the weight of the hill masses on either side.
Valley Bulging
(1) Difference in attitude at different localities
(2) Areal Map Pattern
(3) Subsurface Exploration
(4) Subsurface Studies by Geophysical Methods (Usually by Mine Studies)
The following information are used to deduce a fold.
A fold which convex upward with older rocks at the center.
Anticline
The anticlines related to extensional normal faults
Rollover Anticlines
The outcrop pattern of an anticline points to the direction of its plunge and the opposite is true for a __________.
Syncline
It concaves upwards with younger rocks the center.
Syncline
A fold where the axial surface ks vertical and upright
Symmetrical Fold
The axial surface is inclined and both limbs dip in the same direction at different angles.
Asymmetrical Fold
A fold rotated more than 90°. The normal limb is one that is right-side up.
Overturned Fold
A fold where the axial plane is horizontal.
Recumbent Fold
The curved part of the fold between normal and inverted limbs similar to a hinge.
Arch Bend
These are subsidiary recumbent anticlinal folds sticking out of the recumbent fold
Digitations
A fold where two limbs dip at equal angles in the same direction
Isoclinal Fold
These are folds where the hinges are sharp and angular.
Chevron Fold
A fold where the crest is broad and flat; hinges are present with one on both sides of the flat crest.
Box Fold
A fold where both limbs are overturned due to competent layers enclosed in a matrix of low competence.
Fan Fold/ Ptygmatic Folds
The bedding is relatively flat with a strata assuming a steeper dip. These are the result of reactivation of steep, dipping faults located in the basement rocks beneath the plateau
Monocline
A fold with one inclination with strata dip in one direction at a relatively uniform angle.
Homocline
A fold formed in an area where dipping strata locally assume a horizontal attitude.
Structural Terrace
A fold where the deformation has heen successfully intense to cause flowage.
Closed Fold/ Tight Fold
A fold where the flowage has not taken place.
Open Fold
This occurs when competent bed slides past an incompetent bed especially in overthrust blocks.
Drag Folds
These are anticlines which a mobile core has broken through the more brittle overlying rocks.
Piercing Folds/ Diapir Folds
These develop if the fold and sedimentation happened simultaneously.
Supratenuous Folds
An anticlinal uplift with no distinct trend
Basin
A synclinal depression thag has no distinct trend. A large-scale structural formation of rock strata formed by tectonic warping of previously flat-lying strata.
Basin
A fold shown in a map as a concentrically arranged contour patterns whose amplitude decreases to zero in a regular fashion in two directions
Periclinal Fold
These refer to folds that do not have any stratigraphic succession.
Antiforms/ Synforms
The axes of these folds plunge directly down to the dip of axial surface.
Reclined Folds
A major anticline composed of smaller folds
Anticlinorium
A large syncline composed of smaller folds
Synclinorium
There is an abrupt change in the fold profile when passing from one folded surface to another.
Disharmonic Folding
A sheet of sedimentary rocks where they break loose from teh underlying formation and fold independently.
Décollement
These are fractures that lack visible movement parallel to the surface plane of the structure and lack appreciable deformation.
Joints
It refers to the family of parallel, evenly-spaced joints.
Joint Set
It consists of two or more intersection joint sets
Joint System
These occur by the displacement of adjacent blocks perpendicular to the fracture plane.
Extensional Fractures
The displacement of adjacent blocks parallel to the fracture plane.
Shear Fracture
Joints arise from brittle fractures due to ___________ either imposed outside or shrinkage due to cooling of a rock body whose outside boundaries remained fixed.
(Tensile stress/ Shear Stress/ Compressive Stress)
Tensile stress
These are irregular in form, spacing, orientation that they cannot be group to distinctive joint-sets.
Non-systematic Joints
These are occurring in patterns and perpendicular to the boundaries of the rock unit.
Systematic Joint
These are roughly parallel to fold axes and fan around the fold.
Longitudinal Joints
These are approximately perpendicular to fold axes.
Cross Joints
These occur as conjugate joint sets trending oblique to fold axes; lies between the strike and the dip direction.
Diagonal Joints
It strikes parallel or essentially parallel to the strike of the bed.
Strike Joints
It strikes or essentially parallel to the direction in which the bedding, schistocity, or a structure dips.
Dip Joints
It cuts across the axial plane of a fold.
Cross-Strike Joints
It joins together at triple junctions either at or about 120˚ which is a result of cooling during basaltic flow and other extrusive and intrusive rocks.
Columnar Joints
This occurs when relative displacement of joint walls is normal to its plane due to brittle deformation in response to regional or local tectonics
Tectonic Joints
This occurs when pore fluid pressure becomes elevated as a result of vertical gravitational loading
Hydraulic Joints
It is restricted to massively exposed rock faces in a deeply eroded landscape
Exfoliation Joints
These arise near surface when bedded sedimentary rocks are brought closer during uplift and erosion
Unloading Joints/ Release Joints
These are column joints from cooling of lava or flood basalt flows
Cooling Joints
These are joints formed from pressure-solution along surfaces due to compressive stress acting across the joint.
Stylolite Joints
A planar fracture where there was a significant displacement as a result of tectonic movements.
Faults
The plane representing the fault’s fracture surface
Fault Plane
The zone of crushed rock along a single fault
Fault Zone/ Cluster of Parallel Faults
A part of the faults where it can be mapped/ seen on surface
Fault Trace/ Fault Line/ Fault Outcrop
It is the vertical displacement between Hanging Wall and Foot Wall.
Throw
The horizontal displacement between Hanging Wall and Foot Wall
Heave
It indicates the relative displacement of formerly adjacent points on opposite sides of fault.
Slip
It refers to the total displacement in the fault.
Net Slip
It is the component of net slip measured parallel to the dip of the fault.
Dip Slip
A component of net slip measured parallel to the strike of the fault.
Strike Slip
It is the component of net slip parallel to the trace of the bed.
Trace Slip
An angle a line makes with horizontal line in the fault plane.
Rake
The displacement on the opposite sides of fault and outside of the dislocated zone.
Shift
The distance between two parts of disrupted horizon measured in any direction.
Separation
The offset is horizontal with little vertical motion; parallel to fault trace.
Strike Slip Faults/ Wrench Faults/ Tear Fault/ Longitudinal Fault
It refers to faults with a left-lateral movement
Sinistral Fault
It refers to faults with a right-lateral movement
Dextral Fault
These are fault along plate boundary
Transform Fault
A fault where the offset is vertical and/or perpendicular to fault trace
Dip-Slip Faults
A low-angle normal faults with regional tectonic significance. These form a major boundary between the rocks below which exhibit ductile deformation and the top, brittle deformation.
Detachment Fault
A fault combining the dip-slip and strike-slip motions.
Oblique Slip Faults
A strike-slip fault that is parallel to the bedding.
Bedding Fault
A fault that strikes obliquely or diagonally to the strike of the adjacent rocks.
Diagonal Fault
These are short faults that overlap each other
En echelon Fault
These are circular/ arcuate faults making a circular area.
Peripheral Fault
These are parallel faults where downthrown is in the same direction
Step Fault
These are faults found within collapsed calderas.
Ring Faults
A fault where the hanging wall moves upward relative to the foot wall. These indicate compressive (horizontal) shortening of the crust.
Reverse Fault
The hanging wall moves downward relative to the foot wall. This accommodates lengthening, or extension of crust.
Normal Fault
A type of reverse fault with fault plane dipping at <45˚. It is most pronounced along convergent boundaries and associated with the formation of folds producing a mountainous geography.
Thrust Faults
A high angle fault which the relative uplifted block is the active block
Upthrust Fault
The downthrown block between 2 normal faults dipping towards each other.
Graben
The upthrown block between 2 normal faults dipping away from each other.
Gravity Fault
These are polished striated lines along the plane.
Slickensides
The rock formed from the grinding and milling when two sides of fault moving along each other (mylonites).
Fault Breccia
A tectonite with a very small grain size, unconsolidated and not cohesive.
Fault Gouge
A small step or offset on ground surface where one side of a fault has moved vertically with respect to the other
Fault Scarp
A term for the processes that produce a mountain belt.
Orogenesis
Most mountain building occurs at ___________ where _________ triggers partial melting which then provides a source of magma that intrudes the crustal rocks that form the margin of the overlying plate.
Convergent Zones; subduction
It refers to landforms where subduction beneath a continental block results on the formation of a volcanic arc along plate margins.
Andean-type Plate Margins
The accumulation of sedimentary and metamorphic rocks formed from the sediments scraped by the subducting plate plastered against the landward side of the trench.
Accretionary Wedges
It refers to any crustal fragment that has a geologic history distinct from that of the adjoin terranes.
Terranes
It is bounded by high-angle normal faults that gradually flatten with depth. These are formed in response to broad uplifting which causes elongation and faulting.
Fault-Block Mountains
It is the concept that earth’s crust is floating in gravitational balance upon the material of the mantle.
Isostasy
It refers to the process of establishing a new level of gravitational equilibrium. It allows erosion to lower the summit of mountains, the crust then rises in response to the reduced load until reaching a normal level of crustal thickness.
Isostatic Adjustment
The higher the mountain, the _______ the downward force on the rocks especially the ones at the base. This is due to erosion and mass wasting as these processes accelerate relative to elevation.
(lesser/ greater)
Greater
It is the ductile spreading at depth and normal faulting and subsidence in the upper, brittle portion of the crust. This results when the mountain starts to collapse at its own weight.
Gravitational Collapse
