Structural geology Flashcards by Celine Tatco

The study of the origin, geometry, and kinematics of the formation of structures.

STRUCTURAL GEOLOGY

How well did you know this?

Not at all

Perfectly

A continuous deformation that produces specific kinds of folds, ductile faults, cleavages, and foliation.

Ductile Deformation

How well did you know this?

Not at all

Perfectly

A discontinuous deformation that produces specific kinds of folds, brittle faults, and joints.

Brittle Deformation

How well did you know this?

Not at all

Perfectly

A rock mass in which the original position is questionable with respect to the adjacent terrane or continent to which it is presently attached.

Suspect Terrane

How well did you know this?

Not at all

Perfectly

Bears no resemblance to the mass to which it is attached, where the source may be the opposite side of a major
ocean.

Exotic Terrane

How well did you know this?

Not at all

Perfectly

A distinct crustal block transported by tectonic processes.

Terrane

How well did you know this?

Not at all

Perfectly

The shape of the surface topography.

Terrain

How well did you know this?

Not at all

Perfectly

The opening and closing cycle of an ocean.

Wilson Cycle

How well did you know this?

Not at all

Perfectly

A rule that states that micro- or small structures are keys to mimic the styles and orientations of macro- or larger structures of the same generation within a particular area.

Pumpelly’s Rule

How well did you know this?

Not at all

Perfectly

Structures that occur pervasively throughout the rock mass (e.g., cleavage, foliation, and certain folds).

Penetrative Structures

How well did you know this?

Not at all

Perfectly

Structures that occur as single features (e.g., a single fault or an isolated fold)

Non-penetrative Structures

How well did you know this?

Not at all

Perfectly

The state of gravitational equilibrium between Earth’s crust and mantle, such that the crust “floats” at a certain elevation that depends on factors such as thickness and density.

ISOSTASY

How well did you know this?

Not at all

Perfectly

A hypothesis, developed by John Henry Pratt, that states that the Earth’s crust has a uniform thickness below sea level with its base everywhere supporting a density at a depth of compensation.

Pratt’s Hypothesis

How well did you know this?

Not at all

Perfectly

Megascopic rock masses of the Earth’s crust with lesser density, such as mountain ranges, project higher elevations above sea level compared to those with greater density.

Pratt’s Hypothesis

How well did you know this?

Not at all

Perfectly

A hypothesis, developed by Sir George Biddell Airy, which proposes that the Earth’s crust is a more rigid shell floating on a more liquid substratum of greater density.

Airy’s Hypothesis

How well did you know this?

Not at all

Perfectly

The theory assumes that the crust has a uniform density throughout, but do not have a uniform thickness of crustal layer.

Airy’s Hypothesis

How well did you know this?

Not at all

Perfectly

The hypothesis is said to be supported by the notion that mountains resulted from the upward expansion of locally heated crustal material, which had a larger volume but a lower density after it had cooled.

Pratt’s Hypothesis

How well did you know this?

Not at all

Perfectly

Force applied to a material that tends to change the material’s dimension.

STRESS

How well did you know this?

Not at all

Perfectly

The type of stress that tends to pull a body mass apart.

Tensional Stress

How well did you know this?

Not at all

Perfectly

The type of stress that squeezes a body mass.

Compressional Stress

How well did you know this?

Not at all

Perfectly

Stress that acts perpendicular to a reference surface.

Normal Stress

How well did you know this?

Not at all

Perfectly

Stress that acts parallel to a reference surface.

Shear Stress

How well did you know this?

Not at all

Perfectly

Stress vectors oriented along the principal stress directions, defined as sigma1 > sigma2 > sigma3.

Principal Stress

How well did you know this?

Not at all

Perfectly

the non-hydrostatic stress or difference between the maximum and minimum principal stress (sigma1 > sigma2), being the diameter of the Mohr Circle.

Differential Stress

How well did you know this?

Not at all

Perfectly

also known as Deviatoric stress

Differential Stress

The force applied perpendicular to a surface of an object per unit area where the force is distributed.

Pressure

The pressure that is exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. This is a state of isotropic state of stress, where pressure is equal throughout, defined as 01 = 02 = 03.

Hydrostatic Pressure

The pressure applied by the weight of an overlying material and burial depth.

Lithostatic pressure

A component of deformation where every particle of a rock is moved in the same direction and distance, with its displacement field consisting of parallel M vectors of equal length.

Translation

A component of deformation where it is taken le as a rigid rotation that involves physical rotation of a rock bvolume relative to an external coordinate system.

Rotation

Any change in shape of the deformed rock volume

STRAIN

The difference between the position, shape and orientation of an object before and after the deformation.

Deformation

The ratio of the length of a rock mass before its deformation from its deformed state

Elongation

Stretching of a rock mass in one-dimension due to strain

Stretch

An equation associated with the Mohr Circle for strain

Quadratic Elongation

ONE-DIMENSIONAL STRAIN

Elongation , Stretch, Quadratic Elongation

TWO-DIMENSIONAL STRAIN

Angular Shear, Shear Strain

The change in angle between two originally perpendicular lines in a deformed medium.

Angular Shear

A dimensionless parameter that develops when differential movement occurs along a set of parallel lines

Shear Strain

a type of strain with three-dimensional change, where it is a ratio of values with the same units, hence, a dimensionless. Positive A represent volume gain, whereas negative A represent volume loss.

Volume Change

THREE-DIMENSIONAL STRAIN

Volume Change

A type of strain, that is a perfect coaxial deformation, that involves no internal rotation.

Pure SHear

A combination of Pure and Simple Shear.

Subsimple Shear

A combination of Simple Shear and Rigid rotation

Supersimple Shear

Deformed features in rock mass, where the original shape can be qualitatively compared to its presently deformed shape.

STRAIN MARKERS

Small, mostly sphorical features in fine grained sediments, where the red to brownish oxidized sediment has been chemically reduced to a greenish color.

Reduction spots

Among the most frequently used strain markers to indicate directions of the strain.

Pebbles

Preserved ancient lifeforms used in determining finite strain.

Fossils

Gas bubbles in volcanic rocks used in determining finite strain.

Vesicles

A graphical diagram that describes the shape of the strain ellipsoid by plotting the axial ratios X/Y and Y/Z as coordinates.

Flinn Diagram

A geometric construction for finding strain in two dimensions, typically demonstrated on fossils with orthogonal lines of symmetry in the undeformed state.

Wellman's Method

A method to determine the deformation of a rock mass that utilizes the systematic shape changes that occur in deformed ellipsoidal objects.

Rf/θ method

Uses the analysis of the distances between the centers of objects that are systematically related to the orientation of the finite strain ellipsoid.

Center-to-center Method

A simpler version of the center-to-center method, where it is done by manually tracing an overlay of coordinate origin per ellipsoid and a pair of reference axes on top of the sketch or photo of the section.

Fry Method

The study of the ability of stressed solid materials, as well as fluids and gases, to flow or deform due to strain rate, elasticity, and viscosity.

RHEOLOGY

Materials that have properties that are the same throughout any sample size.

Homogenous Materials

Materials that have properties that varies with location for either within a hand specimen, or on a regional scale, which leads to a scale- dependent rock behavior.

Heterogenous Material

Materials that have the same properties in all directions.

Isotropic Materials

Materials that have properties that vary with direction.

Anisotropic materials -

___________ are strongly anisotropic to stress, but the degree of expression of the anisotropy depends on the direction in which the stress is oriented.

Layered materials

Non-permanent or recoverable, instantaneous strain.

Elastic

Permanent or non-recoverable strain, where deformation involves breaking of atomic bonds without losing material coherency.

Plastic

Permanent strain that accumulates with time, where the strain rate-stress relationship is linear.

Viscous

The reciprocal or opposite of viscosity.

Fluidity

Elastic modulus, is an equation that measures the stiffness, or stretchability, of a material, defined as the ratio of stress (a) over strain (ε)

Young's Modulus

Rigidity modulus, is closely related to Young's modulus, is the elasticity coefficient for shearing or torsion force, being the equation that measures that rigidity of a material. Defined as the ratio of shear stress (0s) and shear strain (A):

Shear Modulus

The equation that relates the pressure change, AP, to volume change when pressure changes cause elastic deformation rather than directed force, calculating its compressibility

Bulk Modulus

An equation that expresses the relationship between volume change and stress, where the ratio of the proportional decrease in lateral measurement to the proportional increase in length in a sample material that is elastically stretched.

Poisson's Ratio

A type of rock material behavior describing the fluid-like behavior of rocks, hence, creates irreversible and permanent strain, and shows the relationship as the viscosity (1) between stress (a) and strain rate (7"), defined

VISCOUS BEHAVIOR

Stationary fluids that does not transmit shear stress.

Perfect Fluids

The ideal type of viscous behavior, described as a linear viscous behavior, where "linear" is used to emphasize a distinction from nonlinear viscous behavior, having a linearly proportional relationship between differential stress and shear strain rate.

Newtonian Fluids

BEHAVIOR A type of rock material behavior describing permanent change in shape or size of a body without fracture, accumulated over time by a sustained stress beyond the elastic limit, or yield point, of the material.

PLASTIC (SAINT-VENANT) BEHAVIOR

A perfect plastic material is one where the stress cannot rise above the yield stress and strain can continue to be accumulated forever without any change in the stress level.

PLASTIC (SAINT-VENANT) BEHAVIOR

Occurs when the rock becomes stronger or harder to deform when the stress necessary to deform the rock increases as the strain increases.

Strain hardening

Occurs when less stress is required to keep the deformation going.

Strain softening

A combination of elastic and viscous behavior where elastoviscous materials accumulate strain from the moment a stress is applied, initially behaving elastically before gradually behaving in a viscous manner.

ELASTOVISCOUS (MAXWELL) BEHAVIOR

A combination of viscous and plastic behavior where viscoplastic materials flow as perfectly viscous materials, but only above a certain yield stress, a characteristic of plastic behavior.

VISCOPLASTIC (BINGHAM) BEHAVIOR

A combination of elastic and plastic behavior where stress and elastic strain acting on a material increase until the yield point is reached, beyond which the deformation is plastic.

ELASTIC-PLASTIC (PRANDTL) BEHAVIOR