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Structural Geology > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

It is the transformation from an initial to
a final geometry by means of rigid body translation, rigid body rotation, strain (distortion) and/or volume change

A

Deformation

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2
Q

This do not tell us how the
particles moved during the deformation history – they merely link the undeformed and deformed states.

the positions of points before and after deformation (can be connected with vectors.)

A

Displacement Vectors

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3
Q

moves every particle in the rock in the same direction and the same distance, and its displacement
field consists of parallel vectors of equal length.

A

Translation

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4
Q

The term refers to the distortion (strain) that is expressed in a (deformed) rock.
A change in form or shape.

A

Deformation

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5
Q

Rigid body deformation

A

Rotation and Translation

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6
Q

Non-rigid body deformation

A

Strain or Distortion

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7
Q

are the field of displacement vectors.

A

Displacements field

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8
Q

________trace the actual motion of individual particles in the deforming rock. while __________ simply connect the initial and final positions.

A

Particle path, Displacement Vector

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9
Q

The actual path that each particle follows during the deformation history.

A

Particle Path

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10
Q

referring to the progressive changes that take place during deformation

A

deformation History

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11
Q

is here taken to mean rigid rotation of the entire deformed rock volume that is being studied. It should not be confused with the rotation of the (imaginary) axes of the strain ellipse during progressive deformation.

A

Rotation

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12
Q

is non-rigid deformation and relatively simple to define:

A

Strain

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13
Q

also referred to as dilation, is commonly considered to be a special type of strain, called volumetric strain.

A

Volume Change

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14
Q

Where the deformation applied to a rock volume is identical throughout that volume, the deformation is

A

homogeneous.

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15
Q

Homogeneous: Rigid rotation and translation
Heterogeneous: Strain and volume or area change

A
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16
Q

originally straight and parallel lines will be straight and parallel also after the deformation. Further, the strain and volume/area change will be constant throughout the volume of rock under consideration.

A

homogenous deformation

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17
Q

ratio between the long and short axes of the ellipse.

A

Ellipticity

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18
Q

Homogeneous deformation can therefore be described by a set of first-order equations (three in three dimensions) or, more simply, by a transformation matrix referred to as the

A

deformation matrix

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19
Q

called the deformation matrix or the position gradient tensor, and the equation describes a linear transformation or a homogeneous deformation.

A

Matrix D

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20
Q

takes the deformed rock back to its undeformed state.

A

reciprocal or inverse deformation

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21
Q

(a single direction), strain is about stretching and shortening (negative stretching) of lines or approximately linear (straight) objects.

A

one-dimension

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22
Q

of a line is defined as e= (l-l0)/l0 where l0 and l are the lengths of the line before and after deformation.

A

Elongation

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23
Q

a line is identical to elongation (e) and is used in the analysis of extensional basins where the elongation of a horizontal line

A

Extension

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24
Q

Negative extension is called

A

Contraction

25
Q

which describes the change in angle between two originally perpendicular lines in a deformed medium.

A

Angular shear

26
Q

can be found where objects of known initial angular relations occur. Where a number of such objects occur within a homogeneously strained area, the strain ellipse can be found

A

Shear strain

27
Q

the ellipse that describes the amount of elongation in any direction in a plane of homogeneous deformation.

A

strain ellipse

28
Q

Having constant volume or area.

A

Isochoric

29
Q

An arbitrary section through a deformed rock contains a strain ellipse that is called

A

sectional strain ellipse.

30
Q

is a state of strain were stretching in X is compensated for by equal shortening in the plane orthogonal

A

Uniform Extension

31
Q

is the opposite, with shortening in a direction Z compensated for by identical stretching in all directions perpendicular to Z.

A

Uniform flattening

32
Q

where stretching in one direction is perfectly compensated by shortening in a single perpendicular direction.

A

plane strain

33
Q
  • is the deformed shape of an imaginary sphere with unit radius that is deformed along with the rock volume under consideration.
A

strain ellipsoid

34
Q

The strain ellipsoid has three mutually orthogonal planes of symmetry, the principal planes of strain, which intersect along three orthogonal axes that are referred to as the principal strain axes. Their lengths (values) are called the principal stretches.

A

important

35
Q

the eigenvectors and eigenvalues will always be identical for any given state of strain. Another way of saying the same thing is that they are

A

strain invariants

36
Q

example of strain invariants.

A

Shear strain, volumetric strain, and kinematic vorticity number (Wk)

37
Q

Any strain ellipsoid contains

A

two surfaces of no finite strain.

38
Q

For constant volume deformations

A

isochoric deformations

39
Q

The radial lines in this diagram indicate equal amounts of strain, based on the natural octahedral unit shear.

A

Hsu Diagram

40
Q

Volume and area changes do not involve any internal rotation, meaning that lines parallel to the principal strain axes have the same orientations that they had in the undeformed state. Such deformation is called

A

coaxial

41
Q

is real volume change where the object is equally shortened or extended in all directions.

A

Isotropic Volume Change

42
Q

involves not only a volume (area) change but also a change in shape because its effect on the rock is different in different directions

A

Anisotropic volume change

43
Q

implies expansion in one direction. This may occur by the formation of tensile fractures or veins or during metamorphic reactions.

A

Uniaxial extension

44
Q

where the rock shortens or extends in one direction, is another example of coaxial deformation.

A

Uniaxial strain

45
Q

implies that lines along the principal strain axes have the same orientation as they had in the undeformed state.

A

Coaxial deformation

46
Q

is a special type of constant volume plane strain deformation. There is no stretching or shortening of lines or movement of particles in the third direction.

A

Simple shear

47
Q

Between pure shear and simple shear is a spectrum of planar deformations

A

subsimple shear

48
Q

is the sum of particle paths in a deforming medium.

A

flow pattern

49
Q

Parameters that act instantaneously during the deformation history

A

flow parameters

50
Q

are the three perpendicular axes (two for plane deformations) that describe the directions of maximum and minimum stretching at any time during deformation.

A

Instantaneous Stretching Axes (ISA)

51
Q

separate different domains of particle paths.

A

flow apophyses

52
Q

describes how fast a particle rotates in a soft medium during the deformation.

A

Vorticity

53
Q

describes the velocity of the particles at any instance during the deformation history.

A

velocity field

54
Q

is a measure of the internal rotation during the deformation. The term comes from the field of fluid dynamics.

A

Vorticity

55
Q

If the flow pattern and the flow parameters remain constant throughout the deformation history, then we have

A

steady state flow

56
Q

If, on the other hand, the ISA rotates, Wk changes value or the particle paths change during the course of deformation, then we have

A

non-steady-state flow.

57
Q

which is the result of the entire deformation history.

A

Finite deformation

58
Q

which concerns only a portion of the deformation history

A

Incremental deformation

59
Q

progressive volume change

A

dilating

Structural Geology (7 decks)

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