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GLE Reviews > Earth Mat Flashcards - Ch 16 > Flashcards

Earth Mat Flashcards - Ch 16

1
Q

___is a directed force of some magnitude applied over an area.
___is a change induced by stress

A

Stress; Deformation

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2
Q

The following conditions exist in uniform stress

A

The three perpendicular, principal stress axes can have any orientation as stress is equal in all directions.
No shear stresses occur.
No change in shape occurs.
Volume change can occur.

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3
Q

a 1 kbar (0.1 GPa) would correspond to what depth

A

3.3 km

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4
Q

The following conditions exist in non-uniform stress

A

Stress axes are not equal in all directions.
Shear stresses can occur on rock bodies, but not on a principal plane
Shape changes can occur.
Volume change can occur with corresponding changes in density.

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5
Q

Four components of deformation

A

distortion, dilation, translation and rotation

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6
Q

Homogeneous strain:

A

equal strain,
parallel lines remain parallel, perpendicular remains perpendicular

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7
Q

Heterogenous strain:

A

strain intensity varies,
Angular changes
Parallel or perpendicular arent the same no more :(

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8
Q

indicates a change in volume.

A

dilation

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9
Q

, also known as displacement , means that an object has moved from one point to another point.

A

Translation

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10
Q

infers that an object has moved in a circular arc about an axis, sort of like tightening a screw into a wall or the way in which a wheel rotates around an axle.

A

Rotation

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11
Q

like stress axes, are imaginary lines that are perpendicular to each and intersect planes of zero-shear strain

A

Principal strain axes,

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12
Q

How would stress axes and pricipal strain axes correspond to each other

A

σ3 , σ2 , σ1 = X, Y, Z

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13
Q

refers to one or more intermediate strain steps describing separate strain conditions

A

Incremental strain

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14
Q

Strain axes are denoted by the letters X, Y and Z as follows:

A

X = Max
Y = Mid
Z = Min

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15
Q

implies that no rotation of the incremental strain axes occurred from an initial to final strain state.

A

Coaxial strain

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16
Q

Coaxial strain conditions

A

Pure shear (irrotational strain)
Requires conditions such as
Uniform elongation at a single reaction
Uniform contraction in a perpendicular direction
Strain = stress
No volume change

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17
Q

is a rotational strain in which the strain axes rotate through time

A

Non-coaxial strain

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18
Q

Pure shear and simple shear are two idealized end members. ____________ is a combination of 2 shears; the most common one in the field

A

General shear

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19
Q

Non - Coaxial strain conditions

A

principal strain axes do not remain the same.
Simple Shear (rotational shear)
Requires conditions such as
Strain axes do not remain parallel
All strain axes rotate
Maximum elongation not parallel to direction of min compressive stress; same goes with minimum elongation, max compressive stress

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20
Q

refers to how materials respond to stress.

A

Rheology

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21
Q

Strain proportional to stress; linear relationship.

A

Hooke’s Law

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22
Q

elastic behavior is also referred to as

A

Hookean behavior

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23
Q

Elastic behavior can be described in terms of:

A

Length change (translation)
Shape change (Strain/Distortion)
Volume Change (Dilation)

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24
Q

Measure of resistance to shape change
AKA rigidity (G)
Ratio of shear stress to shear strain

A

Shear modulus

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25
Q

Resistance to a change in shape
Expressed as K = change in pressure/change in volume

A

Bulk Modulus (incompressibility)

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26
Q

Measure of fattening compared to lengthening
Response to compression
All earth materials increase in diameter, decrease in length

A

Poisson’s Ratio

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27
Q

Plastic behavior occurs through the

A

reorientation of the crystal structure

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28
Q

Plastic behavior is favored by

A

Favored by high T, high P, and low strain rate

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29
Q

Mechanisms of Plastic behavior

A

Cataclastic Flow
Diffusional Mass Transfer

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30
Q

Mesoscopic ductility facilitated by microscopic fracturing and frictional sliding
Low lithostatic pressure

A

Cataclastic flow

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31
Q

High PT; material flow through crystals

A

Diffusional Mass Transfer

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32
Q

Grain boundary or volume diffusion
High PT, translation w/in a mineral
Crystal lattice vacancies migrate to the greatest stress
Atoms relocate to minimal stress

A

Solid State Diffusion

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33
Q

is permanent, irreversible deformation characterized by the development of visible fractures and loss of cohesion between rock particles.

A

Brittle behavior

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34
Q

Rocks experience elastic deformation until a ________________ is attained

A

rupture point (rupture strength)

35
Q

the material is the maximum stress level that can be achieved prior to the onset of brittle failure.

A

the ultimate strength

36
Q

is the depth within Earth where rock behavior changes from brittle to ductile behavior

A

The brittle-ductile boundary (or brittle-ductile transition)

37
Q

Brittle-Ductile boundary zone at

A

~10-20 km and ~300°C

38
Q

refers to the rate at which rock is pulled apart, compressed, or sheared

A

Strain rate

39
Q

Generally, Earth materials display the following behaviors:

A

Brittle behavior: shallow depth, low T, high strain rate
Ductile behavior: deeper depth, high T, low strain rate

40
Q

temperatures at which change from brittle to ductile behavior.
(Bt, Qtz, Felds, Amp, Gar)

A

250
300
400
650-700
600-800

41
Q

is a term that describes the resistance of rocks to flow. Rocks that Flow easily are less competent, or incompetent

A

Competency

42
Q

commonly display ductile behavior, mohs scale less than 3

A

Incompetent

43
Q

commonly brittle ductile behavior, mohs scale more than 3

A

Competent

44
Q

refers to the amount of stress necessary to induce failure.

A

Strength

45
Q

are isolated remnants of competent rock that once formed a continuous bed surrounded by less competent rocks; formed by rupture

A

Boudins

46
Q

Brittle behavior commonly occurs at depths less than _________ because of upper crustal low temperature/low lithostatic pressure conditions, which allows for the development of fractures.

A

10 km

47
Q

_______vein arrays are produced by high strain rate events that blast rock apart due to high pressures.

A

Non - systematic

48
Q

__________ vein arrays consist of veins that display orientations suggesting a common origin in response to directed stress.

A

Systematic

49
Q

Compressive vertical stress produces horizontal tensions; brittle fracturing ____________

A

forms tension veins parallel to max compression

50
Q

vein array consists of a series of offset, parallel veins that formed in response to sinistral shear

A

En echelon quartz

51
Q

Blocky/Sparry/Equant minerals indicates

A

growth within an unimpeded open space

52
Q

displays a linear, acicular character, vein growth was incremental in response to fracture width increases.

A

Fibrous veins

53
Q

Fibrous veins develops by a repearted cycle of crack and seal mechanism. Explain the process

A

Fluid pores crack a vein, seals it by precipitation

54
Q

are essentially ductile faults in which displacement is dominated by plastic deformation processes rather than brittle rupture

A

Shear zones

55
Q

are relatively straight (low curvature) layers separated by a high curvature region of the hinge

A

Limbs

56
Q

is a point of maximum curvature separating two limbs.

A

Hinge

57
Q

is an imaginary line connecting a series of hinge points along the strike of the fold

A

Hinge line

58
Q

is the point at which the sense of curvature changes from one fold to another.

A

Inflection point

59
Q

Elongate folds with a convex - upward structure are called

A

antiforms

60
Q

Elongate folds with a concave - upward shapes are referred to as synforms.

A

synforms

61
Q

Limbs dip toward hinge
Young at hinge

A

Synclines

62
Q

Limbs dip away hinge
Old at hinge

A

Anticlines

63
Q

Rock layers dip away from center
Old at center

A

Domes

64
Q

Rock layers dip towards center
Young at center

A

Basins

65
Q

Different folding episodes causes

A

interference patterns

66
Q

Younger folds superimposing on older folds

A

Superposed Folds

67
Q

consist of folds in which the limbs and hinges have been pulled apart due to extension
Occur with multiple fold generations; involves replacement of ealier tectonic fabric by a recent ductility

A

Transposed folds

68
Q

are small folds occurring in the limbs and hinges of larger scale folds.

A

Parasitic folds

69
Q

Characterisitcs of a parasitic fold

A

Upper bed displaces toward hinge, lower bed away hinge
Right rotation produces z-shape clockwise rotation
Left rotation produces s-shape counterclockwise rotation
Minimal rotation at hinge

70
Q

fabric developed during lithification

A

Primary Fabric

71
Q

fabric; Deformation process after initial lithification

A

Tectonic Fabric

72
Q

fabric; mm scale continuous structures; no remaining undeformed parts

A

Continuous Fabric

73
Q

fabric; some undeformed space exists between fabrics; visible deformed and undeformed parts

A

Spaced Fabric

74
Q

fabric; No orientation

A

Random

75
Q

fabric; arrangement in a predictable manner; 2 main classes:
Folations (planar)
Lineations (linear)

A

Preferred Fabric

76
Q

are sheet - like structures that include joints, veins, faults, axial surfaces of folds, shear zones and cleavage.

A

Planar features

77
Q

Parallel folations near perpendicular to maximum compressive stress; converges towards inner arc of hinge

A

Axial planar cleavage

78
Q

Where S1 = Axial plane cleavage and S0 = Bedding angle
S1 > S0 would be

A

upright fold

79
Q

Where S1 = Axial plane cleavage and S0 = Bedding angle
S1 < S0 would imply

A

complex folding patterns occured

80
Q

form by the intersection of two planar fabrics

A

Intersection lineations

81
Q

is an intersection lineation marked by the development of elongate, pencil - like shards

A

Pencil cleavage

82
Q

are linear features that occur as a result of a secondary cleavage imposed upon a fine - grained rock (slate or phyllite) that experienced an earlier cleavage

A

Crenulation lineations

83
Q

refer to vein mineral fibers that precipitate on rock surfaces via crack – seal processes

A

Slip or fibre lineations

84
Q

are fibre lineations produced during displacement in faults and shear zones

A

Slickenlines

GLE Reviews (11 decks)

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