Earth Mat Flashcards - Ch 16

Question 1

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

Answer 1

Stress; Deformation

Question 2

The following conditions exist in uniform stress

Answer 2

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.

Question 3

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

Answer 3

3.3 km

Question 4

The following conditions exist in non-uniform stress

Answer 4

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.

Question 5

Four components of deformation

Answer 5

distortion, dilation, translation and rotation

Question 6

Homogeneous strain:

Answer 6

equal strain,
parallel lines remain parallel, perpendicular remains perpendicular

Question 7

Heterogenous strain:

Answer 7

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

Question 8

indicates a change in volume.

Answer 8

dilation

Question 9

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

Answer 9

Translation

Question 10

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.

Answer 10

Rotation

Question 11

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

Answer 11

Principal strain axes,

Question 12

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

Answer 12

σ3 , σ2 , σ1 = X, Y, Z

Question 13

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

Answer 13

Incremental strain

Question 14

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

Answer 14

X = Max
Y = Mid
Z = Min

Question 15

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

Answer 15

Coaxial strain

Question 16

Coaxial strain conditions

Answer 16

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

Question 17

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

Answer 17

Non-coaxial strain

Question 18

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

Answer 18

General shear

Question 19

Non - Coaxial strain conditions

Answer 19

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

Question 20

refers to how materials respond to stress.

Answer 20

Rheology

Question 21

Strain proportional to stress; linear relationship.

Answer 21

Hooke’s Law

Question 22

elastic behavior is also referred to as

Answer 22

Hookean behavior

Question 23

Elastic behavior can be described in terms of:

Answer 23

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

Question 24

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

Answer 24

Shear modulus

Question 25

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

Answer 25

Bulk Modulus (incompressibility)

Question 26

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

Answer 26

Poisson's Ratio

Question 27

Plastic behavior occurs through the

Answer 27

reorientation of the crystal structure

Question 28

Plastic behavior is favored by

Answer 28

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

Question 29

Mechanisms of Plastic behavior

Answer 29

Cataclastic Flow Diffusional Mass Transfer

Question 30

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

Answer 30

Cataclastic flow

Question 31

High PT; material flow through crystals

Answer 31

Diffusional Mass Transfer

Question 32

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

Answer 32

Solid State Diffusion

Question 33

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

Answer 33

Brittle behavior

Question 34

Rocks experience elastic deformation until a ________________ is attained

Answer 34

rupture point (rupture strength)

Question 35

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

Answer 35

the ultimate strength

Question 36

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

Answer 36

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

Question 37

Brittle-Ductile boundary zone at

Answer 37

~10-20 km and ~300°C

Question 38

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

Answer 38

Strain rate

Question 39

Generally, Earth materials display the following behaviors:

Answer 39

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

Question 40

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

Answer 40

250 300 400 650-700 600-800

Question 41

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

Answer 41

Competency

Question 42

commonly display ductile behavior, mohs scale less than 3

Answer 42

Incompetent

Question 43

commonly brittle ductile behavior, mohs scale more than 3

Answer 43

Competent

Question 44

refers to the amount of stress necessary to induce failure.

Answer 44

Strength

Question 45

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

Answer 45

Boudins

Question 46

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.

Answer 46

10 km

Question 47

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

Answer 47

Non - systematic

Question 48

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

Answer 48

Systematic

Question 49

Compressive vertical stress produces horizontal tensions; brittle fracturing ____________

Answer 49

forms tension veins parallel to max compression

Question 50

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

Answer 50

En echelon quartz

Question 51

Blocky/Sparry/Equant minerals indicates

Answer 51

growth within an unimpeded open space

Question 52

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

Answer 52

Fibrous veins

Question 53

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

Answer 53

Fluid pores crack a vein, seals it by precipitation

Question 54

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

Answer 54

Shear zones

Question 55

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

Answer 55

Limbs

Question 56

is a point of maximum curvature separating two limbs.

Answer 56

Hinge

Question 57

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

Answer 57

Hinge line

Question 58

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

Answer 58

Inflection point

Question 59

Elongate folds with a convex - upward structure are called

Answer 59

antiforms

Question 60

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

Answer 60

synforms

Question 61

Limbs dip toward hinge Young at hinge

Answer 61

Synclines

Question 62

Limbs dip away hinge Old at hinge

Answer 62

Anticlines

Question 63

Rock layers dip away from center Old at center

Answer 63

Domes

Question 64

Rock layers dip towards center Young at center

Answer 64

Basins

Question 65

Different folding episodes causes

Answer 65

interference patterns

Question 66

Younger folds superimposing on older folds

Answer 66

Superposed Folds

Question 67

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

Answer 67

Transposed folds

Question 68

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

Answer 68

Parasitic folds

Question 69

Characterisitcs of a parasitic fold

Answer 69

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

Question 70

fabric developed during lithification

Answer 70

Primary Fabric

Question 71

fabric; Deformation process after initial lithification

Answer 71

Tectonic Fabric

Question 72

fabric; mm scale continuous structures; no remaining undeformed parts

Answer 72

Continuous Fabric

Question 73

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

Answer 73

Spaced Fabric

Question 74

fabric; No orientation

Answer 74

Random

Question 75

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

Answer 75

Preferred Fabric

Question 76

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

Answer 76

Planar features

Question 77

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

Answer 77

Axial planar cleavage

Question 78

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

Answer 78

upright fold

Question 79

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

Answer 79

complex folding patterns occured

Question 80

form by the intersection of two planar fabrics

Answer 80

Intersection lineations

Question 81

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

Answer 81

Pencil cleavage

Question 82

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

Answer 82

Crenulation lineations

Question 83

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

Answer 83

Slip or fibre lineations

Question 84

are fibre lineations produced during displacement in faults and shear zones

Answer 84

Slickenlines