Structural Geology Test 2

Front 1

body forces

Back 1

act on every point within a body

(GRAVITY- F=mg

Front 2

surface forces

Back 2

act of a specific surface in a body

(tectonic plates sliding past each other)

Front 3

force

Back 3

that which changes, or tends to change, body motion, a push or a pull

Front 4

lithostatic stress

Back 4

the stress at the base of a column of rock

Front 5

surface stress

Back 5

a pair of equal and opposite tractions action across a surface of specified orientation

Front 6

traction

Back 6

the measurement of force intensity

Front 7

stress

Back 7

descriptions of tractions at a given point on all possible surfaces going through a point

Front 8

What is the goal of stress analysis?

Back 8

to determine the normal and shear stresses on any plane of any orientation, given the direction and magnitude of the principal stresses

Front 9

The Mohr Circle

Back 9

a complete representation of the stress at a point. each point on the circle represents the surface stress on a different plane

Front 10

pore fluid pressure

Back 10

serves to decrease confining pressure

Front 11

effective stress

Back 11

confining pressure-fluid pressure

Front 12

differential stress

Back 12

diameter of circle

causes distortion

Front 13

mean normal stress

Back 13

center of circle

causes dilation

Front 14

deviatoric stress

Back 14

radius of circle

causes distortion

Front 15

hydrostatic

Back 15

equal stress magnitude in all directions

Front 16

Byerlee's Law

Back 16

shear stress (τ) required to slide one rock over another

Front 17

Coulomb's Law

Back 17

the straight line approximation to the shear fracture envelope

Front 18

free surface

Back 18

contact between rock and atmosphere

Front 19

Anderson's Theory of Faulting

Back 19

relationship between orientation of principle stresses and ideal fault types

Front 20

elastic

Back 20

spring like

Front 21

viscous

Back 21

like a fluid-the smallest stress will deform it

Front 22

plastic

Back 22

will not deform until yield stress is exceeded

Front 23

rheology

Back 23

the study of mechanical properties of materials

Front 24

Poisson's Ratio(v)

Back 24

degree to which a material bulges as it shortens.

Front 25

Shear modulus(mu)

Back 25

resistance to shearing

Front 26

bulk modulus(K)

Back 26

resistance to volume change (compressibility)

Front 27

Deformation is strongly dependent on:

Back 27

lithology

temperature

strain rate

fluids

Front 28

strain hardening

Back 28

a) more stress is required to maintain strain rate

b) the material gets harder to deform

Front 29

fault creep

Back 29

slow, gradual displacement(motion)

-results in small magnitude earthquakes

Front 30

stick-slip

Back 30

fault stays "locked" storing up elastic energy, then suddenly slips, releasing the stored energy

-results in large magnitude earthquakes

Front 31

strain hardening

Back 31

a) less stress is required to maintain strain rate

b) the material gets easier to deform

Front 32

kinematic analysis

Back 32

reconstruction of movements that take place during the formation and deformation of rocks at all scales

Front 33

translation

Back 33

change in position

Front 34

rotation

Back 34

change in orientation

Front 35

distortion

Back 35

change in shape

Front 36

dilation

Back 36

change in size

Front 37

pure translation

Back 37

all points more along parallel paths

Front 38

strain

Back 38

the change in size and shape that a body has experienced during deformation

-involves distortion and dilation

Front 39

homogeneous deformation

Back 39

systematic and uniform

Front 40

linear strain

Back 40

a change in length parallel to a given coordinate

Front 41

angular shear

Back 41

change in angle between two initially perpendicular lines

Front 42

state of strain

Back 42

the net result of all the deformations the body has undergone

Front 43

shear strain

Back 43

the change in angle between a radius and the tangent to the ellipse

Front 44

plane strain

Back 44

S1 is compensated by S3 so that there is no change in S2 and no change in volume

Front 45

triaxial strain

Back 45

all three axis are deformed

Front 46

uniaxial strain

Back 46

only one principle axis has been deformed

Front 47

coaxial strain

Back 47

principle finite stretching directions have the same orientation before and after deformation (pure shear)

Front 48

noncoaxial strain

Back 48

principle finite stretching axes do not remain fixed in orientation during deformation (simple shear)

Front 49

pure shear

Back 49

rock is shortened in one direction and extended in the perpendicular direction. A square becomes a rectangle

Front 50

simple shear

Back 50

rock is sheared like a deck of cards. A square becomes parallelogram

Front 51

instantaneous strain

Back 51

tiny increments of deformation

Front 52

progressive strain

Back 52

motion of an object through deformation path

Front 53

strain path

Back 53

strain states through which a body passes during progressive deformation

Front 54

strain rate

Back 54

extension(e) divided by time(t) = e/t