Exam 1

Question 1

Force has a ____ and _____ (vector quantity)

Answer 1

magnitude and direction

Question 2

force equation

Answer 2

F = ma (newtons)

Question 3

body force

Answer 3

work at a distance and depend on amount of material (ex: gravity)

Question 4

surface force

Answer 4

works across surface of contact and depend on magnitude and area of surface

Question 5

stress is the ____

Answer 5

intensity of force

Question 6

stress on a _____ is a vector and is a ____ at a point

Answer 6

surface, tensor

Question 7

stress equation

Answer 7

stress = F/a (Pa, MPa, GPa)

Question 8

lithostatic stress

Answer 8

stress caused by the weight of the rock above a point

Question 9

uniaxial stress

Answer 9

stress state where only one of the principial stresses is nonzero

Question 10

convergent boundaries create

Answer 10

compression

Question 11

divergent boundaries create

Answer 11

tension

Question 12

transform boundaries create

Answer 12

shear

Question 13

normal stress vector is…

Answer 13

perpendicular to the surface

Question 14

shear stress vector is…

Answer 14

parallel to the surface

Question 15

in a stress ellipse the stress is acting in…

Answer 15

all directions

Question 16

stress ellipse shows…

Answer 16

the graphically the magnitude of stress

Question 17

the long axis of ellipse is…

Answer 17

max principal stress

Question 18

the short axis of ellipse is…

Answer 18

min principal stress

Question 19

sigma 2 is the…

Answer 19

the intermediate principal stress axial

Question 20

the center of a stress tensor can be considered a…

Answer 20

cube

Question 21

if the center of a stress tensor is stable then shear stress…

Answer 21

on mutually perpendicular faces are equal

Question 22

what if sigma 1 = sigma 2 = sigma 3

Answer 22

stress state is isotropic (hydrostatic stress or pressure)

Question 23

deviatoric stress and mean stress are..

Answer 23

components of total stress

Question 24

deviator stress causes…

Answer 24

permanent deformation

Question 25

simple shear

Answer 25

deformation

Question 26

pure shear

Answer 26

flattening and stretching

Question 27

sub-simple (general) shear

Answer 27

deformation by rotation and flattening and stretching

Question 28

how to measure 2D strains of a stretched pebble

Answer 28

1. calculate area of ellipse
2. find radius of circle w/ equivalent area
3. strain is calculated from difference between ellipse length axis (final) and circle radius (initial)

Question 29

rocks don’t fracture along…

Answer 29

planes of mx shear stress because internal friction

Question 30

fracture initiation in tectonic settings

Answer 30

1. increase differential stress
2. increase pore fluid pressure

Question 31

normal fault setting

Answer 31

push less from side “decrease sigma 3”

Question 32

thrust fault setting

Answer 32

push more from side “increase sigma 1”

Question 33

What causes an earthquake

Answer 33

1. fracture ruptures
2. fault develops
3. earthquake happens when fracture develops
4. when frictional limit is met stress is converted to tectonic to seismic waves and heat

Question 34

draw a normal fault and label principle stress orientations

Answer 34

YAY!

Question 35

divergent plate boundaries mean stress

Answer 35

generally lower because of principal stresses are orientated away from each other
(lower mean stress reduces the overall resistance to deformation)

Question 36

divergent plate boundaries differential stress

Answer 36

-high due to the tensional stress, causing rocks to deform more easily along fractures and faults

Question 37

convergent plate boundaries mean stress

Answer 37

-mean stress is higher due to the compression, making it more difficult for rocks to deform

Question 38

convergent plate boundaries differential stress

Answer 38

-high stress results from compression, making rocks more resistant to deformation and more likely to fold or undergo plastic deformation

Question 39

mean stress

Answer 39

represents the average or uniform stress experienced by a material in a particular direction

Question 40

differential stress

Answer 40

the difference between the maximum and minimum principal stresses in a stress field

represents the intensity of stress acting within a material and is a measure of the deformation potential or strain