Test 1

Question 1

Primary Structures

Answer 1

Develop during formation of the rock body

Question 2

example of primary structures

Answer 2

cross bedding, ripples, mud cracks

Question 3

Secondary Structures

Answer 3

Form as a result of deformation after rocks formed

Question 4

What are joints?

Answer 4

Tensile fractures with little displacement

Question 5

How do joints form?

Answer 5

Joints arise from brittle fracture of a rock or layer due to tensile stress.

Question 6

trend?

Answer 6

the orientation of a linear feature

Question 7

plunge?

Answer 7

the angle from horizontal of a linear feature

Question 8

rake?

Answer 8

the angle to a linear featured measured from the strike line of a plane

Question 9

vein?

Answer 9

fractures filled with minerals that crystallized/precipitated from fluids flowing through rock

Question 10

fault?

Answer 10

shear fractures that have accommodated notable displacement

Question 11

folds?

Answer 11

systematically curved layers

Question 12

Cleavage?

Answer 12

closely spaced surfaces that give

a ‘woody’ appearance

Question 13

foliation?

Answer 13

Layering produced by ductile deformation

Question 14

lineations

Answer 14

elongate linear features

Question 15

shear zones

Answer 15

deformation distributed over a thickness of

rock (meters to kilometers)

Question 16

most common joint arrays/sets

Answer 16

orthogonal (90 degree angles)

Question 17

plumose structure?

Answer 17

similar to a feather, shows joint propagation direction

Question 18

hackle lines?

Answer 18

accentuate plumose structure, like individual fibers of feather

Question 19

arrest lines?

Answer 19

look like ovals in plumose structure

Question 20

griffith crack theory

Answer 20

pre-existing microcracks in a rock act as stress “concentrators”, largest properly oriented Griffith Cracks
(i.e., perpendicular to tensile direction)
propagate to form a through-going crack

Question 21

what can produce cracks?

Answer 21

thermal contraction, outer arc extension, removal of overburden (unloading), exfoliation joints (pluton)

Question 22

why are joints in uppermost crust (few km)?

Answer 22

Stresses become more compressive with depth to the

point where rocks can’t “pull-apart”

Question 23

rock strength, depth and temp relationship

Answer 23

strength increases with depth until temps raise to the point where strength begins to decrease.

Question 24

shear fracture?

Answer 24

Fractures with a component of “sliding” motion

due to compression, most common

Question 25

shear fracture angle

Answer 25

roughly 30 from sigma 1

Question 26

normal fault dip angle

Answer 26

around 60

Question 27

thrust fault dip angle

Answer 27

around 30

Question 28

Anderson Classification of Tectonic Stress Regimes?

Answer 28

On average, shear fractures form 30°

from s1 and often form as conjugate sets

Question 29

hanging wall

Answer 29

the block above the fault

hang your lantern on it

Question 30

foot wall

Answer 30

the block below the fault

stand on it

Question 31

stratigraphy?

Answer 31

the age of the rocks

Question 32

The Keys to Describing Slip Along a Fault

Answer 32

direction, sense, magnitude

Question 33

Slickenlines/Striations:

Answer 33

scratches (lineations) on a surface (slicken surface

Question 34

Mullions?

Answer 34

Linear deformation structures formed in the interface between a competent and an incompetent rock
(significant viscosity contrast)

Question 35

Chatter Marks?

Answer 35

Step-like features oriented perpendicular to striations;

give information about the sense of shear

Question 36

drag folds?

Answer 36

can be used to determine sense of a fault

Question 37

normal/extensional faults

Answer 37

Dip slip fault on which the hanging-wall
has moved down relative to the
footwall. younger on older

Question 38

scarps?

Answer 38

triangular faceted spurs due to valleys cutting through a fault scarp. wasatch front

Question 39

horst

Answer 39

high section of normal fault

Question 40

graben

Answer 40

low section of normal fault

Question 41

listric normal fault

Answer 41

bowl looking

Question 42

domino normal fault

Answer 42

domino sections tilt as extension increases

Question 43

graben vs half graben

Answer 43

graben surrounded by 2 horsts, half is on one side (listric)

Question 44

sedimentary growth strata

Answer 44

if it can be dated, great for getting at timing & rates of extension. thickens towards fault. drag folds

Question 45

rift

Answer 45

forms where the crust is pulled apart by tectonic forces.

Question 46

3 rift phases

Answer 46

Early extension, Stretching phase, Post rift subsidence and

sedimentation

Question 47

reverse faults accommodate what?

Answer 47

shortening

Question 48

what are orogenic systems/wedges like?

Answer 48

snow plow

Question 49

Two types of structural styles in thrust belts

Answer 49

thin skinned and thick skinned

Question 50

flat

Answer 50

fault remains parallel to bedding

Question 51

ramp

Answer 51

fault crosses bedding at an angle

Question 52

imbricate fans

Answer 52

blind thrust faults, new faults rotate old ones in the snowplow like effect

Question 53

duplexes

Answer 53

blind thrust faults, includes horses, 3 types.

Question 54

2 types of strike slip step overs

Answer 54

bends and oversteps

Question 55

2 directions of strike slip

Answer 55

right and left lateral

Question 56

what do strike slip fans and duplexes resemble in map view?

Answer 56

horse tails

Question 57

2 types of duplexes

Answer 57

extensional (neg flower) and contractional (pos flower)

Question 58

shear fracture

Answer 58

sigma one is at an angle to the fault

Question 59

echelon veins

Answer 59

tip points away from movement direction

Question 60

riedel shears

Answer 60

sigma one at an angle to fault, end up with extension in sigma 3