Chapter 10 Crustal Deformation

Front 1

compressional stress

Back 1

Forces push a body of rock inward, resulting in compression of the body.

Front 2

tensional stress

Back 2

Forces pull a body of rock outward, resulting in elongation of the body.

Front 3

shear stress

Back 3

Opposing forces push different ends of a body of rock in opposite directions, resulting in displacement of one end of the body with respect to the other.

Front 4

Geologists use the term stress to describe forces that are applied to an area of rock. When stress is applied unequally in different directions, it is termed differential stress. Name 3 types of differential stress

Back 4

Shear stress, compressional stress, and tensional stress

Front 5

Rocks first respond to stress by deforming

Back 5

elastically

Front 6

if a rock's elastic limit is surpassed, then they will deform by two types of deformation

Back 6

ductile flow (ductile deformation) or they fracture (brittle deformation)

Front 7

Elastic deformation

Back 7

the rock will return to nearly its original size and shape when the stress is removed.

Front 8

Ductile deformation

Back 8

This is a type of solid state flow that produces a change in the size and shape of a rock body without fracturing. It occurs at depths where temperatures and confining pressures are high.

Front 9

Brittle deformation

Back 9

This involves the fracturing of rock, and is associated with rocks near the surface.

Front 10

deformations can result in the formation of several different geologic structures, such as

Back 10

Joints, faults, and folds

Front 11

Folds

Back 11

Ductile deformations where a bent rock layer or series of layers that were originally horizontal are subsequently deformed

Front 12

Faults

Back 12

Brittle deformations (fractures) in a rock mass along which movement has occurred

Front 13

Joints

Back 13

Brittle deformations (fractures) in a rock along which there has been no movement

Front 14

Compression usually results in what deformation of a geologic structure

Back 14

Folds

Front 15

Tension results in what deformation of a geologic structure

Back 15

Normal faults

Front 16

Shear stress results in what deformation of a geologic structure

Back 16

Strike-slip fault

Front 17

Name the 2 Types of folds during compresstional stress

Back 17

anticlines and synclines

Front 18

anticlines

Back 18

where the rocks create an upward arch during compresstional stress

Front 19

synclines

Back 19

where the rocks are curved downward into a trough during compresstional stress

Front 20

Large rifts or valleys, which can often have very large normal faults, are created by

Back 20

tensional forces

Front 21

Brittle deformation is dominant in the ______ crust; ductile deformation is dominant in the _______ crust

Back 21

shallow; deep

Front 22

Name 2 examples of compressional stress

Back 22

Folding and reverse faulting

Front 23

Which tectonic stress will result in a lengthening of the crust?

Back 23

tensional stress pulls things apart.

Front 24

How will a rock in the deep crust deform as a result

Back 24

distort because the rocks are at depth, the rocks will distort, but not fracture.

Front 25

a fold shaped like an upside-down U

Back 25

anticline

Front 26

a fold shaped like a right-side-up U

Back 26

syncline

Front 27

Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface

Back 27

Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface

Front 28

Imagine a syncline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface

Back 28

Rocks would be oldest on the edges and youngest in the middle

Front 29

What produces plunging folds?

Back 29

a combination of folding and tilting

Front 30

What does the term plunging fold mean?

Back 30

a fold that is tilted down into Earth

Front 31

Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging?

Back 31

Nonplunging folds look like straight lines at the surface, and plunging folds look like wavy lines.

Front 32

What is a fault?

Back 32

fractures along which rocks move

Front 33

What are rocks below and above a fault called?

Back 33

the footwall below and the hanging wall above

Front 34

Which type of force is responsible for normal fault formation?

Back 34

tensional force

Front 35

Which type of force is responsible for reverse fault formation?

Back 35

compressional force

Front 36

Which type of force is responsible for normal strike-slip formation?

Back 36

shear stress force

Front 37

Which type of fault has NO vertical motion of rocks associated with it?

Back 37

strike-slip fault

Front 38

Dip-slip faults

Back 38

faults in which the movement is parallel to the dip (or slope) of the fault

Front 39

normal faults

Back 39

dip-slip faults where the hanging wall block moves down relative to the footwall block, and they occur when the crust is extended, or lengthened.

Front 40

reverse faults

Back 40

dip-slip faults where the hanging wall block moves up relative to the footwall block, and they occur during compressive shortening of the crust

Front 41

What is rock deformation

Back 41

A general term that refers to the changes the shape or position of a rock body in response to differential stress

Front 42

What type of plate boundary is most commonly associated with compressional stress

Back 42

Convergent plate boundaries associated with mountain building

Front 43

How is strain different from stress

Back 43

Stress is the force that acts to deform rock bodies, while strain is the resulting deformation (distortion), or change in the shape of the rock body

Front 44

The major factors that influence the strength of a rock and how it will deform include

Back 44

Temperature, confining pressure, rock type, and time.

Front 45

Rock's deformation at shallow depths exhibit

Back 45

brittle fractures

Front 46

Rock's deformation at deep depths exhibit

Back 46

ductile flow

Front 47

Each strata layer in a fold is bent around an imaginary axis called what

Back 47

Hinge line

Front 48

Hinge lines that are inclined at an angle are known as the

Back 48

plunge

Front 49

A surface that connects all the hinge lines of the folded strata

Back 49

axial plane

Front 50

the axial plane divides the fold into two roughly symmetrical

Back 50

limbs

Front 51

A ________ has an essentially horizontal axial plane.

Back 51

recumbent fold

Front 52

A roughly circular upfolded structure.

Back 52

Dome

Front 53

basins

Back 53

A circular downfolded structure.

Front 54

monoclines

Back 54

Are large steplike folds in otherwise horizontal sedimentary beds. The strata are usually flat-lying or very gently dipping on both sides of the monocline.

Front 55

How is a monocline formed

Back 55

They were formed by faulting in the bedrock below

Front 56

Black hills of south dakota is a good example of what type of geologic structure

Back 56

structural dome

Front 57

Where do the youngest rocks in an eroded basin outcrop

Back 57

near the flanks

Front 58

Where do the youngest rocks in an eroded domes outcrop

Back 58

near the center

Front 59

Fault scarp

Back 59

A cliff created by movement along a fault. It represents the exposed surface of the fault prior to modification by weathering and erosion.

Front 60

Horst

Back 60

An elongate, uplifted block of crust bounded by faults.

Front 61

Grabens

Back 61

A valley formed by the downward displacement of a fault-bounded block.

Front 62

Half Grabens

Back 62

A tilted fault block in which the higher side is associated with mountainous topography and the lower side is a basin that fills with sediment.A tilted fault block in which the higher side is associated with mountainous topography and the lower side is a basin that fills with sediment.

Front 63

Detachment fault

Back 63

A nearly horizontal fault that may extend for hundreds of kilometers below the surface. Such a fault represents a boundary between rocks that exhibit ductile deformation and rocks that exhibit brittle deformation.

Front 64

thrust fault

Back 64

A low-angle or nearly horizontal reverse fault.

Front 65

Klippe

Back 65

A remnant or an outlier of a thrust sheet that was isolated by erosion.

Front 66

major strike slip faults caused by plate motion

Back 66

transform faults

Front 67

oblique-slip fault

Back 67

A fault that exhibits both dip-slip and strike-slip movement.

(angled faults that move beside each other)

Front 68

What type of faults are associated with fault-block mountains?

Back 68

normal faulting

Front 69

How are reverse faults different from thrust faults? In what ways are they the same?

Back 69

Both are brittle failure, dip-slip faults caused by lateral compression; the hangingwall block moves up and over the footwall block, and overall, horizontal distance perpendicular to the fault trace is shortened. The main distinction is based on the dip angle or inclination of the fault. Reverse faults are high-angle, dip-slip faults and thrusts are low-angle, dip-slip faults. In subhorizontal sedimentary strata, thrusts can propagate along weak bedding plane zones, resulting in extensive, horizontal displacement, crustal shortening, and emplacement of older strata over younger strata.

Front 70

describe the relative movement along a strike-slip fault

Back 70

left and right lateral movement

Front 71

outcrops

Back 71

Sites where bedrock is exposed at the surface

Front 72

What two measurements are used to establish the orientation of deformed strata

Back 72

Strike and dip

Front 73

strike

Back 73

The compass direction of the line of intersection created by a dipping bed or fault and a horizontal surface. A strike is always perpendicular to the direction of dip.

Front 74

dip

Back 74

The angle at which a rock layer or fault is inclined from the horizontal. The direction of dip is at a right angle to the strike.

Front 75

Briefly describe the method geologist use to infer the orientation of rock units that lie mainly below earth's surface

Back 75

By establishing the strike and dip of outcropping sedimentary beds and placing them on a map