Deck 7: Deformation: Modification of Rocks by Folding and Fracturing

Question 1

A fault plane strikes north-south and dips steeply to the west.Geologic observations indicate that most of the fault movement was dip-slip and that Mesozoic rocks occur east of the fault and Paleozoic rocks occur west of the fault.What type of fault is this?

A)a left-lateral fault
B)a normal fault
C)a reverse fault
D)a right-lateral fault

Answer 1

C

Question 2

The difference between a fault and a joint is that

A)faults cut through more than one layer of rock,whereas joints cut through only one layer.
B)faults cut through bedrock,whereas joints cut only the upper sedimentary layers.
C)rocks on either side of a fault have moved,whereas rocks on either side of a joint have remained stationary.
D)faults form straight lines in map view,whereas joints form zigzag lines.

Answer 2

C

Question 3

The San Andreas fault is an example of a ______ fault.

A)normal
B)reverse
C)right-lateral strike-slip
D)left-lateral strike-slip

Answer 3

C

Question 4

Which of the following is not a dip-slip fault?

A)a normal fault
B)a reverse fault
C)a right-lateral fault
D)a thrust fault

Question 5

Which of the following deformation textures forms deep in Earth's crust?

A)cataclastic textures
B)fault breccias
C)joints
D)mylonites

Question 6

What is the scientific term for a crack along which no appreciable movement has occurred?

A)axis
B)fault
C)fold
D)joint

Question 7

The San Andreas fault is a result of what type of forces?

A)compressive forces
B)tensional forces
C)shearing forces
D)all of the above

Question 8

The line formed by the intersection of an inclined sedimentary layer and a horizontal plane is called the

A)bed.
B)dip.
C)fold axis.
D)strike.

Question 9

What type of material undergoes smooth,continuous plastic deformation?

A)brittle
B)cataclastic
C)ductile
D)all of the above

Question 10

Which of the following statements about rock deformation is false?

A)Deep crustal rocks are more likely to deform ductilely than shallow crustal rocks.
B)Hotter rocks are more likely to deform ductilely than cooler rocks.
C)Most sedimentary rocks are more deformable than igneous rocks.
D)Rocks under low surrounding pressure are more likely to deform ductilely than rocks under high surrounding pressure.

Question 11

Which of the following types of tectonic forces tends to push two sides of a body in opposite directions so that they slide horizontally past each other?

A)compressive forces
B)tensional forces
C)shearing forces
D)torsional forces

Question 12

Reverse faults form in response to ______ forces.

A)compressive
B)shearing
C)tensional
D)torsional

Question 13

Which of the following conditions of natural deformation is the most difficult to simulate in a laboratory experiment?

A)the duration of the deformation event
B)the pressure during the deformation event
C)the temperature during the deformation event
D)the type of rock that was deformed

Question 14

If a basalt unit near the surface of Earth underwent compressive deformation,the result would most likely be

A)folding.
B)folding followed by faulting.
C)faulting.
D)faulting followed by folding.

Question 15

What type of fault is characterized by the rocks above the fault plane moving downward,relative to the rocks below the fault plane?

A)a normal fault
B)a reverse fault
C)a strike-slip fault
D)all of the above

Question 16

A sample of marble has deformed brittlely during a laboratory experiment.If we wish our next sample of marble to deform plastically rather than brittlely,we should conduct the next experiment at

A)lower temperature and lower confining pressure.
B)lower temperature and higher confining pressure.
C)higher temperature and lower confining pressure.
D)higher temperature and higher confining pressure.

Question 17

Which of the following types of tectonic forces tends to squeeze and shorten a rock body?

A)compressive forces
B)tensional forces
C)shearing forces
D)all of the above

Question 18

The dip of a unit represents the

A)angle at which the bed inclines from the horizontal.
B)direction of intersection of the rock layer and a horizontal surface.
C)part of the unit that has been eroded.
D)tilt of the rock unit before deformation.

Question 19

What determines whether a rock deforms in a brittle fashion versus a ductile fashion?

A)temperature
B)rock type
C)rate of deformation
D)all of the above

Question 20

What types of forces dominate at convergent plate margins?

A)compressive forces
B)tensional forces
C)shearing forces
D)torsional forces

Question 21

What two measurements describe the orientation of a fault plane at a given location?

A)axis and plane
B)dip and strike
C)lateral and thrust
D)plunge and trend

Question 22

What is a thrust fault?

A)a low-angle normal fault
B)a low-angle reverse fault
C)a low-angle oblique fault
D)a low-angle strike-slip fault

Question 23

Oil can be trapped at the top of a dome if

A)there is a nearby basin.
B)there is an impermeable layer at the top of the dome.
C)the dome has been eroded.
D)the dome is part of an adjoining syncline.

Question 24

In an anticline,

A)the oldest rocks occur in the center and the limbs dip toward the center.
B)the oldest rocks occur in the center and the limbs dip away from the center.
C)the youngest rocks occur in the center and the limbs dip toward the center.
D)the youngest rocks occur in the center and the limbs dip away from the center.

Question 25

The surface that divides a fold into two symmetrical halves is called the

A)axial plane.
B)fault.
C)fold axis.
D)limb.

Question 26

An oblique-slip fault suggests

A)compressive forces only.
B)shear forces only.
C)tensional forces only.
D)shear forces combined with compressive or tensional forces.

Question 27

Oil is commonly trapped in

A)structural basins.
B)structural domes.
C)synclines.
D)anticlines.

Question 28

What type of structure is characterized by rock layers that dip radially toward a central point?

A)an anticline
B)a basin
C)a dome
D)a syncline

Question 29

What type of tectonic forces formed the Keystone thrust fault in southern Nevada?

A)compressive forces
B)tensional forces
C)shearing forces
D)all of the above

Question 30

Where do basins form?

A)where a part of the crust has been heated and subsequently cools and contracts
B)where tensional forces stretch the crust
C)where thick sequences of sediment are deposited
D)all of the above

Question 31

Which of the following geologic features is commonly formed in a region deformed by tensional tectonic forces?

A)an anticline
B)a thrust fault
C)a strike-slip fault
D)a rift valley

Question 32

An overturned fold is characterized by two limbs

A)at right angles to each other.
B)dipping in the same direction,with one limb tilted beyond vertical.
C)dipping steeply in opposite directions.
D)dipping gently in opposite directions.

Question 33

The total amount of shortening in an overthrust may exceed several

A)meters.
B)tens of meters.
C)hundreds of meters.
D)kilometers.

Question 34

Which of the following types of tectonic forces cause faulting?

A)compressive forces
B)shear forces
C)tensional forces
D)all of the above

Question 35

A rift valley is

A)a downfaulted block.
B)an eroded basin.
C)an eroded dome.
D)an upfaulted block.

Question 36

Upfolds,or arches,of layered rock are called

A)anticlines.
B)faults.
C)synclines.
D)unconformities.

Question 37

Older rocks crop out in the core of which of the structures listed below? I.anticline II.syncline III.dome IV.basin

A)structures I and II
B)structures I and III
C)structures III and IV
D)structures II and IV

Question 38

Which of the following statements about synclines is true?

A)The oldest rocks occur in the center and the limbs dip toward the center.
B)The oldest rocks occur in the center and the limbs dip away from the center.
C)The youngest rocks occur in the center and the limbs dip toward the center.
D)The youngest rocks occur in the center and the limbs dip away from the center.

Question 39

Which of the following correctly links the tectonic force with the expected type of faulting?

A)compression = normal faulting
B)shear = strike-slip faulting
C)tension = reverse faulting
D)tension + compression = oblique-slip faulting

Question 40

Cataclastic textures form in association with what types of geologic structures?

A)faults
B)joints
C)folds
D)all of the above

Question 41

How do geologists recognize faults in the field?

A)from scarps in the landscape
B)from folding
C)from strike
D)from general relief

Question 42

A diagram representing a vertical slice through Earth's crust is called a

A)geologic map.
B)geologic model.
C)subsurface picture.
D)geologic cross section.

Question 43

Which of the following map scales shows the largest area?

A)1:200
B)1:2000
C)1:20,000
D)1:200,000

Question 44

A fold that has a nonhorizontal fold axis is called a(n)________ fold.

A)symmetrical
B)asymmetrical
C)plunging
D)overturned

Question 45

The geologic history of an area is reconstructed using

A)geologic mapping.
B)geologic cross sections.
C)deduction of the deformation history.
D)geologic positioning.

Question 46

What sort of fault type is likely to form where shear forces combine with compressive or tensional forces?

A)a normal fault
B)a thrust fault
C)an oblique-slip fault
D)a strike-slip fault

Question 47

What is the scale on a map where 1 centimeter represents 1 kilometer?

A)1:1
B)1: 100
C)1:100,000
D)1000:1

Question 48

Development of mylonitic textures occurs with what other geologic process?

A)sedimentation
B)diagenesis
C)partial melting
D)metamorphism

Question 49

Which of the following does not affect rock behavior in regards to deformation?

A)rock type
B)temperature
C)speed
D)deformation style

Question 50

What basic source reveals the geometry of rock formations?

A)the geologic map
B)strike
C)the outcrop
D)dip

Question 51

One of the most spectacular displacements observed along the San Andreas fault line involves

A)a suite of metamorphic rocks.
B)volcanic lava flows.
C)a fold and thrust belt.
D)a dome.

Question 52

Which of the following statements is false?

A)Asymmetrical folds have dipping axial planes.
B)Synclines contain the youngest geologic units in the core.
C)Symmetrical folds have dipping axial planes.
D)Overturned folds have one limb that has rotated past vertical.

Question 53

Geologic maps are used to depict

A)the strike and dip of the rock units at Earth's surface.
B)the rock formations exposed on Earth's surface.
C)the orientation of geologic structures that deform rocks exposed at Earth's surface.
D)all of the above

Question 54

A mass of rock exposed at Earth's surface is called

A)crust.
B)bedrock.
C)outcrop.
D)exposure.

Question 55

On a map with a 1:2400 scale,what does 1 centimeter represent on the map?

A)1 centimeter
B)24 centimeters
C)240 centimeters
D)2400 centimeters

Question 56

Which of the following maps shows the most detail?

A)scale 1:100
B)scale 1:1000
C)scale 1:24,000
D)scale 1:1,000,000

Question 57

The Basin and Range province in the southwest United States is an area actively undergoing

A)crustal compression
B)crustal extension
C)crustal shearing
D)crustal mapping

Question 58

If erosion stripped the top off a dome,one would find

A)the oldest rocks exposed in the center.
B)the youngest rocks exposed in the center.
C)a linear pattern of rock outcrops.
D)the oldest rocks exposed in the center and a linear pattern of rock outcrops.

Question 59

The world's largest earthquakes occur along

A)normal faults in rift valleys.
B)megathrusts at subduction zones.
C)strike-slip faults along transform plate boundaries.
D)fold and thrust belts at continental collision zones.

Question 60

Faults and folds can range in scale from centimeters to

A)a few meters.
B)tens of meters.
C)a few kilometers.
D)tens of kilometers or more.

Question 61

Which of the following forces,when applied to the edges of a layer,will not produce a fold?

A)pushing together
B)pulling apart
C)pushing one edge up
D)pulling one edge down

Question 62

During continental tensional tectonics,crustal blocks tend to lean backward due to the development of _____ faults.

A)thrust
B)listric
C)shear
D)reverse

Question 63

What are two sides of a fold called where the fold axis is not horizontal?

A)dipping
B)tipped folds
C)leaning folds
D)plunging folds

Question 64

Geologists study deformation in rocks by looking at

A)thickness of layers.
B)folding of layers.
C)mineralogy of layers.
D)lateral extent of layers.

Question 65

When the axial plane of a fold is tilted beyond the vertical,it's called a(n)_____ fold.

A)nonvertical
B)horizontal
C)plunging
D)overturned

Question 66

The process of deformation does not include which of the following?

A)folding
B)faulting
C)melting
D)shearing

Question 67

When two blocks on either side of a fracture a ______ will turn into a _______.

A)dome; basin
B)fault; joint
C)joint; fault
D)anticline; syncline

Question 68

In a normal fault the hanging wall is formed on the side that moves

A)up dip.
B)down dip.
C)to the right of the strike.
D)to the left of the strike.

Question 69

Which of the following geologic structures has a hanging wall?

A)strike-slip fault
B)syncline
C)reverse fault
D)anticline

Question 70

The great San Andreas fault is an excellent example of

A)a fold and thrust belt.
B)an overthrust.
C)a megathrust.
D)shearing tectonics.

Question 71

When applied,_________ pressure is even in all directions.

A)confining
B)compressional
C)tensional
D)shear

Question 72

The two sides of a fold are called?

A)arms
B)legs
C)limbs
D)flaps

Question 73

Listric faults are a type of ______ fault.

A)thrust
B)reverse
C)shear
D)normal

Question 74

What is the main difference between a normal listric and normal fault?

A)the former is compressive and the latter is extensional
B)the fault blocks across the fault plane move in opposite directions
C)the fault plane for the former is curved but straight for the latter
D)the fault plane for the former is straight and the latter is curved

Question 75

In response to deformation brittle materials will _____ whereas ductile materials will ____.

A)expand; shrink
B)fold; fault
C)fault; fold
D)flow; fracture