Deck 9: Crags,cracks,and Crumples: Crustal Deformation and Mountain Building

Question 1

How is stress different from force?

A) Force is the stress applied per unit area.
B) Stress is the force applied per unit area.
C) Force comes from one direction,while stress comes from all directions.
D) They are not different: stress and force are synonymous.

Answer 1

B

Question 2

A body of rock affected by compressive stress will likely undergo ________.

A) shortening
B) stretching
C) shear strain
D) rotation

Answer 2

A

Question 3

Regularly spaced joints in an outcrop may indicate that an area ________.

A) is under intense shear stress
B) has experienced tension
C) is underlain by a thrust fault
D) is underlain by a magma body

Answer 3

B

Question 4

Under which condition would a body of rock be most likely to exhibit brittle behavior?

A) slow rate of deformation
B) low temperature
C) high temperature
D) high pressure

Question 5

We can describe the orientation of planar features such as faults and joints using measurement of the _______.

A) strike and dip
B) stress and strain
C) bearing and plunge
D) gap and displacement

Question 6

The term for a change in shape induced by stress is ________.

A) plastic deformation
B) pressure release
C) strain
D) metamorphosis

Question 7

A body of rock affected by tensile stress will likely undergo ________.

A) shortening
B) stretching
C) shear strain
D) rotation

Question 8

An episode of mountain building is termed a(n)________.

A) orogeny
B) phylogeny
C) aureole
D) slickenside

Question 9

Which of the following is NOT an example of deformation?

A) faults
B) folds
C) foliation
D) stratification

Question 10

How is stress different from strain?

A) Strain is a measure of the total displacement on a fault.
B) Stress is the change in shape of a rock due to applied strain.
C) Strain is the change in shape of a rock due to applied stress.
D) They are not different: stress and strain are synonymous.

Question 11

Which of these is NOT one of the components of deformation?

A) displacement
B) rotation
C) distortion
D) dissolution

Question 12

The majority of the Earth's mountains occur ________.

A) in belts called orogens
B) in the middle of cratons
C) isolated from each other
D) along passive margins

Question 13

The distinction between joints and faults is that ________.

A) faults are joints that extend across an entire orogen
B) faults are fractures along which displacement has occurred; displacement does not occur along joints
C) joints are fractures along which displacement has occurred; displacement does not occur along faults
D) there is no distinction; the two terms are synonymous

Question 14

Movement along faults often produces a rock formed from sharply angled rock fragments termed ________.

A) fault gouge
B) rock flour
C) fault breccia
D) slickenside

Question 15

How does the rate at which a body of rock is deformed affect its behavior?

A) A rock deformed quickly is likely to exhibit brittle behavior.
B) A rock deformed slowly is likely to exhibit brittle behavior.
C) The rate of deformation has no effect on a rock's behavior.
D) The rate of deformation is important only below the brittle/plastic transition.

Question 16

Why are earthquakes on continents most likely to occur above the brittle-plastic transition depth?

A) Below this transition,the rocks respond to stress by cracking and breaking
B) Below the transition,the rocks respond to stress by changing shape without breaking
C) Below the transition,the rocks are molten.
D) Below the transition,there are not stresses that could cause earthquakes.

Question 17

A mineral-filled crack in a rock is termed a _______.

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

Question 18

Under which of these conditions would a body of rock be more likely to exhibit plastic behavior?

A) low temperature
B) high temperature
C) low pressure
D) high rate of deformation

Question 19

If compressive stresses acting on a rock are greatest in a north-south direction,the rock will likely deform by shortening in a _________ direction.

A) east-west
B) up-down
C) north-south
D) random

Question 20

Normal,reverse,and thrust are all examples of ________ faults.

A) strike-slip
B) dip-slip
C) oblique-slip
D) lateral

Question 21

It is possible for offset along an oblique-slip fault to have both ________ and ________ components.

A) normal; reverse
B) right-lateral; left-lateral
C) normal; left-lateral
D) reverse; thrust

Question 22

Which type of a fault is the result of deformation to accommodate tensile stresses such as those that occur during rifting?

A) reverse
B) thrust
C) strike-slip
D) normal

Question 23

During the formation of Pangaea,Africa collided with North America and created the Appalachian Mountains.Which of the following mountain ranges is a modern analog to the ancient Appalachian Mountains?

A) Andes Mountains
B) Sierra Nevada Mountains
C) The Alps in Central Europe
D) Cascade Mountains

Question 24

A polished surface produced by scraping of rock along a fault is termed a(n)________.

A) orogeny
B) phylogeny
C) aureole
D) slickenside

Question 25

On a geologic map,if the contacts between sedimentary rock units form a series of parallel lines,with the oldest unit in the center,the underlying structure is a ________.

A) horizontal anticline
B) plunging anticline
C) horizontal syncline
D) plunging syncline

Question 26

Mountain ranges formed along subduction zones are formed,in part,by ___________ in the crust.

A) compression
B) stretching
C) extension
D) elongation

Question 27

What is the term for a fold in which layers show thickened hinges and thinned limbs,indicating plastic deformation during folding?

A) plunging fold
B) passive flow fold
C) foliation
D) flexural slip fold

Question 28

If you stand on one side of a strike-slip fault and the block on the other side of the fault has moved to your left,this is known as a(n)________.

A) oblique fault
B) dip-slip fault
C) right lateral fault
D) left lateral fault

Question 29

A geologist's compass differs from the more widely known orienteering compass in that the geologist's compass ________.

A) can measure dip and plunge angles
B) contains a barometer that warns the geologist of approaching storms
C) can chemically analyze rock samples in the field
D) can determine elevation above sea level

Question 30

If a fault plane is greater than 30° from horizontal and the hanging wall block moves upward relative to the footwall block,the fault is called a ________ fault.

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

Question 31

Normal faulting is most often associated with mountain building along ___________ boundaries,whereas reverse faulting is generally observed at ___________ boundaries.

A) divergent; transform
B) transform; convergent
C) convergent; divergent
D) divergent; convergent

Question 32

On a geologic map,if the contacts between sedimentary rock units form a bull's-eye pattern of concentric circles,with the oldest unit in the center,the underlying structure is a(n)________.

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

Question 33

In the image below,the rocks have been bent into an elongate arch.This is an example of a(n)________.

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

Question 34

The sides of a fold,where curvature is at a minimum,are termed ________.

A) branches
B) limbs
C) axial planes
D) hinges

Question 35

What is term for a fold in which layers bend without changing thickness,indicating slip between layers during folding?

A) plunging fold
B) passive flow fold
C) foliation
D) flexural slip fold

Question 36

On a geologic map,if the contacts between sedimentary rock units form a bull's-eye pattern of concentric circles,with the youngest unit in the center,the underlying structure is a(n)________.

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

Question 37

On a geologic map,the beds of an eroded anticline will be _________ near the fold hinge compared to further from the hinge.

A) younger
B) older
C) less deformed
D) steeply dipping

Question 38

In the image below,the rocks have been bent into an elongate trough.This is a(n)________.

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

Question 39

In a ________ fault,the fault plane is non-vertical and the hanging wall block moves downward relative to the footwall block.

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

Question 40

The portion along a fold where curvature is the greatest is termed the fold ________.

A) limb
B) hinge
C) midsection
D) thorax

Question 41

What are the three components of deformation? Briefly explain each.

Question 42

Compared to the Rocky Mountains,the Appalachian Mountains are a series of lower-elevation hills with more gentle slopes.Have they always had these differences in topography? Explain.

Question 43

Compare and contrast a cratonic shield and platform.

Question 44

What types of geologic structures would you expect to find in an area that had undergone compression?

Question 45

The formation of the Basin and Range Province,a fault-blocked mountain range in Utah,Nevada,and Arizona,is associated with which of the following processes?

A) continental rifting
B) continental collision
C) fold and thrust faulting
D) subduction zone volcanism

Question 46

What is the primary reason why mountains substantially taller than Mt.Everest are unlikely to arise on the Earth?

A) The high geothermal gradient in the crust causes mountains to collapse under their own weight.
B) Exhumation proceeds faster than uplift.
C) Extreme elevations cause chemical weathering to outpace uplift.
D) Uplift is limited by the rate of subduction.

Question 47

Regions of continents that have NOT been subjected to orogeny during the past 1 billion years are termed ________.

A) exotic terranes
B) accreted terranes
C) cratons
D) cratonic platforms

Question 48

What is the difference between a dip-slip fault and a strike-slip fault? Describe each and give specific examples (use sketches if that helps).

Question 49

Draw a cross section of a normal and reverse fault.For each,list the stress involved and change in the length of the crust,if any.

Question 50

Which of these properly illustrates the principle of isostasy?

A) High-density crust floats on top of low-density mantle.
B) Mountains stand high because they are gravitationally balanced by their deep crustal roots.
C) When weight is added to the crust,the crust responds by rebounding upward.
D) When material is removed from the crust,the crust maintains the new,lower elevation.

Question 51

The accreted terranes that are added to a continent during orogeny are _______ than the cratons of the continent's interior.

A) less deformed
B) of higher metamorphic grade
C) older
D) younger

Question 52

Compare and contrast domes and basins.If both are composed solely of sedimentary beds that have been eroded such that the ground surface is level,how would you identify each?

Question 53

What can be said about the rates of uplift and erosion in a mountain that is gaining elevation? In a mountain decreasing in elevation? What is the ultimate fate of all mountains on the Earth?

Question 54

__________ is the balance between the weight of a mountain range and the buoyancy provided by the underlying mantle.

A) Delamination
B) Suture
C) Isostasy
D) Orogen

Question 55

On a geologic map,cratonic basins,where thick sequences of sedimentary rocks overly the Precambrian basement,show the _________ rocks toward the center of the basin.

A) oldest
B) youngest
C) thinnest
D) most deformed

Question 56

What can be said about a mountain range that is being uplifted at 2 cm/year but is not growing any taller?

A) The crustal root is thinning at the same rate as the uplift.
B) The crustal root is thickening faster than the uplift.
C) The rate of erosion is the same as the rate of uplift.
D) The rate of erosion is higher than the rate of uplift.

Question 57

There are many ways in which uplift can occur,but all of them reflect ________.

A) compressional forces
B) the effects of weathering and erosion
C) subduction zone processes
D) the lithosphere's tendency to achieve isostasy

Question 58

Contrast brittle and plastic deformation.Cite an example of a structure associated with each.

Question 59

Regions where Precambrian metamorphic rocks are exposed at the surface are termed ________.

A) shields
B) cratonic platforms
C) convergent margins
D) domes

Question 60

What is the plate tectonic setting that formed the mountains of the Basin and Range Province,and what type of faulting has this resulted in?