Deck 11: Crags,cracks,and Crumples: Crustal Deformation and Mountain Building

Question 1

Shear stress at sufficient depth within a fault plane can induce plastic shear,forming a fine-grained metamorphic rock named ________.

A) ignimbrite
B) gneiss
C) mylonite
D) migmatite

Answer 1

C

Question 2

Which of the following is NOT an example of deformation?

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

Answer 2

D

Question 3

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.

Answer 3

A

Question 4

The distinction between joints and faults is that ________.

A) faults are joints that are greater than one square meter in areal extent
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 5

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 6

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

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

Question 7

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

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

Question 8

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

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

Question 9

Why do earthquakes occur only above the brittle/plastic transition depth?

A) Below the transition,the rocks are too hot.
B) Below the transition,the rocks break too easily.
C) Above the transition,the rocks are too hot.
D) Above the transition,the rocks will flow.

Question 10

Right-lateral and left-lateral are both examples of ________ faults.

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

Question 11

Which of these features would NOT help a geologist recognize a fault?

A) different rock units juxtaposed against each other
B) a small step on the landscape
C) a shattered rock consisting of visible angular fragments
D) regularly spaced quartz veins

Question 12

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

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

Question 13

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 14

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

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

Question 15

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

Question 16

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.

Question 17

Force per unit area is termed ________.

A) stress
B) strain
C) power
D) work

Question 18

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 19

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 20

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

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

Question 21

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

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

Question 22

The rocks in the image below have been plastically deformed,resulting in a(n)__________.

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

Question 23

How is tectonic foliation,such as elongation of quartz grains,oriented relative to the original bedding plane of a body of rock?

A) Foliation is parallel to original bedding.
B) Foliation is at about 45° to original bedding.
C) Foliation is perpendicular to original bedding.
D) Foliation can be at a variety of angles to original bedding.

Question 24

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 25

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

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

Question 26

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

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

Question 27

The central portion of high curvature on a fold is termed the fold ________.

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

Question 28

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 29

The rocks in the image below have been plastically deformed,resulting in a(n)__________.

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

Question 30

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

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

Question 31

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

A) Andes Mountains
B) Sierra Nevada Mountains
C) Italian Alps
D) Cascade Mountains

Question 32

If a fault plane is greater than 35° 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 33

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

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

Question 34

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 35

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

A) possesses an inclinometer,allowing the user to 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) needle points directly toward geographic north rather than geomagnetic north

Question 36

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 37

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

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

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

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 40

Which fault below could result from both strike-slip and dip-slip stresses?

A) A
B) B
C) C
D) D

Question 41

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

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

Question 42

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 43

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 44

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

Question 45

Compared to the Rocky Mountains,the Appalachian Mountains are a series of gently sloping hills.Have they always looked this way? Explain.

Question 46

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 47

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 48

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

Question 49

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 50

Which of the following statements is true of the Appalachian Mountains?

A) The Appalachian Mountains first formed during the continental collision that resulted in the formation of Pangaea.
B) The Appalachian Mountains are the result of the extension that formed the Mid-Atlantic Ridge.
C) The Appalachian Mountains are an accreted terrain,formed during subduction that preceded modern tectonics.
D) The Appalachian Mountains include remnants of structures and rocks that formed during three distinct collisional orogenies.

Question 51

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

Question 52

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 53

What is the primary reason why mountains substantially taller than Mt.Everest are unlikely to arise on 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 54

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 55

__________ 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 56

The __________ is the succession of the opening of an ocean basin to form a passive margin,later followed by the closing of that ocean basin to form a collisional orogeny.

A) cratonic shield
B) Wilson cycle
C) orogenesis cycle
D) continental rift

Question 57

Compare and contrast a cratonic shield and platform.

Question 58

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 59

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 60

How were the mountains in the Basin and Range Province formed?