Deck 9: Deformation, Mountain Building, and the Continents

Question 1

What is isostatic rebound? Give an example.

Answer 1

Isostatic rebound is the re-equilibration of the crust by rebounding to the level at which it "floats" again in the mantle after a mass has been removed.The melting of glaciers after the end of the ice age has caused the crust they were sitting on to rebound upward.

Question 2

How can you tell a dome from a basin?

Answer 2

In a dome,all of the folded strata dip outward from a central point (as opposed to outward from a line as in an anticline),and the oldest exposed rocks are at the center of the fold.In contrast,a basin has all strata dipping inward toward a central point,and the youngest exposed rocks are at the fold's center.

Question 3

Briefly explain why,according to the principle of isostasy,continental crust floats higher than oceanic crust.

Answer 3

A mass,such as the continental crust that "floats" on an underlying mass,should do so at an equilibrium level,such that it extends at least as far beneath the upper level of the underlying material as it does above the surface of that material.

Question 4

How could you tell an eroded plunging anticline from an eroded plunging syncline?

Question 5

Why is the study of deformation and deformed rock important?

Question 6

What factors are involved for a rock to behave as a brittle substance,and what factors cause it to behave plastically?

Question 7

If you observe steeply inclined sedimentary rocks,what can you conclude?

Question 8

What happens first when a stress is applied to a rock? What two things could happen if the stress continues to the next step?

Question 9

How can you tell if a strike-slip fault is right- or left-lateral?

Question 10

Why does continental crust stand higher than oceanic crust?

Question 11

How do continents grow? What material is added to them and how?

Question 12

What is deformation,and what causes it?

Question 13

What are the three types of stress,and how do they affect rocks?

Question 14

What are stress and strain? How are they related to deformation?

Question 15

If the mantle transmits S-waves,then how can it behave like a liquid,as implied by the principle of isostasy?

Question 16

What is strike? What is dip? How are they measured in rock layers?

Question 17

How did the monocline in the Bighorn Mountains in Wyoming form?

Question 18

Describe the plate tectonics processes and associated stresses that have led to the formation of the Himalayas,the world's largest mountain range?

Question 19

What is the law of universal gravitation? Why is gravitational attraction not the same everywhere on the surface of Earth?

Question 20

What is an orogeny? What does a theory of orogeny need to explain?

Question 21

What is meant when rocks are said to be deformed (fractured or folded)?

Question 22

What happens if some of the above water portion of an iceberg melts?

Question 23

What are the three types of stress?

Question 24

What happens if a rock is strained beyond its elastic limit?

Question 25

What are some geologic processes that accompany orogenesis at oceanic-oceanic convergent plate boundaries?

Question 26

When is a fold described as a plunging fold?

Question 27

What does tension stress result in?

Question 28

What is the difference between a thrust fault and a reverse fault?

Question 29

What is the distinction between the hanging wall block and the footwall block of a fault?

Question 30

What is the difference between stress and strain?

Question 31

What does shear stress result from?

Question 32

What is meant when a fold is described as being recumbent?

Question 33

What are terranes?

Question 34

What is the difference between faults and joints?

Question 35

What does tension stress result from?

Question 36

What does compression stress result from?

Question 37

What role do geologists play in engineering large structures like bridges and power plants?

Question 38

What are some ways in which mountains form?

Question 39

What is the difference between brittle and ductile rocks?

Question 40

What is the dip of an inclined layer of rock?

Question 41

A fold that has axial beds that are younger than those of its limbs and limbs that dip toward its axis is called a(n)____________________.

Question 42

Each half of a fold is known as a(n)____________________.

Question 43

An episode of mountain building is known as a(n)____________________.

Question 44

The type of fold that forms traps for most of the world's produced petroleum is a(n)____________________.

Question 45

Deformation caused by stress that exceeds a material's internal strength is known as ____________________.

Question 46

The principle that Earth's crust is in floating equilibrium with the denser mantle below is known as ____________________.

Question 47

If both limbs of a fold dip in the same direction,the fold is ____________________.

Question 48

A fold is the result of ____________________ deformation.

Question 49

In an anticline,the beds in its axial region are ____________________ in age than the beds of its limbs,and all strata dip ____________________ the axis.

Question 50

A(n)____________________ is a circular or oval fold in which the strata are warped downwardly in the center and the beds on the flanks are ____________________ in age than the strata in the interior.

Question 51

Strike-slip faults are caused by ____________________ forces.

Question 52

The direction of a line formed by the intersection of a horizontal plane with the plane of a layer of rock is called ____________________.

Question 53

An up-arched fold is a(n)____________________.

Question 54

Rocks that are now tilted were deposited ____________________.

Question 55

Small accreted lithospheric blocks of foreign origin that differ completely from the rocks in surrounding regions are called ____________________.

Question 56

A simple bend or flexure in an otherwise horizontal rock layer is called a(n)____________________.

Question 57

In a(n)____________________,the youngest rocks are in the center,and the oldest are on the outside.In a(n)____________________,the oldest rocks are in the center,and the youngest are on the outside.

Question 58

A(n)____________________ divides a fold into two halves.

Question 59

The truly large mountain systems of the world are found at ____________________ plate boundaries.

Question 60

Force applied to a given area is known as ____________________.

Question 61

The thickest crust is found:

A)beneath mountains.
B)at the old stable portions of the continents.
C)at the continental margins.
D)at the old stable portions of the ocean basins.
E)at the mid-oceanic ridge spreading centers.

Question 62

An oval fold in which strata are up-arched and the younger rocks are found in the interior is a basin.

Question 63

Movement along the San Andreas is:

A)compressional.
B)tensional.
C)right-lateral.
D)left-lateral.
E)vertical.

Question 64

The type of strain that occurs depends not only on the kind of stress applied,but also on the:

A)amount of pressure and degree of temperature.
B)rock type.
C)duration of the stress
D)A and C
E)A and B

Question 65

If you're standing on ice above a pond and you hear a crack,you should:

A)remain motionless until the cracking stops.
B)lie down on the ice to distribute your weight more broadly on the ice.
C)run as fast as you can to shore.
D)not worry because the ice will not break.
E)prepare for a swim.

Question 66

Dip-slip faults include:

A)normal faults.
B)reverse faults.
C)thrust faults.
D)normal and reverse faults.
E)normal,reverse and thrust faults.

Question 67

Volcanic island arcs are characteristic of which type of convergent plate boundaries?

A)continental-continental
B)continental-oceanic
C)oceanic-oceanic
D)continental-oceanic AND oceanic-oceanic
E)continental-continental;continental-oceanic AND oceanic-oceanic

Question 68

Continents grow and evolve by addition of felsic and mafic crust-a process known as:

A)addition.
B)accretion.
C)concretion.
D)convergence.
E)conformation.

Question 69

Which of the following have become terranes?

A)island arcs and ocean ridges
B)seamounts
C)fragments of other continents
D)island arcs,ocean ridges and seamounts
E)island arcs,ocean ridges,seamounts and fragments of other continents

Question 70

When an isolated mountain range occurs in the interior of a continent,one may infer that the range formed by:

A)the collision of two continental plates.
B)compressive forces acting on the opposing margins of a single plate.
C)the rifting of the continent.
D)the growth of a volcanic arc.
E)the collision of two continental plates or the growth of a volcanic arc

Question 71

Most folding of rocks occurs near the surface.

Question 72

If you have one foot on either side of a fault with a vertical dip and the right block moves toward you,what type of fault are you straddling?

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

Question 73

Oceanic-continental plate orogenesis can be recognized in the geological record by a(n):

A)accretionary wedge containing ophiolites.
B)landward belt of volcanoes and batholiths.
C)inland zone of block faults.
D)accretionary wedge containing ophiolites AND landward belt of volcanoes and batholiths.
E)all of these.

Question 74

Uplifted blocks are called:

A)tensional blocks.
B)grabens.
C)horsts.
D)fault blocks.
E)graves.

Question 75

At the San Andreas fault,the Pacific Plate is moving northwest relative to the southeast moving North American Plate.Therefore,movement along the San Andreas is:

A)compressional
B)tensional
C)right-lateral
D)left-lateral
E)vertical

Question 76

In a reverse fault,the:

A)hanging wall block goes up relative to the footwall block.
B)hanging wall block goes down relative to the footwall block.
C)hanging wall block and footwall block remain in the same position vertically.
D)two sides of the fault slide past each other horizontally.
E)two sides of the fault move away from each other.

Question 77

Rocks that are tilted were deposited:

A)on a slope in their present orientation.
B)in an unknown orientation and then were tilted into their current position.
C)horizontally and then were tilted into their current orientation.
D)vertically and then were tilted into their current orientation.
E)on the continental shelf and then uplifted.

Question 78

The hanging wall block moves downward relative to the footwall block in a normal fault.

Question 79

A cliff formed as a consequence of vertical movement along a fault is a fault scarp.

Question 80

A fault with both dip-slip and strike-slip movement is classified as a thrust fault.