Deck 9: Deformation, Mountain Building, and the Continents

Question 1

Why is the study of deformation and deformed rock formations important?

Answer 1

Deformed rock layers provide a record of the types and intensities of forces that operated during the rock's history, which can inform us about the geologic history of the region. Civil engineers need to study the rock where they are planning to build sites for dams, bridges, and other constructions, especially if the deformation is recent or ongoing. Also, exploring for petroleum and natural gas is crucial in understanding deformed rock formations.

Question 2

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

Answer 2

Stress results from forces applied to a given area of rock. If the stress on the rock exceeds the rock's internal strength, the rock undergoes strain. Strain is how rocks respond to stress; strain and deformation are synonyms.

Question 3

What is isostatic rebound? Give an example.

Answer 3

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 with the release of pressure similar to when a person is lying on a mattress that exerts pressure and when a person is not lying on the mattress the pressure is released and mattress springs back to its original shape.

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

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

Question 11

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 12

Why does continental crust stand higher than oceanic crust?

Question 13

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

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

What is deformation and what causes it?

Question 20

How can you tell a dome from a basin?

Question 21

What are terranes?

Question 22

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

Question 23

What is the difference between stress and strain?

Question 24

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

Question 25

What does compression stress result from?

Question 26

What is the difference between brittle and ductile rocks?

Question 27

When is a fold described as a plunging fold?

Question 28

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

Question 29

What does tension stress result from?

Question 30

What is the dip of an inclined layer of rock?

Question 31

What is the difference between faults and joints?

Question 32

What are some ways in which mountains form?

Question 33

What role do geologists play in construction of structures like bridges and power plants?

Question 34

What is the distinction between normal and reverse fault?

Question 35

What are the three types of stress?

Question 36

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

Question 37

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

Question 38

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

Question 39

What does shear stress result from?

Question 40

What does tension stress result in?

Question 41

Strike-slip faults are caused by ____________________ forces.

Question 42

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

Question 43

A fold is the result of ____________________ deformation.

Question 44

A(n) ____________________ divides a fold into more or less two equal halves.

Question 45

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

Question 46

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

Question 47

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 48

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

Question 49

Rocks that are now tilted were initially deposited ____________________.

Question 50

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

Question 51

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

Question 52

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

Question 53

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

Question 54

Force applied to a given area is known as ____________________.

Question 55

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 56

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 57

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

Question 58

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

Question 59

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

Question 60

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

Question 61

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 62

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 63

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

Question 64

Continents grow and evolve by addition of felsic and mafic crust ¾ a process known as:

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

Question 65

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 66

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

Question 67

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 68

Oceanic-continental plate orogenies 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 69

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 70

Uplifted blocks are called:

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

Question 71

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

Question 72

Most folding of rocks occurs near the surface.

Question 73

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 74

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 75

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 76

Movement along the San Andreas is:

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

Question 77

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

Question 78

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 79

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 80

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.