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?

Accepted Answer

Given the fault plane dips steeply to the west and Mesozoic rocks (younger) are found east of the fault while Paleozoic rocks (older) are found west of the fault, with the movement being dip-slip, this indicates that the hanging wall moved up relative to the footwall. This is characteristic of a reverse fault, where compression causes the older strata to be pushed over the younger strata.

Question 2

The difference between a fault and a joint is that

Accepted Answer

Rocks on either side of a fault have moved relative to each other, which is a key characteristic distinguishing faults from joints. In contrast, joints are fractures where there has been no significant movement of the rock on either side.

Question 3

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

Accepted Answer

The San Andreas fault is a right-lateral strike-slip fault, where the two sides of the fault slide past each other horizontally.

Question 4

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

Accepted Answer

A right-lateral fault is a type of strike-slip fault where the displacement of the earth's crust is horizontal, along the fault plane, and parallel to the fault line, distinguishing it from dip-slip faults (normal, reverse, and thrust faults) where the movement is primarily vertical.

Question 5

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

Accepted Answer

Mylonites form deep in the Earth's crust where high pressure and temperature conditions lead to ductile deformation, resulting in a fine-grained, foliated texture characteristic of mylonitic rocks.

Question 6

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

Accepted Answer

A joint is a fracture in rock along which no significant movement has occurred, distinguishing it from a fault where movement along the fracture is a defining characteristic.

Question 7

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

Accepted Answer

The San Andreas fault is a result of shearing forces, which occur when two plates slide past each other horizontally. This lateral movement is characteristic of transform boundaries, like the San Andreas Fault, where the Pacific Plate and the North American Plate meet.

Question 8

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

Accepted Answer

The strike is the line formed by the intersection of an inclined sedimentary layer and a horizontal plane, representing the direction of the layer as it appears on the Earth's surface.

Question 9

What type of material undergoes smooth,continuous plastic deformation?

Accepted Answer

Ductile materials undergo smooth, continuous plastic deformation. This is because they can sustain significant deformation under stress before failure, unlike brittle materials which fracture with minimal deformation. Cataclastic deformation refers to the process where rocks are fractured and crushed, not undergoing smooth, continuous deformation.

Question 10

Which of the following statements about rock deformation is false?

Accepted Answer

Rocks under high surrounding pressure are more likely to deform ductilely, as the pressure helps the rocks to bend or flow rather than fracture, which is opposite to what is stated in option D.

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?

Accepted Answer

Shearing forces are responsible for pushing two sides of a body in opposite directions, causing them to slide horizontally past each other. This type of force is commonly associated with strike-slip faults in tectonic plate boundaries.

Question 12

Reverse faults form in response to ______ forces.

Accepted Answer

Reverse faults form in response to compressive forces, where the crust is being pushed together, causing one block of rock to be pushed up relative to the other.

Question 13

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

Accepted Answer

The duration of the deformation event is the most difficult to simulate in a laboratory experiment because natural deformation processes can take thousands to millions of years, whereas laboratory experiments are significantly constrained by practical time frames.

Question 14

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

Accepted Answer

The answer of If a basalt unit near the surface...

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?

Accepted Answer

A normal fault is characterized by the movement of the rocks above the fault plane downward relative to the rocks below the fault plane, typically due to extensional forces.

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

Accepted Answer

Plastic deformation in rocks, including marble, is more likely at higher temperatures and higher confining pressures. These conditions allow the rock to deform ductilely rather than fracturing brittlely.

Question 17

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

Accepted Answer

Compressive forces tend to squeeze and shorten a rock body, acting to compress and fold the rock layers.

Question 18

The dip of a unit represents the

Accepted Answer

The dip of a geological unit refers to the angle at which the bed inclines from the horizontal, indicating the steepness of the slope of rock layers.

Question 19

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

Accepted Answer

The way a rock deforms, whether in a brittle or ductile manner, is influenced by a combination of factors including the temperature at which the deformation occurs, the type of rock, and the rate at which the deformation happens. High temperatures and slow deformation rates tend to favor ductile deformation, while low temperatures and rapid deformation rates favor brittle deformation. Different rock types also have varying propensities for either brittle or ductile behavior based on their composition and structure.

Question 20

What types of forces dominate at convergent plate margins?

Accepted Answer

At convergent plate margins, plates move towards each other, leading to compressive forces that dominate as they push against one another.

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