Earth Science Quiz: Fault Types And Stress

What this quiz covers

This quiz focuses on Fault Types And Stress, giving you a quick way to practice the rules, question types, and explanations that matter most for Earth Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Reverse faulting at a convergent plate boundary.
2. Normal faulting in a continental rift zone. (correct answer)
3. Strike-slip faulting at a transform plate boundary.
4. Thrust faulting in a continental collision zone.

Explanation: When the maximum principal stress (σ1) is vertical, the crust is being pushed down by gravity more forcefully than it is being squeezed horizontally. This leads to horizontal extension (tensional stress). Tensional stress regimes produce normal faults. Continental rift zones, like the East African Rift, are prime examples of such settings.

Question 2

1. The maximum compressive stress (σ1) is oriented northwest-southeast, parallel to the fault.
2. The maximum compressive stress (σ1) is oriented northeast-southwest, perpendicular to the fault.
3. The maximum compressive stress (σ1) is oriented roughly north-south, at an angle to the fault. (correct answer)
4. The intermediate compressive stress (σ2) is horizontal, and the maximum stress (σ1) is vertical.

Explanation: In a shear regime that produces strike-slip faulting, the maximum (σ1) and minimum (σ3) principal stresses are both horizontal, while the intermediate stress (σ2) is vertical. The faults typically form at an angle of about 30-45 degrees to the direction of maximum compression. For the San Andreas Fault system, the Pacific plate is moving northwest relative to the North American plate. This movement is driven by a maximum compressive stress (σ1) oriented roughly north-south, which is at an angle to the northwest-striking fault itself, creating the right-lateral shear.

Question 3

1. A stress regime where the maximum principal stress is perfectly vertical and the minimum is horizontal.
2. A purely compressional environment where stress is applied exactly perpendicular to the fault strike.
3. A transtensional regime, where overall shear is combined with a component of extension. (correct answer)
4. A purely tensional environment where stress is applied exactly perpendicular to the fault strike.

Explanation: Oblique-slip motion requires a combination of shear stress (causing strike-slip) and either tensional or compressional stress (causing dip-slip). A transtensional regime combines transform (shear) motion with tensional (extensional) motion, resulting in both strike-slip and normal dip-slip components. Similarly, a transpressional regime combines shear and compression. The other options describe pure stress regimes that would produce pure normal, reverse, or strike-slip faults, not oblique-slip.

Question 4

1. primarily dip-slip motion under either a compressional or tensional regime. (correct answer)
2. primarily strike-slip motion under a shear regime.
3. oblique-slip motion under a transtensional regime.
4. no significant movement, as the grooves are from glacial scouring.

Explanation: Slickensides are scratches or grooves on a fault surface that indicate the direction of relative movement. If these grooves plunge directly down the dip of the fault, it means the movement was up or down the fault plane, which is defined as dip-slip motion. Dip-slip motion occurs in both normal faults (tensional stress) and reverse faults (compressional stress). Without knowing which block moved up or down, we cannot distinguish between the two, but we can confidently identify the motion as dip-slip.

Question 5

1. Normal faults resulting from a tensional stress regime.
2. Thrust faults resulting from a compressional stress regime. (correct answer)
3. Strike-slip faults resulting from a shear stress regime.
4. Reverse faults resulting from a tensional stress regime.

Explanation: The presence of folds and the placement of older rocks over younger rocks are classic indicators of crustal shortening caused by compression. A fault that places older rocks over younger rocks is a reverse fault. When a reverse fault has a low dip angle (typically <45°, and especially <30°), it is specifically called a thrust fault. Therefore, the observations are best explained by thrust faulting under a compressional stress regime.

Question 6

1. Extensive strike-slip faulting due to regional north-south shear stress.
2. Large-scale thrust faulting due to east-west compressional stress.
3. Widespread normal faulting due to east-west tensional (extensional) stress. (correct answer)
4. Complex folding and reverse faulting due to north-south compressional stress.

Explanation: The 'basin and range' topography, with its alternating down-dropped blocks (grabens, which form valleys or basins) and uplifted blocks (horsts, which form mountain ranges), is the classic expression of large-scale crustal extension. This extension is accommodated by normal faulting. Since the ranges trend north-south, the tensional stress must be oriented perpendicular to them, in an east-west direction.

Question 7

1. Maximum principal stress (σ1) is north-south; minimum principal stress (σ3) is vertical. (correct answer)
2. Maximum principal stress (σ1) is vertical; minimum principal stress (σ3) is north-south.
3. Maximum principal stress (σ1) is east-west; minimum principal stress (σ3) is north-south.
4. Maximum principal stress (σ1) is north-south; intermediate principal stress (σ2) is vertical.

Explanation: Reverse faults are caused by compressional stress, where the maximum principal stress (σ1) is horizontal and the minimum principal stress (σ3) is vertical. The compression acts perpendicular to the strike of the fault. Since the fault strikes east-west, the maximum compression (σ1) must be oriented north-south to cause the shortening.

Question 8

1. The fault will be reactivated as a normal fault.
2. The fault will be reactivated as a reverse fault. (correct answer)
3. The fault will be reactivated as a right-lateral strike-slip fault.
4. The fault will remain inactive, and a new set of east-west striking faults will form.

Explanation: The imposed stress is east-west compression. This stress will push the eastern and western sides of the region together. For a fault that dips to the west, the block on the west side is the hanging wall. The east-west compression will push the hanging wall block up the fault plane relative to the footwall block. This type of motion defines a reverse fault. Pre-existing planes of weakness, like old faults, are often reactivated before new ones are created.

Question 9

1. 100 meters
2. 141 meters
3. 200 meters (correct answer)
4. 282 meters

Explanation: First, determine the vertical displacement, or throw. The coal seam is at 500m on one side and 700m on the other, so the throw is 700m - 500m = 200m. The throw, heave (horizontal extension), and fault dip are related by trigonometry. Specifically, tan(dip angle) = throw / heave. Since the dip angle is 45 degrees, and tan(45°) = 1, the throw must be equal to the heave. Therefore, the heave is also 200 meters.

Question 10

1. Thrust faults, as the surrounding rock is compressed inward after the magma evacuates.
2. Ring faults, which are a form of normal fault, due to tensional stress as the roof loses support. (correct answer)
3. Strike-slip faults, as the roof shears and rotates into the empty chamber.
4. Reverse faults, as the magma pressure from below pushes the surrounding rock upward before the eruption.

Explanation: When a magma chamber empties, the overlying rock (the roof) loses its support. Gravity then becomes the dominant force, pulling the roof block downward. This creates a tensional stress regime in the rock surrounding the unsupported area. The crust fails along steeply dipping normal faults that form a circle or ring, allowing the central block to subside. These are called ring faults.

Question 11

1. A compressional 'restraining bend' with uplift, reverse faults, and folds. (correct answer)
2. An extensional 'releasing bend' with subsidence, a pull-apart basin, and normal faults.
3. A simple continuation of the strike-slip fault with no change in topography.
4. A volcanic arc due to melting caused by the increased friction at the bend.

Explanation: Imagine tracing the motion on a right-lateral fault. As you move along one segment and have to 'step' left to get to the next segment, the blocks on either side are being pushed into each other in the step-over region. This creates a zone of localized compression, known as a restraining bend or a transpressional zone. The crust in this zone will shorten and thicken, leading to uplift, folding, and reverse/thrust faulting.

Question 12

1. Reverse faulting, due to the compression of magma being forced into the crust.
2. No faulting, because the magma intrusion causes ductile deformation instead of brittle failure.
3. Strike-slip faulting, as the two sides of the dike slide past each other.
4. Normal faulting, due to localized extension as the crust is pushed apart by the dike. (correct answer)

Explanation: When analyzing volcanic processes, you need to understand how magma intrusions create stress in the surrounding rock. A dike is a sheet-like intrusion that cuts vertically through existing rock layers, literally forcing the crust apart as it propagates upward. As the dike intrudes, it creates a localized zone of extension directly above it. Think of it like inserting a wedge into a crack – the material on either side must move apart to accommodate the new volume. This extensional stress causes the overlying rock to stretch and thin, leading to normal faulting where one block drops down relative to another along inclined fault planes. The surface expression would show parallel normal faults running along the same orientation as the dike below. Option A is incorrect because reverse faulting occurs under compression, not the extension created by dike intrusion. While magma does exert pressure, the dominant effect is pulling the crust apart, not squeezing it together. Option B misunderstands the brittle nature of shallow crustal rocks. Even though deeper rocks may deform ductilely, the upper crust typically responds to dike intrusion with brittle fracturing and faulting. Option C incorrectly suggests strike-slip motion. While the sides of the dike do separate, they move apart perpendicular to the dike walls, not parallel to them as in strike-slip faulting. Remember this key principle: dike intrusions create extension perpendicular to their orientation, and extension in the brittle crust produces normal faults. Look for this pattern whenever volcanic processes involve vertical magma intrusions.

Question 13

1. Reverse faulting at a convergent plate boundary.
2. Normal faulting in a continental rift zone. (correct answer)
3. Strike-slip faulting at a transform plate boundary.
4. Thrust faulting in a continental collision zone.

Explanation: When the maximum principal stress (σ1) is vertical, the crust is being pushed down by gravity more forcefully than it is being squeezed horizontally. This leads to horizontal extension (tensional stress). Tensional stress regimes produce normal faults. Continental rift zones, like the East African Rift, are prime examples of such settings.

Question 14

1. Extensive strike-slip faulting due to regional north-south shear stress.
2. Large-scale thrust faulting due to east-west compressional stress.
3. Widespread normal faulting due to east-west tensional (extensional) stress. (correct answer)
4. Complex folding and reverse faulting due to north-south compressional stress.

Explanation: The 'basin and range' topography, with its alternating down-dropped blocks (grabens, which form valleys or basins) and uplifted blocks (horsts, which form mountain ranges), is the classic expression of large-scale crustal extension. This extension is accommodated by normal faulting. Since the ranges trend north-south, the tensional stress must be oriented perpendicular to them, in an east-west direction.

Question 15

1. Maximum principal stress (σ1) is north-south; minimum principal stress (σ3) is vertical. (correct answer)
2. Maximum principal stress (σ1) is vertical; minimum principal stress (σ3) is north-south.
3. Maximum principal stress (σ1) is east-west; minimum principal stress (σ3) is north-south.
4. Maximum principal stress (σ1) is north-south; intermediate principal stress (σ2) is vertical.

Explanation: Reverse faults are caused by compressional stress, where the maximum principal stress (σ1) is horizontal and the minimum principal stress (σ3) is vertical. The compression acts perpendicular to the strike of the fault. Since the fault strikes east-west, the maximum compression (σ1) must be oriented north-south to cause the shortening.

Question 16

1. primarily dip-slip motion under either a compressional or tensional regime. (correct answer)
2. primarily strike-slip motion under a shear regime.
3. oblique-slip motion under a transtensional regime.
4. no significant movement, as the grooves are from glacial scouring.

Explanation: Slickensides are scratches or grooves on a fault surface that indicate the direction of relative movement. If these grooves plunge directly down the dip of the fault, it means the movement was up or down the fault plane, which is defined as dip-slip motion. Dip-slip motion occurs in both normal faults (tensional stress) and reverse faults (compressional stress). Without knowing which block moved up or down, we cannot distinguish between the two, but we can confidently identify the motion as dip-slip.

Question 17

1. The fault will be reactivated as a normal fault.
2. The fault will be reactivated as a reverse fault. (correct answer)
3. The fault will be reactivated as a right-lateral strike-slip fault.
4. The fault will remain inactive, and a new set of east-west striking faults will form.

Explanation: The imposed stress is east-west compression. This stress will push the eastern and western sides of the region together. For a fault that dips to the west, the block on the west side is the hanging wall. The east-west compression will push the hanging wall block up the fault plane relative to the footwall block. This type of motion defines a reverse fault. Pre-existing planes of weakness, like old faults, are often reactivated before new ones are created.

Question 18

1. A compressional 'restraining bend' with uplift, reverse faults, and folds. (correct answer)
2. An extensional 'releasing bend' with subsidence, a pull-apart basin, and normal faults.
3. A simple continuation of the strike-slip fault with no change in topography.
4. A volcanic arc due to melting caused by the increased friction at the bend.

Explanation: Imagine tracing the motion on a right-lateral fault. As you move along one segment and have to 'step' left to get to the next segment, the blocks on either side are being pushed into each other in the step-over region. This creates a zone of localized compression, known as a restraining bend or a transpressional zone. The crust in this zone will shorten and thicken, leading to uplift, folding, and reverse/thrust faulting.

Question 19

1. In any stress regime, faults form parallel to the direction of maximum principal stress (σ1).
2. Compressional stress always results in a single, large-scale thrust fault rather than a network of smaller faults.
3. Strike-slip faults are unique in that they are caused by torsional stress rather than compressive or tensional stress.
4. Tensional stress causes the crust to fail in shear, creating normal faults at an angle to the stress. (correct answer)

Explanation: When you encounter questions about stress and fault formation, focus on understanding how different stress regimes cause rocks to fail and create specific fault geometries. Tensional stress pulls the crust apart, causing it to fail along inclined planes rather than vertically. This creates normal faults where the hanging wall moves down relative to the footwall, typically at angles between 45-65° from horizontal. The key insight is that even though the stress is tensional (pulling), the actual failure occurs through shear along these angled planes because that's where the rock is weakest. Let's examine why the other options miss the mark. Choice A incorrectly states that faults form parallel to maximum principal stress (σ1). In reality, faults typically form at angles to σ1 - usually around 30° for optimal shear failure. Choice B oversimplifies compressional faulting. While compression does create thrust faults, it commonly produces complex networks of multiple faults rather than a single large one, depending on factors like rock type and stress magnitude. Choice C contains a fundamental misconception about strike-slip faults. These faults actually result from horizontal compressive or shear stress, not "torsional stress" - they form when the maximum and minimum principal stresses are both horizontal. Remember this pattern: the type of fault depends on the orientation of principal stresses, but faults rarely form parallel to stress directions. Instead, they develop along planes of weakness where shear failure is most likely to occur, which is typically at specific angles to the stress field.

Question 20

1. Reverse faulting, due to the compression of magma being forced into the crust.
2. No faulting, because the magma intrusion causes ductile deformation instead of brittle failure.
3. Strike-slip faulting, as the two sides of the dike slide past each other.
4. Normal faulting, due to localized extension as the crust is pushed apart by the dike. (correct answer)

Explanation: When analyzing volcanic processes, you need to understand how magma intrusions create stress in the surrounding rock. A dike is a sheet-like intrusion that cuts vertically through existing rock layers, literally forcing the crust apart as it propagates upward. As the dike intrudes, it creates a localized zone of extension directly above it. Think of it like inserting a wedge into a crack – the material on either side must move apart to accommodate the new volume. This extensional stress causes the overlying rock to stretch and thin, leading to normal faulting where one block drops down relative to another along inclined fault planes. The surface expression would show parallel normal faults running along the same orientation as the dike below. Option A is incorrect because reverse faulting occurs under compression, not the extension created by dike intrusion. While magma does exert pressure, the dominant effect is pulling the crust apart, not squeezing it together. Option B misunderstands the brittle nature of shallow crustal rocks. Even though deeper rocks may deform ductilely, the upper crust typically responds to dike intrusion with brittle fracturing and faulting. Option C incorrectly suggests strike-slip motion. While the sides of the dike do separate, they move apart perpendicular to the dike walls, not parallel to them as in strike-slip faulting. Remember this key principle: dike intrusions create extension perpendicular to their orientation, and extension in the brittle crust produces normal faults. Look for this pattern whenever volcanic processes involve vertical magma intrusions.