1.
Which one of the following statements regarding rock deformation and strength is correct?
Correct Answer
A. Rupture and plastic deformation occur when stresses exceed the elastic limit of a material.
Explanation
Rupture and plastic deformation occur when stresses exceed the elastic limit of a material. This means that when the stress applied to a rock exceeds its elastic limit, it will undergo rupture (breaking) or plastic deformation (permanent change in shape). This is because beyond the elastic limit, the rock is unable to return to its original shape and instead undergoes permanent changes.
2.
Which one of the following stress situations results in folding of flat-lying, sedimentary strata?
Correct Answer
A. Horizontally directed; compressive stresses
Explanation
Horizontally directed compressive stresses can cause folding of flat-lying, sedimentary strata. This is because compressive stresses push the rocks together, causing them to buckle and fold. In contrast, vertically directed extensional or stretching stresses would cause the rocks to pull apart or stretch, which would not result in folding. Similarly, horizontally directed extensional stresses would cause the rocks to move apart horizontally, also not resulting in folding. Vertically directed compressional stresses would push the rocks down, but not cause folding. Therefore, the correct answer is horizontally directed compressive stresses.
3.
Which one of the following is consistent with deformation by folding?
Correct Answer
A. Horizontal distance is shortened perpendicular to fold axes.
Explanation
When rocks undergo deformation by folding, the layers of rock are bent and folded. As a result, the horizontal distance perpendicular to the fold axes is shortened. This is because the layers are compressed and pushed together, causing them to become closer and reducing the horizontal distance between them. Therefore, the statement "Horizontal distance is shortened perpendicular to fold axes" is consistent with deformation by folding.
4.
Which one of the following is true for anticlines but not for synclines?
Correct Answer
C. The deeper strata are buckled upward along the fold axis.
Explanation
This statement is true for anticlines but not for synclines. Anticlines are folds in rock layers where the deeper strata are pushed upward along the fold axis, creating an arch-like shape. In contrast, synclines are folds where the deeper strata are pushed downward along the fold axis, creating a trough-like shape. Therefore, the statement accurately describes a characteristic of anticlines that is not true for synclines.
5.
A deeply eroded, structural basin would exhibit ________.
Correct Answer
B. Strata oriented in roughly circular, outcrop patterns
Explanation
A deeply eroded, structural basin would exhibit strata oriented in roughly circular, outcrop patterns because as the basin erodes over time, the layers of rock are exposed at the surface. The circular pattern is a result of the erosion occurring from the center of the basin outward, causing the layers to be exposed in a circular shape. This can be seen in many structural basins where the layers of rock are visible in a circular or semi-circular pattern.
6.
A ________ fault has little or no vertical movements of the two blocks.
Correct Answer
C. Strike slip
Explanation
A strike-slip fault is characterized by horizontal movement along the fault plane, with little to no vertical displacement of the two blocks. In this type of fault, the rocks on either side of the fault slide past each other horizontally. This can occur due to shear stress causing the rocks to move in opposite directions along the fault line.
7.
In a ________ fault, the hanging wall block move up with respect to the footwall block.
Correct Answer
B. Inverse
Explanation
In an inverse fault, the hanging wall block moves up with respect to the footwall block. This type of fault occurs when the compressional forces cause the hanging wall block to move vertically upwards relative to the footwall block. It is commonly associated with convergent plate boundaries where two tectonic plates are colliding, resulting in compression and the uplifting of the hanging wall block.
8.
In thrust faulting, ________.
Correct Answer
B. The crust is shortened and thickened
Explanation
In thrust faulting, the crust is shortened and thickened. This occurs when two blocks of rock are pushed together, causing the rocks to buckle and fold. As the rocks are compressed, they become shorter and thicker. This type of faulting is commonly associated with convergent plate boundaries, where two tectonic plates are colliding. The compression forces cause the rocks to deform and create thrust faults, where one block of rock is pushed up and over the other. This results in the crust being shortened and thickened in the area of the fault.
9.
Which one of the following would not be a characteristic of the San Andreas fault zone?
Correct Answer
A. Steep, near vertical, dip-slip, fault scarps
Explanation
The San Andreas fault zone is known for its characteristic of steep, near vertical, dip-slip fault scarps. This means that the fault line has a steep angle and the movement along the fault is predominantly vertical. This characteristic is not found in sag ponds, deformed bedrock, or laterally offset stream channels, which are other features commonly associated with the San Andreas fault zone.
10.
A graben is characterized by ________.
Correct Answer
C. A hanging wall block that has moved down between two normal faults
Explanation
A graben is a type of geological formation that is characterized by a hanging wall block that has moved down between two normal faults. In this type of faulting, the crust is stretched and pulled apart, causing the hanging wall block to drop down relative to the footwall block. This creates a depressed area or trough-like structure, with the hanging wall block forming the lower part of the graben. This movement is opposite to that of a reverse fault, where the hanging wall block moves up relative to the footwall block.
11.
The mountains and valleys of the Basin and Range Province of the western United States formed in response to ________.
Correct Answer
C. Tensional stresses and normal-fault movements
Explanation
The mountains and valleys of the Basin and Range Province in the western United States formed due to tensional stresses and normal-fault movements. Tensional stresses occur when forces pull apart the Earth's crust, causing it to stretch and thin. This stretching leads to the formation of normal faults, where one block of the crust moves down relative to the other. Over time, repeated movement along these faults results in the uplift of mountain ranges and the formation of valleys in between.
12.
The Navajo and Dakota Sandstones are ________.
Correct Answer
B. Mesozoic, sedimentary rock formations in Utah, Colorado, and neighboring states
Explanation
The Navajo and Dakota Sandstones are Mesozoic, sedimentary rock formations in Utah, Colorado, and neighboring states.
13.
A ________ is a defined, recognizable, mappable, rock unit with a known age.
Correct Answer
C. Formation
Explanation
A formation is a defined, recognizable, mappable, rock unit with a known age. It refers to a distinct layer or group of layers of rock that have similar characteristics and were formed under similar geological conditions. Formations are important in stratigraphy, the study of rock layers and their relationships, as they help geologists understand the history and evolution of the Earth's crust.
14.
In a normal fault ________.
Correct Answer
C. The hanging wall block above an inclined fault plane moves downward relative to the other block
Explanation
In a normal fault, the hanging wall block above an inclined fault plane moves downward relative to the other block. This occurs because tension forces cause the hanging wall to move downward, creating a gap between the two blocks. This type of faulting is commonly associated with extensional tectonic forces, where the Earth's crust is being pulled apart. As the hanging wall moves downward, it creates a fault scarp or cliff on the surface.
15.
A reverse fault is one in which ________.
Correct Answer
A. The hanging wall block has moved up relative to the footwall block along an inclined fault
Explanation
A reverse fault is a type of fault where the hanging wall block moves up relative to the footwall block along an inclined fault. In this type of fault, the rocks on one side of the fault plane are pushed vertically upwards, causing the hanging wall block to move up relative to the footwall block. This movement is typically caused by compressional forces in the Earth's crust, which cause the rocks to be pushed together and uplifted. This is in contrast to a normal fault, where the hanging wall block moves down relative to the footwall block.
16.
Jointing in rocks is characterized by ________.
Correct Answer
D. Roughly parallel fractures separating blocks that show no displacement
Explanation
The correct answer is "roughly parallel fractures separating blocks that show no displacement." This explanation refers to jointing in rocks, which is characterized by fractures that occur without any movement or displacement of the rock blocks. These fractures are roughly parallel to each other and can be seen as cracks or fractures in the rock, but they do not result in any movement or offset of the rock blocks.
17.
________ are the products of horizontally directed, tensional stresses.
Correct Answer
A. Normal faults
Explanation
Normal faults are the products of horizontally directed, tensional stresses. In a normal fault, the hanging wall moves downward relative to the footwall. This type of faulting occurs when the Earth's crust is being pulled apart, causing the rocks to fracture and slide along the fault plane. The tensional stresses create a gap or space between the two sides of the fault, resulting in the hanging wall moving downward.
18.
________ in layered sedimentary rocks are evidence for horizontal compression and shortening.
Correct Answer
D. Tight folds
Explanation
Tight folds in layered sedimentary rocks are evidence for horizontal compression and shortening because they are formed when layers of rock are bent and deformed due to tectonic forces. This compression causes the rock layers to fold tightly, creating a series of folds that can be observed in the sedimentary rock. The presence of tight folds indicates that there has been horizontal compression and shortening in the rock formation.
19.
A transform fault is ________.
Correct Answer
A. A strike-slip fault that forms the boundary between tectonic plates
Explanation
A transform fault is a strike-slip fault that forms the boundary between tectonic plates. This means that it is a type of fault where the rocks on either side of the fault move horizontally past each other. Transform faults are commonly found along the boundaries of tectonic plates, such as the San Andreas Fault in California. They are characterized by the absence of vertical movement, unlike dip-slip faults where one side of the fault moves up or down relative to the other side. Transform faults play a significant role in plate tectonics and are responsible for the majority of earthquakes around the world.
20.
The ________ in California is the boundary between the North American and Pacific plates.
Correct Answer
B. San Andreas strike-slip fault
Explanation
The San Andreas strike-slip fault in California is the boundary between the North American and Pacific plates. This fault is known for its horizontal movement, where the rocks on either side of the fault slide past each other horizontally. This fault is responsible for numerous earthquakes in California and is a prominent feature of the tectonic activity in the region.
21.
Brittle deformation would be favored over plastic deformation in which of the following conditions?
Correct Answer
C. Cooler temperatures
Explanation
Brittle deformation is favored over plastic deformation in cooler temperatures because at lower temperatures, rocks become more rigid and less ductile. This means that they are more likely to fracture and break rather than undergo plastic deformation and flow. In contrast, warmer temperatures increase the ductility of rocks, making them more prone to plastic deformation. Therefore, cooler temperatures promote brittle deformation.
22.
A thrust fault is best described as ________.
Correct Answer
B. A low-angle, reverse fault
Explanation
A thrust fault is a type of reverse fault where the fault plane dips at a low angle (
23.
A ________ is a prominent ridge formed by differential erosion of tilted, alternating hard and soft strata.
Correct Answer
C. Hogback
Explanation
A hogback is a prominent ridge formed by differential erosion of tilted, alternating hard and soft strata. This means that the ridge is created when layers of rock with different hardness are eroded at different rates, resulting in a ridge-like formation. The term "hogback" is commonly used to describe this type of ridge.
24.
A horst is ________.
Correct Answer
A. An uplifted block bounded by two normal faults
Explanation
A horst is an uplifted block bounded by two normal faults. In geology, normal faults occur when there is tensional stress, causing the hanging wall to move downward relative to the footwall. In the case of a horst, the central block is uplifted between two normal faults, creating a raised area compared to the surrounding rock layers. This is in contrast to a graben, which is a downdropped block bounded by two normal faults.
25.
Which one of the following best describes the geology of the Black Hills region in South Dakota?
Correct Answer
D. An elongate dome cored by Proterozoic igneous and metamorpHic rocks
Explanation
The geology of the Black Hills region in South Dakota is best described as an elongate dome cored by Proterozoic igneous and metamorphic rocks. This means that the region is characterized by a dome-like structure, with the core composed of older igneous and metamorphic rocks from the Proterozoic era. This geologic formation has likely been exposed through erosion over time.
26.
The Great Rift Valley of East Africa is characterized by ________.
Correct Answer
C. Mainly normal faulting as East Africa begins to fragment
Explanation
The Great Rift Valley of East Africa is characterized by mainly normal faulting as East Africa begins to fragment. This means that the Earth's crust in this region is experiencing tensional forces that are causing it to break apart along vertical faults. As the crust separates, it creates a rift valley with steep walls and a flat floor. This process is associated with the gradual splitting of the African continent into two separate tectonic plates.
27.
The Michigan geologic map shows older, Paleozoic strata (in roughly circular patterns) surrounding a core area of Pennsylvanian rocks. What is this structure?
Correct Answer
D. Basin
Explanation
The Michigan geologic map shows older, Paleozoic strata (in roughly circular patterns) surrounding a core area of Pennsylvanian rocks. This structure is a basin because it is characterized by the circular pattern of older rocks surrounding a central core of younger rocks. A basin is a geological formation where the rock layers dip towards a central point, creating a bowl-like shape. The circular pattern of older rocks suggests that they were deposited in a basin, with the central core of Pennsylvanian rocks being the youngest layers.
28.
Normal and reverse faults are characterized mainly by ________.
Correct Answer
C. Dip slip
Explanation
Normal and reverse faults are characterized mainly by dip slip. Dip slip refers to the vertical movement of rock blocks along the fault plane. In a normal fault, the hanging wall moves downward relative to the footwall, while in a reverse fault, the hanging wall moves upward relative to the footwall. Both types of faults involve vertical displacement, which is why dip slip is the correct answer.
29.
A syncline is ________.
Correct Answer
C. A fold in which the strata dip toward the axis
Explanation
A syncline is a fold in which the strata dip toward the axis. This means that the layers of rock or sediment are sloping downward towards the center of the fold. This is in contrast to an anticline, where the strata dip away from the axis. In a syncline, the layers are typically curved downward, creating a U-shaped fold.
30.
Normal faults form in response to horizontal, tensional stresses that stretch or elongate the rocks.
Correct Answer
A. True
Explanation
Normal faults form in response to horizontal, tensional stresses that stretch or elongate the rocks. This means that when the rocks are being pulled apart, one side of the fault moves downward relative to the other side. This creates a gap or space between the rocks, which is known as a normal fault. Therefore, the statement "Normal faults form in response to horizontal, tensional stresses that stretch or elongate the rocks" is true.
31.
In a reverse fault, the hanging wall block moves up relative to the footwall block.
Correct Answer
A. True
Explanation
In a reverse fault, the hanging wall block moves up relative to the footwall block. This means that the block of rock above the fault plane moves in an upward direction compared to the block of rock below the fault plane. This movement is caused by compressional forces in the Earth's crust, which push the rocks together and cause them to deform. Reverse faults are commonly associated with convergent plate boundaries, where tectonic plates collide and push against each other.
32.
The oldest, sedimentary rock strata are exposed along the axial parts of deeply eroded anticlines.
Correct Answer
A. True
Explanation
The statement is true because the oldest sedimentary rock strata are typically found in the axial parts of deeply eroded anticlines. This is because anticlines are folds in the Earth's crust that form an arch-like shape, and erosion over time can expose the underlying layers of rock. As the oldest layers are typically deeper within the Earth, they are more likely to be exposed along the axial parts of these anticlines.
33.
Horizontal, compressive deformation involves shortening and thickening of the crust.
Correct Answer
A. True
Explanation
Horizontal, compressive deformation refers to the process in which the Earth's crust is shortened and thickened. This occurs when two tectonic plates collide or when compressive forces act on the crust. As a result of this deformation, the crust is compressed horizontally, causing it to shorten and become thicker. Therefore, the given statement that horizontal, compressive deformation involves shortening and thickening of the crust is true.
34.
Along oblique-slip faults, both blocks have horizontal and vertical components of movement.
Correct Answer
A. True
Explanation
Along oblique-slip faults, both blocks have horizontal and vertical components of movement. This means that the blocks move both horizontally and vertically along the fault plane. This is in contrast to other types of faults, such as normal faults or reverse faults, where the movement is predominantly vertical or horizontal, respectively. Oblique-slip faults are characterized by a combination of both horizontal and vertical movement, making the statement true.
35.
Basin and range topography, like that in the western and southwestern United States, indicates that compressive folding is active today or was active very recently, geologically speaking.
Correct Answer
B. False
Explanation
Basin and range topography, characterized by alternating mountain ranges and valleys, is actually indicative of tensional forces and normal faulting, rather than compressive folding. This type of topography is associated with the stretching and thinning of the Earth's crust, leading to the formation of fault blocks and basins. Therefore, the statement that basin and range topography indicates active or recent compressive folding is false.
36.
Plastic deformation occurs more readily in warm rock than in cool rock.
Correct Answer
A. True
Explanation
Plastic deformation occurs more readily in warm rock than in cool rock because higher temperatures increase the mobility of atoms and allow for easier movement of dislocations within the crystal lattice. This increased mobility facilitates the flow and rearrangement of the rock's structure, resulting in plastic deformation. In contrast, cool rock has lower atomic mobility, making it more resistant to plastic deformation. Therefore, warm rock is more likely to undergo plastic deformation compared to cool rock.
37.
A graben is an upraised block bounded by two reverse faults.
Correct Answer
B. False
Explanation
A graben is actually a down-dropped block bounded by two normal faults, not reverse faults. In a graben, the hanging wall moves downward relative to the footwall, creating a depressed area between the faults. This is in contrast to a horst, which is an upraised block bounded by normal faults. Therefore, the correct answer is false.
38.
Fractures in rock that have not involved any fault slippage are called joints.
Correct Answer
A. True
Explanation
Joints are fractures in rock that have not involved any fault slippage. This means that the rock has cracked or broken, but the two sides of the fracture have not moved relative to each other. Joints can form due to various geological processes such as cooling and contraction, tectonic stresses, or erosion. They can be important for groundwater flow, as well as for the formation of mineral deposits. Therefore, the statement that fractures in rock that have not involved any fault slippage are called joints is true.