Clastic Sedimentology And Petrography-test 1
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Questions and Answers
- 1.
Choose the best answer to suite Box E.
- A.
Upper flat bed
- B.
Ripples
- C.
Sub aqueous dune
- D.
Lower flat bed
Correct Answer
C. Sub aqueous duneExplanation
The best answer to suit Box E is "Sub aqueous dune". This is because a subaqueous dune refers to a sand formation that occurs underwater, typically in rivers, lakes, or oceans. It is characterized by the accumulation of sediment in a mound-like shape due to the action of water currents. Based on the given options, a subaqueous dune is the most suitable answer to describe the feature in Box E.Rate this question:
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- 2.
Gravity is the simplest mechanism of sediment transport.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Gravity is the simplest mechanism of sediment transport because it is always present and does not require any external force or energy input. Sediments, such as sand or rocks, naturally move downhill due to the force of gravity. This process is known as gravity-driven or gravitational sediment transport. It is a fundamental process in shaping the Earth's surface, as sediments are continuously transported by gravity in various forms, such as landslides, rivers, and glaciers. Therefore, it can be concluded that gravity is indeed the simplest mechanism of sediment transport.Rate this question:
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- 3.
Material may be carried in water tenth or hundreds of kilometers before being deposited.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Material may be carried in water for long distances before being deposited. This is true as water bodies like rivers, streams, and ocean currents can transport sediments, debris, and pollutants over vast distances. These materials can travel for tens or even hundreds of kilometers before settling down or being deposited in new locations. Therefore, the given statement is false.Rate this question:
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- 4.
When there is a very high concentration of sediment in water the mixture forms a debris flow, which can be thought of as a slurry with a consistency similar to that of dry concrete.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
When there is a very high concentration of sediment in water, the mixture forms a turbidity current, not a debris flow. A turbidity current is a fast-moving current of sediment-laden water flowing down a slope, while a debris flow is a fast-moving mixture of rocks, sediment, and water. Therefore, the statement that the mixture forms a debris flow with a consistency similar to that of dry concrete is false.Rate this question:
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- 5.
Flows can be assigned a parameter called a .
Correct Answer
Reynolds numberExplanation
The parameter that can be assigned to flows is called the Reynolds number.Rate this question:
- 6.
: The clasts move by rolling along at the bottom of the air or water flow without losing contact with the bed surface.
Correct Answer
RollingExplanation
The correct answer is "Rolling" because when clasts move by rolling, they maintain contact with the bed surface and are not lifted off or suspended in the air or water flow. This method of movement is common for larger and rounder particles that can easily roll along the bottom due to the force of the flow. Rolling is a form of sediment transport that occurs in rivers, streams, and other water bodies, as well as in wind-driven environments.Rate this question:
- 7.
The effect can best be explained by considering flow of a fluid (air,water, or any fluid medium) in a tube that is narrower at one end than the other.
Correct Answer
BernoulliExplanation
The Bernoulli principle states that as the speed of a fluid increases, its pressure decreases. This can be observed in the flow of a fluid in a tube that is narrower at one end than the other. As the fluid flows through the narrow section, its speed increases, causing the pressure to decrease. This principle is important in various applications, such as in the design of aircraft wings and the operation of Venturi meters.Rate this question:
- 8.
A is a morphological feature formed by the interaction between a flow and cohesionless sediment on a bed.
Correct Answer
bedformExplanation
A bedform is a morphological feature formed by the interaction between a flow and cohesionless sediment on a bed. This means that when a fluid, such as water or air, flows over sediment that lacks cohesion (particles are not bound together), it can create different shapes and patterns on the bed. These bedforms can include ripples, dunes, or even larger features like sand waves. The interaction between the flow and sediment causes the sediment to be transported and rearranged, resulting in the formation of distinct bedforms.Rate this question:
- 9.
Fill up the missing sections accordingly: Box A is .
Correct Answer
Windward slope - 10.
Fill up the missing sections accordingly: Box B is .
Correct Answer
Leeward slope - 11.
Fill up the missing sections accordingly: Box C is .
Correct Answer
Slipface - 12.
Fill up the missing sections accordingly: Box D is .
Correct Answer
Apron - 13.
Avalanching of grains occurs down the downstream or stoss side of the ripple as accumulated grains become unstable at the crest.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because avalanching of grains actually occurs on the upstream or lee side of the ripple, not the downstream or stoss side. This is because as grains accumulate on the upstream side, they become unstable and slide down the slope, causing the ripple to move in the downstream direction.Rate this question:
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- 14.
What is the possible sedimentary structure for box A.
Correct Answer
Planar cross bedsExplanation
Planar cross beds are a type of sedimentary structure characterized by inclined layers of sediment within a larger layer. These inclined layers are formed by the migration of sediment in response to the flow of a current or wind. The layers are typically planar and can be seen as distinct cross-cutting lines within the sedimentary rock. This structure is commonly found in environments such as river channels, dunes, or tidal flats, where the movement of water or wind causes the deposition of sediment in inclined layers. Therefore, box A likely exhibits planar cross beds as a result of sediment deposition in a dynamic environment.Rate this question:
- 15.
What is the possible sedimentary structure for box B.
Correct Answer
Trough cross bedsExplanation
Trough cross beds are a type of sedimentary structure that form when sediment is deposited in a trough-like shape due to the action of currents or waves. This structure is commonly found in environments such as river channels or beach deposits where there is a dominant direction of flow. The sediment is deposited in inclined layers that dip in the direction of the current, creating a distinctive trough shape. This type of structure can provide valuable information about the direction and intensity of ancient currents or waves in a sedimentary environment.Rate this question:
- 16.
The formation of current ripples require smoderate flow velocities over a hydrodynamically rough bed.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Current ripples are formed by the interaction of water flow with a sediment bed. They are typically found in environments with low to moderate flow velocities. Hydrodynamically rough beds, on the other hand, are characterized by larger sediment particles that create turbulent flow conditions. These conditions are not conducive to the formation of current ripples. Therefore, the statement is false.Rate this question:
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- 17.
Trough cross bedding formed by the migration of sinuous subaqueous dunes typically has asymptotic bottom contacts and an undulating lower boundary.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
This statement is true because trough cross bedding formed by the migration of sinuous subaqueous dunes indeed typically has asymptotic bottom contacts and an undulating lower boundary. This means that the layers of sediment within the troughs of these dunes are inclined at an angle and have a smooth, curved shape at the bottom. This is a characteristic feature of cross bedding formed by the movement of dunes underwater.Rate this question:
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- 18.
Bars can be made up of sandy sediment , or mixtures of coarse grain sizes.
Correct Answer
gravelly materialExplanation
The given statement suggests that bars can be composed of sandy sediment or mixtures of coarse grain sizes. The term "gravelly material" refers to a mixture of coarse grains, which aligns with the statement. Therefore, gravelly material is a suitable explanation for the given answer.Rate this question:
- 19.
Plane beds form in coarser sands at relatively high flow velocities.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Plane beds do not form in coarser sands at relatively high flow velocities. Plane beds are typically formed in finer sands or silts at low flow velocities. In coarser sands, bedforms such as ripples or dunes are more likely to form. Therefore, the statement is false.Rate this question:
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- 20.
Antidune cross-bedding would be stratification dipping upstream.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Antidune cross-bedding refers to the formation of sedimentary layers that dip upstream. This means that the layers of sediment are inclined in the opposite direction of the water flow. This phenomenon occurs in fast-flowing water, such as in rivers or streams, where the velocity of the water is high enough to create small-scale sand dunes. As the water flows over these dunes, it causes the sediment to be deposited in inclined layers, with the dip direction being opposite to the flow direction. Therefore, the statement "Antidune cross-bedding would be stratification dipping upstream" is true.Rate this question:
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- 21.
Choose the best answer to suite Box A.
- A.
Upper flat bed
- B.
Ripples
- C.
Sub aqueous dune
- D.
Lower flat bed
Correct Answer
A. Upper flat bedExplanation
The correct answer is "Upper flat bed" because it is the most suitable option to fill in Box A. The other options, such as "Ripples," "Sub aqueous dune," and "Lower flat bed," do not make sense in the given context. Therefore, "Upper flat bed" is the best answer.Rate this question:
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- 22.
Choose the best answer to suite Box D.
- A.
Upper flat bed
- B.
Ripples
- C.
Sub aqueous dune
- D.
Lower flat bed
Correct Answer
B. RipplesExplanation
The best answer to suit Box D is "Ripples" because ripples are typically found in shallow water environments and are characterized by small wave-like formations on the sediment surface. This suggests that Box D represents a shallow water environment where ripples are present. The other options, such as Upper flat bed, Sub aqueous dune, and Lower flat bed, do not specifically indicate a shallow water environment or the presence of ripples.Rate this question:
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- 23.
The height and energy of waves is determined by the strength of the wind and the , the expanse of water across which the wave-generating wind blows.
Correct Answer
fetchExplanation
The height and energy of waves is determined by the strength of the wind and the fetch, which refers to the expanse of water across which the wave-generating wind blows. The fetch is an important factor because it determines the distance over which the wind can act on the water surface, allowing the waves to build up and gain energy. A longer fetch allows the wind to generate larger and more powerful waves, while a shorter fetch results in smaller and less energetic waves. Therefore, the fetch plays a crucial role in determining the characteristics of waves.Rate this question:
- 24.
The depth to which surface waves affect a water body is referred to as the .
Correct Answer
wave baseExplanation
The depth to which surface waves affect a water body is referred to as the wave base. This term is used to describe the point at which the wave energy dissipates and the water becomes still. The wave base is determined by factors such as wave height, wavelength, and water depth. It is an important concept in understanding the behavior and impact of waves on a water body.Rate this question:
- 25.
In plan view wave ripples have long, straight to gently sinuous crests which may bifurcate (split) these characteristics may be seen on the bedding planes of sedimentary rocks.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
The statement is true because wave ripples in plan view do indeed have long, straight to gently sinuous crests that can bifurcate. These characteristics can be observed on the bedding planes of sedimentary rocks.Rate this question:
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- 26.
Wave ripples can form in any ohesive sediment and are principally seen in coarse silts and sand of all grades.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Wave ripples can form in any cohesive sediment, including fine silts and clays, as well as in sand of all grades. Therefore, the statement that wave ripples are principally seen in coarse silts and sand of all grades is incorrect.Rate this question:
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- 27.
Wave ripples are formed only in relatively shallow water in the absence of strong currents, whereas current ripples may form as a result of water flow in any depth in any subaqueous environment.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
This statement is true because wave ripples are specifically formed in shallow water and require the absence of strong currents. On the other hand, current ripples can form in any depth of water and in any subaqueous environment as a result of water flow. Therefore, the statement accurately distinguishes between wave ripples and current ripples, making the answer true.Rate this question:
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- 28.
The deposits of debris flows on land are typically conglomerates although clast- supported deposits also occur if the relative proportion of large clasts is high in the sediment mixture.
Correct Answer
matrix supported, matrix-supportedExplanation
The correct answer is "matrix supported, matrix-supported". This means that the deposits of debris flows on land are typically composed of conglomerates, where the matrix material supports the clasts. However, in some cases, clast-supported deposits can also occur if there is a high proportion of large clasts in the sediment mixture.Rate this question:
- 29.
Turbidity currents are gravity-driven turbid mixtures of sediment temporarily suspended in water.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Turbidity currents are indeed gravity-driven turbid mixtures of sediment temporarily suspended in water. This means that the currents are caused by the force of gravity, which causes sediments to become suspended in water, creating a turbid mixture.Rate this question:
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- 30.
Turbidity currents are waning flows, that is,they decrease velocity through time as they deposit material,but this means that they also decrease velocity with distance from the source.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Turbidity currents are sediment-laden flows that gradually slow down and deposit material over time. As they deposit material, their velocity decreases, which also means that their velocity decreases as they travel further away from the source. Therefore, the statement is true.Rate this question:
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- 31.
Complete Ta–e Bouma sequences are in fact rather common.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement suggests that complete Ta-e Bouma sequences are common. However, the correct answer is false, indicating that complete Ta-e Bouma sequences are not actually common.Rate this question:
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- 32.
High-density turbidity currents have a bulk density of at least gcm-3.
Correct Answer
1.1Explanation
High-density turbidity currents have a bulk density of at least 1.1 g/cm3. This means that the particles and sediment within the turbidity current are densely packed together, resulting in a higher overall density. This high density allows the turbidity current to flow more rapidly and with greater force, carrying larger particles and causing more erosion and deposition. The high density also contributes to the ability of the turbidity current to travel long distances and maintain its flow over time.Rate this question:
- 33.
A is a type of sediment- gravity flow in which the supporting fluid, which can be either air or water, acts only as a lubricant, and grains within the flow remain in suspension due to grain-to-grain collisions that generate a dispersive pressure to prevent further settling.
Correct Answer
grain flowExplanation
Grain flow is a type of sediment gravity flow where the supporting fluid, such as air or water, acts as a lubricant and the grains within the flow remain suspended due to grain-to-grain collisions. These collisions generate a dispersive pressure that prevents the grains from settling further. In other words, the grains are kept in suspension and do not settle due to the constant collisions and the pressure they generate. This phenomenon is known as grain flow.Rate this question:
- 34.
A is precipitated out of fluids as part of the post-depositional history of the sediment. It will normally be crystal line material that fills,or partly fills,the gaps between the grains.
Correct Answer
cementExplanation
Cement is a substance that is precipitated out of fluids during the post-depositional history of sediment. It typically forms as a crystalline material that fills or partially fills the gaps between the grains of sediment. This process helps to bind the sediment particles together, forming a solid rock-like structure.Rate this question:
- 35.
When clay-and silt-sized particles are mixed in unknown proportions as the main constituents in unconsolidated sediment we would call this material .
Correct Answer
mudExplanation
When clay and silt-sized particles are mixed in unknown proportions as the main constituents in unconsolidated sediment, the resulting material is called mud.Rate this question:
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