content eq2 Flashcards
1
Q
A
2
Q
How is a wave generated?
A
Waves are generated by friction between the wind and the water surface, transferring wind energy into the water and forming ripples that develop into waves.
3
Q
What is the movement of water particles in a wave?
A
Water particles in a wave move in circular orbits, transferring energy from one particle to the next, while the net horizontal movement of water is negligible.
4
Q
How does water depth affect the wave particle orbit?
A
The size of the orbital motion decreases with depth, meaning that at greater depths, the movement of water particles is less pronounced.
5
Q
Define wave height, wavelength, and wave frequency.
A
Wave height is the vertical distance from the crest to the trough; wavelength is the horizontal distance between two consecutive crests (or troughs); wave frequency is the number of waves passing a given point per unit time.
6
Q
What happens to waves in the open sea?
A
In the open sea, waves are energy moving through water. Although water particles follow an orbital motion, there is no net horizontal water transport.
7
Q
What factors influence the size of a wave?
A
Wave size depends on wind strength, wind duration, water depth, and wave fetch—the uninterrupted distance over which the wind blows.
8
Q
What is ‘wave fetch’?
A
Wave fetch is the distance over open water that the wind blows uninterrupted, allowing waves to gather energy and grow in size.
9
Q
Describe the process of wave breaking.
A
As waves approach the shore, when the water depth is about half the wavelength, the orbital motion of particles is affected by the seabed. Friction distorts their circular motion into elliptical paths, slowing the wave, shortening its wavelength, increasing its height, and ultimately causing the crest to topple forward.
10
Q
What are swash and backwash?
A
Swash is the forward movement of water up the beach after a wave breaks, and backwash is the return flow of water down the beach due to gravity.
11
Q
What characterises constructive waves?
A
Constructive waves are low-energy with low, flat wave heights (<1 m), long wavelengths (up to 100 m), and low frequency (6–9 per minute). They have a strong swash that transports sediment up the beach and a weaker backwash that allows sediment deposition, forming a berm at the high tide line.
12
Q
How do constructive waves affect beach morphology?
A
They result in net sediment movement up the beach, steepening the beach profile, forming berms, and sorting sediments—larger particles remain in the back while finer sands are deposited closer to the sea.
13
Q
What are the characteristics of destructive waves?
A
Destructive waves are high-energy with large wave heights (>1 m), short wavelengths (around 20 m), and high frequency (13–15 per minute). Their weak swash and strong backwash result in net sediment movement down the beach, eroding the upper parts and depositing coarse materials offshore.
14
Q
How do destructive waves influence beach sediment profiles?
A
They reduce the beach gradient by transporting sediment down the beach, forming features such as offshore ridges or berms from coarse, pebble-sized materials, while friction may cause sorting with finer materials nearer the sea.
15
Q
What is beach morphology?
A
Beach morphology refers to the shape and structure of the beach, including features like berms, ridges, and the overall slope of the sediment profile.
16
Q
How do seasonal variations affect wave types and beach profiles in the UK?
A
In winter, destructive, high-energy waves dominate, flattening the beach profile and spreading shingle across the beach; in summer, constructive, low-energy waves prevail, steepening the beach and sorting sediments to form berms at the high tide line.
17
Q
What are decadal variations in coastal morphology linked to?
A
Decadal variations are linked to climate change, with more extreme weather events potentially extending winter profiles, increasing the frequency of destructive waves, reducing beach sizes, and allowing tides to reach further inland.
18
Q
How do monthly variations in tide height influence beach morphology?
A
Monthly changes in tidal range—from high spring tides to low neap tides—lead to the formation and successive destruction of berms as the swash reaches progressively lower down the beach.
19
Q
How can daily variations alter beach profiles?
A
Storm events can rapidly produce destructive waves that reshape the beach within hours, while calm conditions may allow constructive waves to rebuild the profile over a few days.
20
Q
Differentiate between sea waves and swell waves.
A
Sea waves are generated by local winds and can vary in height and direction; when the wind drops, the residual energy travels as swell waves, which can absorb local sea waves, travel long distances, and impact the coast even in the absence of local wind.
21
Q
What determines the energy transferred from the wind to the sea?
A
The energy transfer depends on wind strength, wind fetch (distance over which the wind blows), and wind duration—the longer and stronger the wind blows over an uninterrupted fetch, the more energy is imparted to the water.
22
Q
What are the four main wave erosion processes?
A
Hydraulic action, corrosion, abrasion (corrasion), and attrition.
23
Q
How are wave erosion processes influenced by wave type, size, and lithology?
A
They are most effective during high-energy storm events with large, destructive waves, and their impact varies with rock type—softer, unconsolidated sediments erode faster than hard, resistant rocks.
24
Q
Under what conditions do most wave erosion events occur in the UK?
A
Erosion mainly occurs in winter during high-energy storms, especially when the wind blows directly onshore and at high tide when deeper water minimizes friction losses.
25
How does hydraulic action erode a cliff?
Hydraulic action involves the force of water breaking rock: either by the direct impact of plunging waves or by compressing air into cracks, which then expands and forces the cracks open.
26
What magnitude of force can plunging destructive waves exert in hydraulic action?
They can exert a force of up to 50 kg per cm², sufficient to dislodge material from unconsolidated sediments or weak rocks.
27
Why is hydraulic action particularly significant for hard, resistant igneous rocks?
In hard rocks, hydraulic action may be the only effective erosion process, as it can exploit existing cooling joints to gradually break the rock apart.
28
What is abrasion (corrasion) and how does it work?
Abrasion occurs when waves pick up sediment (load items) and hurl them against the rock surface, chipping away at the rock until small fragments break off.
29
Under which conditions is abrasion most effective?
Abrasion is most effective during high-energy destructive wave events with large wave heights and when a supply of hard load items (e.g., shingle) is available near the cliff base.
30
Which rock types are most vulnerable to abrasion?
Soft sedimentary rocks such as chalk, mudstones, clays, and unconsolidated materials like boulder clay erode quickly by abrasion.
31
What is corrosion in the context of wave erosion?
Corrosion is the chemical dissolution of rock minerals by water in the waves, which removes minerals in solution and is enhanced by rainwater and sea spray.
32
Which type of waves favor corrosion and why?
Constructive waves favor corrosion because their slow, spilling nature prolongs the contact time between the water and the rock, allowing chemical reactions to occur more effectively.
33
What rock types erode most quickly by corrosion?
Carbonate rocks such as limestones (including chalk, Jurassic limestone, and Carboniferous limestone) and sedimentary rocks with calcite cement erode most quickly by corrosion.
34
What is attrition and how does it contribute to sediment modification?
Attrition is the erosion of sediment particles through collisions as they are transported by swash and backwash, breaking them into smaller particles and rounding off sharp edges.
35
Which rocks are most affected by attrition?
Soft rocks like poorly cemented sandstones, chalk, and clay are rapidly broken down by attrition into silt and sand, while even harder rocks like quartz and granite form rounded shingle pebbles.
36
What contrasting examples illustrate the effect of wave erosion on different lithologies?
The boulder clay of Holderness Coast in Yorkshire has retreated by 120 m in the last 100 years, while the granite of Land's End in Cornwall has only retreated by 10 cm in the same period, demonstrating how lithology influences erosion rates.
37
What is a wave-cut notch?
A curved indentation (about 1–2 m high) at the base of a cliff, formed between the high and low tide marks by destructive waves using hydraulic action, abrasion, and sometimes corrosion.
38
How does a wave-cut notch form?
Destructive waves erode the cliff base through hydraulic action (direct force and air compression in cracks), abrasion (load items chipping away the rock), and occasionally corrosion, creating a notch whose depth varies with rock resistance.
39
How does rock resistance affect notch depth?
Areas of softer or less resistant rock erode faster, resulting in deeper notches; conversely, harder sections create shallower notches along the cliff base.
40
What is a wave-cut platform?
A flat, rock surface exposed at low tide that forms when marine erosion deepens a notch until the overlying material collapses by mass movement, leaving the uneroded rock (always submerged at low tide) as a platform.
41
Describe the formation process of a wave-cut platform.
Marine erosion (via abrasion and hydraulic action) forms a notch along the cliff base; as the notch deepens, overlying rock collapses due to gravity (mass movement), causing the cliff to retreat (coastal recession) and exposing a flat platform at low tide.
42
What is the typical slope of a wave-cut platform?
They usually slope seaward at around 4 degrees.
43
How does weathering influence a wave-cut platform?
Weathering attacks weaknesses in the platform surface, forming indentations that become rock pools at low tide.
44
Why do wave-cut platforms rarely extend for more than a few hundred metres?
The shallow water over the platform causes waves to break and lose energy before reaching further out, limiting the platform’s extent.
45
How do cliffs form from wave erosion?
A wave-cut notch is eroded until overlying rock collapses by mass movement; the newly exposed, steep, and usually unvegetated rock face forms a cliff.
46
What is the cave-arch-stack-stump sequence?
A series of coastal landforms created along zones of weakness: a sea cave forms along joints/faults, which then deepens into an arch, eventually collapsing to leave a stack, and further erosion reduces the stack to a stump.
47
How do sea caves develop in this sequence?
Hydraulic action exploits joints, faults, or vertically dipping bedding planes, eroding a weak point into a sea cave, especially where wave refraction concentrates energy on headland sides.
48
How does a sea arch form from a sea cave?
When erosion along a continuous line of weakness on opposite sides of a headland causes two sea caves to extend and meet, they form a complete tunnel, or arch, through the headland.
49
What process leads to the formation of a stack?
Continued hydraulic action, abrasion, and weathering erode the sides and roof of a sea arch; the arch eventually collapses (blockfall), detaching the seaward portion as a vertical column known as a stack.
50
How is a stump formed from a stack?
Marine erosion (especially at the base) forms notches around the stack; repeated undercutting and collapse reduce the stack, leaving a smaller remnant called a stump, visible mostly at low tide.
51
Why don’t unconsolidated, soft sedimentary or metamorphic rocks form the cave-arch-stack-stump sequence?
They are not competent enough; such rocks erode too quickly or uniformly, preventing the development of distinct, long-lasting coastal features.
52
How does the dip of rock strata influence cliff slopes?
Horizontal, vertical, or landward dipping strata produce steep, nearly vertical cliffs, whereas seaward dipping strata or unconsolidated lithologies tend to form shallower slopes.
53
What happens on a wide platform regarding wave energy?
On a wide platform, waves break and the swash loses energy before reaching the cliff, which can halt or slow the rate of coastal recession.
54
Can you recall a mnemonic for the cave-arch-stack-stump sequence?
Yes—remember “C-A-S-S”: Cave, Arch, Stack, Stump, which outlines the progressive stages of coastal erosion.
55
What are the four main processes of sediment transportation?
Sediment is transported by traction, saltation, suspension, and solution.
56
Define traction in sediment transportation.
Traction involves large, heavy load items (e.g. boulders, cobbles, pebbles) being rolled along the sea bed by wave action and currents.
57
What is saltation and which sediment type is commonly transported by it?
Saltation is the bouncing or hopping movement of lighter sediment particles, typically sand, along the surface; it can occur by both wave and wind action.
58
How does suspension transport sediment?
Suspension carries very fine particles, such as silt or clay, aloft within the water column (or air), giving coastal waters a cloudy or muddy appearance.
59
Explain the process of solution in sediment transportation.
In solution, sediment is dissolved in the water and transported in a dissolved state, often affecting soluble minerals.
60
How does the angle of wave attack influence sediment transport?
The angle of wave attack determines the direction of sediment movement; when waves hit directly (90°) the material moves up and down the beach with no net lateral transport.
61
What happens when waves approach the coast at an angle?
When waves strike at an angle, the incoming swash transports sediment both up-beach and laterally, while the gravitational backwash moves it perpendicularly down the beach—producing net lateral transport known as longshore drift.
62
What is longshore drift?
Longshore drift is the net lateral movement of sediment along the coastline, created by the oblique angle of incoming swash and the perpendicular backwash, resulting in a zig-zag transport pattern along the beach.
63
Which wave angle produces the strongest longshore drift?
A wave angle of approximately 30° to the coastline produces the strongest longshore drift movement.
64
What role do prevailing winds play in sediment transport?
Prevailing winds determine the dominant wave direction, and hence the overall direction of longshore drift, though local features and wave refraction can modify this direction.
65
How do tidal currents influence sediment transportation?
Tidal currents, generated by the gravitational pull of the Moon and Sun, transport sediment in both the nearshore and offshore zones by moving water over various spatial and temporal scales.
66
What is the significance of rip currents in sediment transport?
Rip currents are narrow, fast-flowing channels that can transport sediment a few metres out to sea for several hours, especially when the wind is blowing directly onshore.
67
How does the process of longshore drift affect coastal sediment cells?
Sediment eroded from a source area is transported along the coast by longshore drift and deposited in a sink area, contributing to the sediment cell dynamics along the coastline.
68
How do tides affect the movement of sediment?
Tides cause regular changes in sea level that create tidal currents; these currents transport sediment across the foreshore and offshore, with tidal range and coastline shape influencing the strength of this transport.
69
What is a tidal range and what factors influence it?
Tidal range is the vertical distance between high tide and low tide. It is influenced by the distance from amphidromic points, coastline shape, and features like bays and estuaries which can amplify tidal flow.
70
How can a large tidal range influence sediment transport?
A large tidal range produces stronger tidal currents that can transport sediment more forcefully and even generate tidal bores in estuaries, which further enhance sediment movement.
71
What factors determine the strength and effectiveness of sediment transport by waves?
Key factors include the angle of wave attack, wave height and frequency, energy from wind (strength, duration, and fetch), and the lithology of the coastal sediments.
72
How does wave fetch influence sediment transportation?
Wave fetch—the uninterrupted distance over water that the wind blows—allows waves to gather more energy, which in turn increases the capacity of waves to transport sediment over longer distances.
73
Describe how currents contribute to sediment transport on different scales.
Currents can transport sediment on a variety of scales: global thermohaline circulation moves sediment between oceans over centuries, while localized rip currents and tidal flows move sediment on the order of meters to kilometers in hours or days.
74
What is the effect of wind on sediment transportation in the nearshore zone?
On dry, windy days, wind can cause saltation of sand particles, forming a layer of saltating sand 2–10 cm above the beach, enhancing sediment movement in addition to wave action.
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1. What is deposition in coastal environments?
Deposition is the process where sediment is laid down when waves, tides, or currents lose enough energy to transport it further.
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2. What factors can cause a loss of energy that leads to deposition?
A drop in wind strength, obstructions (such as groynes or headlands), energy dissipation by wave refraction, and friction from extended transport across shallow, angled nearshore areas.
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3. How does gravity settling work as a depositional process?
When water energy decreases, larger particles settle first and, as energy drops further, smaller sediments like sand and silt are deposited.
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4. What is flocculation and why is it important for deposition?
Flocculation is when very fine particles (e.g. clay) clump together through electrical or chemical attraction, becoming heavy enough to settle out of suspension.
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5. What materials primarily form beaches?
Beaches consist of accumulations of sand and/or shingle found in the foreshore and backshore zones.
80
6. How do constructive waves build beaches?
Constructive waves carry sediment up the beach with their strong swash, while a weaker backwash leaves material behind, gradually building a beach.
81
7. What defines a bayhead beach?
A bayhead beach is a curved beach at the back of a bay, formed by wave refraction dispersing energy around the bay perimeter, leading to focused deposition.
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8. How does wave refraction contribute to bayhead beach formation?
Wave refraction concentrates erosive energy on headlands and disperses it within the bay, so sediment is deposited in the bay rather than being uniformly eroded.
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9. What is a spit in coastal depositional landforms?
A spit is a linear ridge of sand or shingle extending from the coast into the sea, usually formed when longshore drift deposits sediment beyond a coastal turn.
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10. How does longshore drift contribute to spit formation?
Longshore drift moves sediment along the coastline; when the coast changes direction, the energy dissipates, and sediment accumulates to form a spit.
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11. What controls the length of a spit?
The length is determined by secondary currents—such as river flow or localized wave erosion—which can limit deposition at the distal end.
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12. What is a hooked or recurved spit?
A hooked (or recurved) spit is one whose end curves landward, often due to wave refraction or intermittent opposing currents that redirect sediment deposition.
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13. What factors can lead to the formation of a hooked spit?
Wave refraction around the spit’s end, opposing wind or wave directions, or strong incoming tidal currents can cause a spit to bend landward.
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14. What is a double spit?
A double spit consists of two spits extending from opposite sides of a bay toward the middle, formed by differing longshore drift directions.
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15. How can double spits form?
They form when opposing longshore drift directions operate on opposite sides of a bay or when rising sea levels drive onshore deposition from both ends.
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16. What are offshore bars (or breakpoint bars)?
Offshore bars are ridges of sand or shingle running parallel to the coast in the offshore zone, deposited where backwash ceases to move sediment further.
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17. How do offshore bars form?
They form from sediment eroded by destructive waves and carried seawards by backwash, then deposited at the boundary where orbital motion no longer reaches the seabed.
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18. What are some uses of offshore bars?
Offshore bars can be used for wind farm construction, as sources for beach nourishment, and for dredging shingle used in construction.
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19. What are bars and barrier beaches?
They are linear ridges of sand or shingle extending across a bay and connected to land on both sides, trapping seawater behind them to form lagoons.
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20. How do barrier beaches form on drift-aligned coastlines?
When longshore drift extends a spit completely across a bay, it traps water behind it and forms a continuous ridge known as a barrier beach.
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21. Give an example of a barrier beach.
The 9 km barrier beach across Start Bay in Devon, which traps seawater to form the Slapton Ley lagoon.
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22. What is a tombolo?
A tombolo is a linear deposit (or bar) of sand and shingle that connects an offshore island to the mainland.
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23. How does longshore drift contribute to tombolo formation?
Longshore drift builds a spit from the mainland that gradually connects with an offshore island, forming a tombolo.
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24. How can wave refraction lead to tombolo formation?
Wave refraction around both sides of an island can cause wave fronts to converge on the landward side, cancelling swash and allowing deposition between the island and mainland.
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25. What is a cuspate foreland?
A cuspate foreland is a low, triangular-shaped headland formed by the deposition of sediment where longshore drift currents from opposing directions converge.
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26. How does opposing longshore drift create a cuspate foreland?
When sediment is deposited simultaneously from two converging longshore drift currents, it forms a triangular accumulation extending seaward.
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27. What is a sediment cell in coastal systems?
A sediment cell is a dynamic system where sediment is eroded from a source area, transported along the coast (often by longshore drift), and deposited in a sink area.
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28. How does plant succession stabilize depositional landforms?
Plants stabilize these areas by binding loose sediment with their roots and reducing erosion through their foliage, which slows wind and water flow.
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29. What is psammosere?
Psammosere is the process of plant succession on sand dunes, leading to stabilization, soil formation, and further deposition.
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30. What is halosere?
Halosere is the process of plant succession in salt marshes, where halophytic plants colonize and stabilize the sediment.
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31. Why are depositional landforms considered inherently unstable?
They are composed of unconsolidated materials that are easily reworked by waves, tides, currents, and wind, making them dynamic and changeable.
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32. How does sediment from river systems influence coastal deposition?
Sediment delivered by rivers adds material to coastal areas, supplementing what is transported by marine processes, and contributes to deposition in deltas and along beaches.
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33. What role does wave refraction play in the deposition process?
Wave refraction dissipates wave energy, causing waves to break earlier and deposit sediment where energy is insufficient to continue transport.
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34. How does friction in shallow nearshore zones promote deposition?
Friction slows wave energy as waves travel across shallow, angled areas, reducing their ability to transport sediment and encouraging deposition.
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35. What is the relationship between wave energy loss and deposition?
When waves lose energy due to factors like reduced wind, obstructions, or friction, they can no longer carry sediment, resulting in its deposition.
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36. How can barrier islands form from barrier beaches?
Barrier islands form when a chain of barrier beaches emerges offshore, as continued deposition builds land masses that become detached from the mainland.
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37. What is the difference between swash-aligned and drift-aligned coastlines?
Swash-aligned coastlines face the prevailing wind directly, with wave fronts parallel to the coast, while drift-aligned coastlines are angled to the wind, promoting significant longshore drift.
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38. What characterizes swash-aligned beaches?
They typically have well-defined berms and little lateral sediment movement because the swash moves directly up and down the beach.
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39. What characterizes drift-aligned beaches?
Drift-aligned beaches exhibit strong longshore drift, linear stretches of sediment, and a sorting effect where finer particles are carried further along the coast.
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40. How do secondary currents affect the length of spits?
Secondary currents, such as river flows or localized wave action, can erode the distal end of a spit, limiting its extension until deposition and erosion reach equilibrium.
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41. How do bars and barrier beaches lead to lagoon formation?
They trap seawater behind the deposited ridge, creating an enclosed or semi-enclosed water body known as a lagoon.
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42. How can coastal management be influenced by plant succession on depositional landforms?
Coastal management may be needed when plant succession causes infilling of lagoons or significant changes in depositional patterns, as seen with Slapton Ley, where salt marsh succession threatens to transform the lagoon into a terrestrial ecosystem.
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1. What is a sediment cell (or littoral cell)?
It is a linked system of sources, transfers, and sinks of sediment along a section of coastline.
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2. What are the three main components of a sediment cell?
Inputs (sources), transfers, and outputs (sinks).
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3. Can you give an example of a sediment cell?
Yes – for instance, Flanborough Head acts as a source, the Holderness Coast as a transfer zone, and Spurn Head as a sink.
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4. How many primary sediment cells are there along the coast of England and Wales?
There are 11 primary sediment cells, each with sub-cells.
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5. What geographical features form the boundaries of sediment cells?
Major headlands or large estuaries.
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6. In what way is a sediment cell considered a closed system?
It operates with virtually no significant sediment input or output beyond its defined boundaries, maintaining internal circulation.
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7. What are 'inputs' in the context of a sediment cell?
They are the sources where sediment is generated or supplied to the cell.
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8. List some examples of sediment inputs.
Cliff erosion, onshore currents, river transport, wind-blown (aeolian) sediment, subaerial processes, marine organisms, and offshore bars.
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9. What does 'transfers' refer to in a sediment cell?
It refers to the movement of sediment along the coast via processes like longshore drift, swash, backwash, and tidal or ocean currents.
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10. Provide examples of sediment transfer processes.
Longshore drift, swash, backwash, tidal currents, sea/ocean currents, and wind-driven transport.
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11. What are 'sinks' in a sediment cell?
They are areas where sediment is deposited and accumulates, forming depositional landforms.
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12. What are some examples of depositional sinks?
Backshore depositional landforms (e.g. sand dunes), foreshore depositional landforms (e.g. beaches), nearshore landforms (e.g. bars), and offshore features (e.g. barrier islands).
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13. Define dynamic equilibrium in the context of sediment cells.
It is a state where sediment inputs from sources are balanced by deposition in sinks, yet there is a constant movement of sediment throughout the system.
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14. How is dynamic equilibrium maintained in a sediment cell?
Through continuous sediment generation, transport, and deposition that balance each other out over time.
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15. What remains constant in the transfer zone under dynamic equilibrium?
The size and shape of the landforms tend to remain constant despite the constant sediment movement.
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16. How can sediment circulation operate within a sediment cell?
Sediment may be eroded from depositional sinks and re-transported back to the source region via offshore currents and wind, completing a cycle.
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17. What factors can interrupt the dynamic equilibrium of a sediment cell?
Variations in energy input, such as storm events, changes in sediment supply, or alterations in coastal morphology (e.g., erosion of cliffs).
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18. How might climate change affect the sediment cell equilibrium?
More frequent storms or changes in sediment supply can alter erosion rates and disrupt the balance between inputs and deposition.
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19. What impact can coastal management in the source region have on a sediment cell?
It can reduce sediment supply (e.g., by constructing sea walls to prevent cliff erosion), altering the cell's sediment budget.
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20. How might coastal management in the transfer region affect sediment supply?
Structures like groynes can trap sediment, preventing its natural movement to sink areas and changing deposition patterns.
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21. What is an example of negative feedback in a sediment cell?
Erosion causing blockfall mass movement; the resulting debris can protect the cliff base, slowing further erosion.
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22. What is an example of positive feedback in a sediment cell?
Wind erosion removing vegetation on a dune, which then increases subsequent erosion and further depletion of dune sand.
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23. What type of coastline typically serves as a source region?
An actively eroding coastline, such as a cliffed coast undergoing continuous erosion.
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24. What is an example of a sink region in a sediment cell?
An outbuilding coastline where deposition occurs, such as beaches or spits.
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25. What is a sediment budget?
It is a measure of the volume of sediment generated, transferred, and deposited within a sediment cell.
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26. Over what temporal scales can dynamic equilibrium be considered?
It can be considered over storm events, seasonal cycles, annual periods, and multi-decadal periods influenced by climate change.
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27. How does a storm event affect the sediment cell dynamic equilibrium?
Storms can temporarily increase erosion and sediment transfer, interrupting the balance until negative feedback restores equilibrium.
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28. What role do groynes play in the context of sediment cells?
Groynes trap sediment by disrupting longshore drift, which can encourage beach outbuilding or alter sediment distribution.
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29. How do sea walls affect sediment supply in a sediment cell?
Sea walls can reduce sediment input by preventing cliff erosion, which might lead to decreased sediment available for transport.
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30. What factors influence the sediment transfer processes in a cell?
The strength and direction of waves, tidal currents, swash/backwash dynamics, and wind direction and speed.
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31. What does the term "closed system" imply for a sediment cell?
It means that the cell's sediment is mostly recycled within its boundaries, with negligible external inputs or losses.
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32. Why is dynamic equilibrium important for understanding coastal systems?
It explains how coastal landforms can appear stable over time despite continuous sediment movement, due to balanced inputs and outputs.
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33. How do negative feedback processes help maintain equilibrium in sediment cells?
They counteract changes—such as by reducing further erosion after significant sediment deposition—thereby stabilizing the system.
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34. How do positive feedback processes affect sediment cells?
They amplify initial changes, leading to accelerated erosion or deposition if not counterbalanced by negative feedback.
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35. What could be a consequence if sediment supply is significantly reduced in a source region?
It may lead to reduced sediment transport and deposition, potentially causing coastal erosion in sink areas due to a lack of replenishment.
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36. How might excessive deposition in a sink region provide negative feedback?
It can form features like offshore bars that reduce wave energy, allowing depositional areas (e.g., dunes) time to recover.
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37. What is the impact of human intervention on the sediment cell system?
Management actions such as building sea walls or groynes can alter sediment supply and movement, potentially disrupting the natural balance.
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38. How does the sediment cell concept aid coastal management planning?
It provides a framework to predict how changes in one part of the system (source, transfer, or sink) can affect the entire coastline.
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39. In what way are sediment cells an example of a dynamic system?
They constantly circulate sediment through interconnected processes and are influenced by varying energy inputs and feedback mechanisms.
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40. How does the sediment cell model integrate sources, transfers, and sinks?
It shows the complete cycle of sediment movement along a coast, from generation at sources, movement via transfers, to deposition at sinks, and sometimes re-erosion.
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41. Why is it important to measure the sediment budget in a sediment cell?
It helps quantify the volume of sediment being generated, transferred, and deposited, which is critical for understanding and managing coastal change.
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42. How can natural or anthropogenic climate change influence a sediment cell's dynamic equilibrium?
Changes such as increased storm frequency or alterations in sediment supply can disrupt the balance, triggering shifts in coastal morphology that may eventually return to a new equilibrium through negative feedback.
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1. What is weathering?
Weathering is the breakdown of rock in situ (at or near the Earth’s surface) without the movement of rock material.
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2. How does weathering relate to mass movement?
Both weathering and mass movement are subaerial processes that weaken rocks and contribute to sediment production and coastal recession.
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3. In which parts of the littoral zone does weathering primarily occur?
Weathering attacks the backshore and foreshore parts of the littoral zone, particularly in the source region of the sediment cell.
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4. What role does weathering play in sediment production?
It creates rock fragments (clasts) that form sediment, thereby influencing rates of coastal recession.
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5. What are the three main types of weathering?
Mechanical (physical), chemical, and biological weathering.
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6. What characterises mechanical weathering?
It involves the physical fragmentation of rock into smaller pieces without any chemical alteration.
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7. What is freeze-thaw weathering?
A type of mechanical weathering where water seeps into cracks, freezes and expands (by about 9%), widening cracks and eventually breaking rock apart.
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8. How does freeze-thaw weathering produce sediment?
Repeated freezing and thawing forces open cracks until large, angular fragments (pebbles, cobbles, boulders) are loosened from the rock.
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9. Why are porous rocks particularly vulnerable to freeze-thaw weathering?
Water in the pores can freeze, prising off individual rock grains and producing sand-sized fragments.
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10. Under what conditions is freeze-thaw weathering most effective?
In environments with abundant water and temperatures that fluctuate around the freezing point; however, it is relatively uncommon on UK coasts.
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11. What is salt crystal growth in the context of weathering?
It is a mechanical weathering process where salt, precipitated from seawater in rock cracks and pores, grows and exerts pressure to break the rock apart.
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12. Why is salt crystal growth particularly common at coasts?
Because the sea is salty and tidal cycles promote the evaporation and precipitation of salt crystals in porous, fractured rocks.
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13. How does the force from salt crystal growth compare to freeze-thaw weathering?
The tensional force from salt crystal growth is less than that produced by freeze-thaw weathering.
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14. What is the process of wetting and drying in weathering?
It involves the expansion of clay minerals when soaked at high tide and their contraction when dried at low tide, eventually leading to rock fragmentation.
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15. Which types of rocks are most affected by wetting and drying?
Rocks containing clay minerals, such as clays and shales.
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16. How does repeated wetting and drying cause rock to crumble?
The cycles of expansion and contraction create stress that eventually causes the rock to fragment and disintegrate.
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17. What is chemical weathering?
Chemical weathering involves chemical reactions that alter and break down rock minerals, forming new compounds and releasing sediment.
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18. What is carbonation in chemical weathering?
Carbonation is a process where rainwater, mixed with carbon dioxide to form weak carbonic acid (pH ~5.6), reacts with calcium carbonate in limestones to form soluble calcium bicarbonate.
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19. What happens to limestone during carbonation?
The rock effectively “disappears” as its calcite dissolves, leaving behind clay particles that were present as impurities.
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20. How does carbonation lead to sediment production?
Cemented clasts in the rock are released as the calcite binder dissolves, forming sediment.
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21. What is hydrolysis in the context of chemical weathering?
Hydrolysis is the breakdown of minerals (especially silicates) by water and dissolved CO₂, transforming feldspar into clay minerals and releasing soluble materials.
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22. Which rock types are most vulnerable to hydrolysis?
Igneous and metamorphic rocks containing feldspar and other silicate minerals, such as granite.
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23. How does hydrolysis produce sand sediment?
The breakdown of feldspar bonds in granite releases quartz grains, which become sand-sized sediment.
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24. What is oxidation in chemical weathering?
Oxidation involves the addition of oxygen to minerals, especially iron compounds, leading to the formation of iron oxides that expand and weaken the rock structure.
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25. How does oxidation affect rock cement?
The oxidation of iron compounds (e.g., haematite) breaks the cement bonds, causing rock fragments to be released as sediment.
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26. Which rocks are particularly susceptible to oxidation?
Sandstones, siltstones, and shales that contain iron compounds.
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27. Why is oxidation more effective in seawater than in pure water?
Seawater contains impurities and a higher ionic content, which accelerate oxidation reactions.
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28. What is biological weathering?
Biological weathering is the breakdown of rock by living or once-living organisms, which can enhance mechanical or chemical weathering processes.
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29. How do tree roots contribute to biological weathering?
Tree roots penetrate rock cracks, and as they grow and expand, they exert tensional forces that widen the cracks, eventually causing rock fragments to break off.
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30. In which zone is tree root weathering most common?
It occurs predominantly on vegetated cliff tops in the backshore zone, away from the direct impact of wave spray.
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31. What is rock boring in biological weathering?
Rock boring is performed by organisms such as piddocks, which drill depressions into soft rock using their sharp, rotating shells and sometimes secrete chemicals that dissolve rock.
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32. Where do piddocks typically live?
They inhabit the foreshore or intertidal zone, where they bore into soft rocks like clays, shales, or carbonate rocks.
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33. What is seaweed acid in biological weathering?
Some seaweeds (e.g., kelp) contain pockets of sulphuric acid that, when released, chemically attack rock minerals like calcium carbonate, similar to the process of carbonation.
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34. How does weathering influence coastal recession?
Weathering weakens rocks, making them more vulnerable to mass movement and marine erosion, which accelerates cliff retreat.
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35. What is the relationship between weathering in the foreshore zone and marine erosion?
Rocks weathered in the foreshore zone are more rapidly eroded by marine processes (like hydraulic action) because they have been weakened and are easier to fragment.
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36. How can weathering affect the development of wave-cut notches?
Weathered rock in the notch zone can deepen the notch more rapidly, leading to increased undercutting and eventual mass movement collapse.
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37. How slow are weathering rates, even in hot, wet climates?
For example, basalt (an igneous rock) weathers at a rate of only about 1–2 mm per 1,000 years.
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38. Which climatic conditions encourage chemical and biological weathering?
Hot, wet climates promote these processes by enhancing the reactions of water and biological activity.
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39. How does temperature affect carbonation?
Carbonation increases in winter because calcium bicarbonate is more soluble in cold conditions, enhancing the chemical reaction.
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40. How do the different weathering processes interact to influence sediment production?
Mechanical, chemical, and biological weathering often work together to break down rock, producing a range of sediment sizes that contribute to coastal erosion and deposition.
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41. Why is understanding weathering important for coastal management?
It helps predict rates of cliff recession and sediment supply, crucial for managing coastal erosion and planning mitigation measures.
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42. What is the overall impact of weathering on the coastal environment?
Weathering not only produces sediment but also weakens the coastal structure, making it more susceptible to erosion, mass movement, and long-term landscape change.
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1. What is mass movement?
The downslope movement of rock and soil under the force of gravity.
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2. What drives mass movement?
Gravity; it occurs when the downslope gravitational force exceeds friction and internal cohesion.
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3. How does mass movement relate to coastal erosion?
It contributes to cliff recession by detaching and moving rock and sediment from the coastline.
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4. What types of mass movement are common on coasts?
Blockfall (or rockfall), rotational slumping, and landslides.
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5. What is blockfall?
The rapid detachment of rock fragments (or blocks) from a steep cliff, which then fall or bounce downslope.
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6. At what slope angle is blockfall most likely to occur?
On slopes steeper than about 40°.
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7. What processes initiate blockfall?
Mechanical weathering processes like freeze-thaw and salt crystal growth, as well as marine erosion (hydraulic action, abrasion, and undercutting).
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8. How does freeze-thaw weathering contribute to blockfall?
Water enters cracks, freezes (expanding by ~9%), and exerts tension that widens cracks until fragments detach.
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9. What role does salt crystal growth play in blockfall?
Seawater penetrates rock cracks; as water evaporates, salt precipitates and grows, exerting pressure that breaks rock fragments away.
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10. How does marine erosion lead to blockfall?
Waves undercut the cliff (forming a wave-cut notch) and remove supporting material, reducing the resistive force.
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11. What geological features predispose cliffs to blockfall?
A high density of joints, faults, or bedding planes, and a steep or near-vertical dip of strata.
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12. How rapid is a blockfall event?
Blockfall can occur very rapidly—in just a few seconds.
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13. Can blockfall involve entire sections of a cliff?
Yes; sometimes a whole section detaches, especially when undercutting has removed significant support.
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14. What is rotational slumping?
A form of mass movement where a block of material moves downslope along a curved failure plane, often as a coherent mass.
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15. How does rotational slumping differ from blockfall?
Slumping involves gradual, intact movement along a curved plane, while blockfall is sudden, discrete detachment of fragments.
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16. In which lithologies is rotational slumping common?
In weak or unconsolidated materials such as boulder clay, sands, gravels, clays, and shales, and in rocks with complex geology.
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17. How does water facilitate rotational slumping?
Water increases the weight (gravitational force) and lubricates the failure plane, reducing friction and aiding movement.
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18. What coastal feature can accelerate rotational slumping?
The formation of a wave-cut notch by marine erosion undercuts the base of the cliff, removing support.
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19. Can you provide an example of rotational slumping?
At Christchurch Bay near Barton-on-Sea, unconsolidated sands overlie clay with a seawards-dipping bedding plane, leading to slumping.
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20. What is a landslide in coastal settings?
The downslope movement of discrete rock blocks along a relatively flat or linear slip plane while maintaining contact with the cliff.
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21. How do landslides differ from slumping?
Landslides involve sliding of individual, well-defined blocks along a flat slip plane, whereas slumping is a continuous, curved mass movement.
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22. Which rocks are prone to landslides?
Consolidated rocks with well-developed joints or bedding planes, such as Carboniferous limestone or granite.
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23. What initiates a landslide?
Mechanical weathering weakening the rock, marine erosion undercutting the cliff base, and factors like heavy rainfall that lubricate the slip plane.
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24. How does rainfall affect landslides?
Rainfall increases pore water pressure, lubricates the slip plane, and reduces friction, thereby triggering sliding.
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25. What is the typical slip plane in a landslide?
A relatively flat, linear surface created by joints or bedding planes that dip seaward.
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26. How does the lithology influence the type of mass movement?
Unconsolidated material (e.g., boulder clay) tends to slump, while consolidated rock (e.g., limestone, granite) is more likely to slide.
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27. What is the role of water in all mass movement processes?
Water adds weight, increases gravitational force, and reduces friction through lubrication, promoting downslope movement.
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28. What are flows in the context of mass movement?
Flows occur when fine-grained sediment (silt and clay) mixes with water, loses cohesion, and flows downslope.
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29. What is the difference between mudflows and earthflows?
Mudflows are less viscous and contain finer sediment, while earthflows are more viscous and contain larger, more cohesive sediment.
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30. What are solifluction flows?
They are earthflows in cold environments, occurring in the unfrozen layer between permafrost and vegetation turf (tundra).
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31. How can the speed of mass movement vary?
It ranges from extremely rapid (blockfall in seconds) to slow (rotational slumping over minutes, days, or even years).
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32. How does mass movement contribute to coastal recession?
By detaching and transporting rock and soil, mass movement undercuts cliffs, leading to accelerated erosion and cliff retreat.
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33. What is the effect of an earthquake on coastal mass movement?
Earthquakes can trigger sudden mass movements, such as blockfalls or landslides, by rapidly reducing the resisting forces.
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34. How does the orientation of bedding planes affect mass movement?
Seaward-dipping bedding planes reduce resistance to gravity, making sliding or slumping more likely.
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35. What factors can increase the risk of mass movement on a coastal cliff?
Weak or complex geology, steep slopes, intense weathering, high pore water pressure, and undercutting by marine erosion.
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36. How can repeated tidal action influence mass movement?
Tidal cycles can erode and undercut the cliff base, removing support and promoting blockfall or slumping.
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37. What is meant by “undercutting” in the context of mass movement?
The removal of support at the base of a cliff by marine erosion, which destabilizes the rock
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1. What are the main coastal landforms produced by mass movement?
They include rotational scars, talus scree slopes, and terraced cliff profiles.
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2. How is a talus scree slope formed?
It forms from the accumulation of angular blockfall debris at the cliff foot, often as a fan-shaped mound.
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3. What is blockfall (or rockfall)?
Blockfall is the rapid detachment of rock fragments from a cliff, which then fall or bounce downslope.
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4. What role does undercutting by wave-cut notches play in mass movement?
Undercutting removes supporting material from the cliff base, triggering larger blockfalls and leading to extensive talus scree slopes.
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5. What are the typical slope angles of a talus scree slope?
They usually have slope angles between 34° and 40°, with larger fragments maintaining a steeper angle of repose.
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6. Provide an example of a significant blockfall event and its impact.
In April 2013 at St Oswald's Bay, an 80 m section of chalk cliff detached, forming a large fan-shaped talus scree slope extending 30 m into the sea, which now protects the cliff for a decade or more.
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7. How do talus scree slopes protect the cliff?
They absorb wave energy and act as a physical barrier, reducing further erosion at the cliff base.
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8. What is rotational slumping?
Rotational slumping is the downslope movement of a block of rock along a curved failure plane, usually occurring as a coherent mass.
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9. What is a rotational scar?
A rotational scar is a fresh, curved, unweathered, and unvegetated rock surface exposed on the cliff face as a result of rotational slumping.
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10. How does rotational slumping contribute to terraced cliff profiles?
The detached section from rotational slumping can form a distinct step or terrace on the cliff, often with a beach forming at the base.
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11. What does a terraced cliff profile indicate?
It indicates successive mass movement events, where rotational slumping has repeatedly detached sections of the cliff, leaving stepped surfaces.
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12. How does vegetation interact with these mass movement landforms?
Vegetation often remains on the upper parts of a slump, accentuating the terraced appearance of the cliff and stabilizing the upper sections.
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13. Why are talus scree slopes important for coastal sediment budgets?
They provide a source of sediment that can be redistributed by marine processes and help protect the cliff from further erosion.
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14. What factors control the slope angle of a talus scree slope?
The size and angularity of the debris control the angle of repose; larger, more angular fragments typically form steeper slopes.
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15. How does a rotational scar differ from a blockfall deposit?
A rotational scar is a smooth, curved cliff face resulting from coherent slumping, while blockfall deposits are loose, fan-shaped accumulations of detached rock.
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16. How can a large blockfall event influence coastal management?
It can significantly alter the coastline, and the resulting talus scree slope may provide temporary protection against further erosion, affecting management strategies.
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17. How can terraced cliff profiles be used to infer past mass movement events?
Their stepped structure records sequential slumping events, allowing reconstruction of past erosion processes and rates.
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18. What triggers mass movement in coastal environments?
Triggers include mechanical, chemical, and biological weathering, undercutting by wave erosion, and increased pore water pressure.
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19. How does the angularity of rock fragments affect their deposition?
Angular fragments tend to interlock and form more stable slopes compared to rounded debris, which can be more easily transported.
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20. What is the overall significance of mass movement in shaping coastal landforms?
Mass movement is a key process that not only produces distinctive landforms but also supplies sediment to the coastal system, influencing erosion, deposition, and overall landscape evolution.
