Coastal Systems and Landscapes: Systems and processes Flashcards
Sources of energy in coastal environments: winds, waves (constructive and destructive), currents and tides. Low energy and high energy coasts. Sediment sources, cells and budgets. Geomorphological processes: weathering, mass movement, erosion, transportation and deposition. Distinctively coastal processes: marin (62 cards)
1
Q
Define fetch:
A
The distance the wind blows
2
Q
What is a sediment cell?
A
The largely self-contained stretch of a coastline.
3
Q
Define backshore:
A
The part of the beach lying between the beach face and the coastline.
4
Q
Define foreshore:
A
The area between the high tide mark and low tide mark.
5
Q
What is wave height?
A
The difference between the elevations of a crest and a neighbouring trough.
6
Q
How does chemical weathering occur in a coastline?
A
- Carbonation
- Oxidation
- Solution
7
Q
How does biological weathering occur in a coastline?
A
- Plant roots
- Birds
- Decaying vegetation
8
Q
How does mechanical weathering occur in a coastline?
A
- Freeze-thaw
- Salt crystallisation
- Wetting and drying
9
Q
What is a sediment budget?
A
A coastal management tool used to assess the gains and losses of sediment within a sediment cell.
10
Q
What is a longshore current?
A
Current that flows parallel to the shore within the zone of breaking waves.
11
Q
Outline low energy coastlines:
A
- A coastline where wave energy is low.
- Have less powerful waves and occur in sheltered areas where constructive waves prevail, causing sandy areas.
- There are landforms of deposition present as the rate of deposition is greater than the rate of erosion.
12
Q
Outline high energy coastlines:
A
- Coastline where strong, steady prevailing winds create high energy , powerful (usually destructive) waves.
- Typically have rocky headlands and landforms, as well as destructive waves.
- Typically eroding as the rate of erosion is greater than the rate of deposition
13
Q
What is upwelling?
A
Movement of cold water from deep in the ocean towards the surface
14
Q
Why do constructive waves have a weak backwash?
A
Water rapidly looses volume and energy as it comes up through the beach material, so it has an insufficient force to pull sediment out.
15
Q
Give the 6 sediment sources:
A
- Rivers
- Cliff erosion
- Wind
- Glaciers
- Offshore
- Longshore drift
16
Q
What are berms?
A
Ridges in the beach.
17
Q
How are rivers a sediment source?
A
- Most sediment in coastal zones is from rivers- especially in high rainfall areas with significant cliff erosion
18
Q
How is cliff erosion a sediment source?
A
- In unconsolidated areas cliffs are eroded easily.
- In some areas coasts can erode up to 10m annually - providing a significant sediment input.
19
Q
How is wind a sediment source?
A
- The wind is a coastal energy source and can cause sand to be blown along or up a beach.
- Sediment transport by wind may occur where there are sand dunes or in glacial desert environments which provide sediment inputs.
20
Q
How are are glaciers sediment source?
A
- In some coastal environments (e.g. Alaska, Antartica) glaciers flow directly into the ocean depositing sediment that was stored in the ice.
- This occurs when glaciers calve (when ice breaks off the glacier)
21
Q
How is offshore a sediment source?
A
- Sediment is transferred to the coastal zone when waves, tides and currents erode offshore sediment sinks e.g. offshore bars.
- Storm surges or tsunami waves may also transfer sediment into the coastal zone.
22
Q
How is longshore drift a sediment source?
A
- Sediment is moved along the beach due to prevailing winds which alter the direction of the waves.
- This allows for sediment to be transported from one section of a coastline (output) to another stretch of a coastline (input).
- Swash approaches the coast at an angle due to prevailing winds, transferring sediment along the beach.
- The backwash pulls the sediment directly back down the beach.
- The swash then transfers the sediment along the coastline and the process repeats.
23
Q
What is the littoral zone?
A
- The area of land between a cliff or dune on the coast and the offshore area that is beyond the influence of the waves.
- It is impacted by short-term factors e.g. tides, storm surges.
- It is impacted by long-term factors e.g. changes in sea level, human intervention.
24
Q
Define offshore:
A
The area beyond the influence of waves
25
Define onshore:
The area of land that is not covered by the sea, but is very close to it.
26
How are waves formed?
- Winds move across the surface of the water, causing frictional drag (resistance to the wind by the water) which creates small ripples and waves.
- This leads to a circular orbital motion of the water particles in the ocean.
- As the seabed becomes shallower towards the coastline, the orbit of the wave particles becomes more elliptical, leading to more horizontal movement of the waves.
- The wave height increases, but the wavelength and wave velocity both decrease.
- This causes water to back up from behind the waves until the wave breaks and surges up the beach.
27
How does strength of the wind impact wave energy?
- The larger the difference in pressure between two areas the stronger the wind.
- As waves are caused by the wind, stronger wind also means stronger waves.
28
How does duration of a wind impact wave energy?
If the wind is active for longer periods of time, then the energy of the waves will build up and increase.
29
How does size of the fetch impact wave energy?
- The distance over which the wind blows and the larger it is, and the more powerful the waves will be.
30
Outline features of constructive waves:
- Formed by weather systems that operate in the open ocean.
- Long wavelength
- 6-9 per minute
- Low waves, which surge up the beach
- Strong swash, weak backwash
- Occurs on gently sloped beach
31
Outline features of destructive waves:
- Localised storm events with stronger winds operating closer to the coast.
- Short wavelength
- 11-16 per minute
- High waves, which plunge on the beach
- Weak swash, strong backwash
- Occurs on steeply sloped beaches.
32
Give an example of a negative feedback loop in beaches and waves:
- The presence of constructive waves causes deposition on the beach, which in turn leads to the beach becoming steeper.
- Steeper beaches favour the formation of destructive waves which are then likely to occur.
- The destructive waves erode the beach, reducing the beach profile and leading to the formation of constructive waves.j
33
Outline tides and their causes:
- Tides occur due to the gravitational pull of the sun and moon changing water levels of the sea- they cause high and low tides.
- Tidal range: The difference in height between the tides.
- The highest high and lowest low tides: When the sun and moon are in alignment. Both of their gravitational forces combine to effectively pull the oceans towards them to cause the highest tides, and lowest tides on the opposite side of the globe.
- The lowest high and highest low tides: When the sun and moon are perpendicular to eachother. Both their gravitational forces act against eachother, so the overpull is minimised at high tide creating a lower tide (neap tide)
34
Outline rip currents:
- Powerful underwater currents occurring close to the shoreline when plunging waves cause a buildup of water at the top of the beach.
- The backwash from waves is forced under the surface (due to resistance from breaking waves) forming an underwater current.
- This flows away from the shore more quickly due to beach feature (e.g. gap in sandbar) creating a riptide.
35
Outline wave refraction:
- The process by which waves turn and lose energy around a headland on uneven coastlines.
- The wave energy is focused on the headlands , creating erosive features in these areas.
- The energy is dissipated in bays leading to the formation of features associated with lower energy coastlines e.g. beaches
36
Give an example of a negative feedback loop for wave refraction:
- Due to different rock strengths, erosion leads to the formation of headlands where resistant rock exists and softer rock erodes.
- This then increases the forces of erosion on the headlands and reduces erosion on the bays (as wave refraction dissipates wave energy and a beach protects the coastline behind)/
- Eventually the headland is eroded away, which increases erosion within the bays.
37
What is corrosion?
Sand and pebbles are picked up by the sea from an offshore sediment sink (or store) and hurled against the cliffs at high tide, causing the cliffs to be eroded
38
What is abrasion?
Process where sediment is moved along the shoreline , causing it to be
worn down over time .
39
What is attrition?
Wave action cause rocks and pebbles to hit against each other , wearing each other down and so becoming round and eventually smaller (doesnt affect the coastline itself- it is just an erosive process in the coastal environment).
40
What is hydraulic action?
- As a wave crashes onto a rock or cliff face, air is forced into cracks, joints and faults within the rock.
- The high pressure causes the cracks to force apart and widen when
the wave retreats and the air expands.
- Over time this causes the rock to fracture
41
What is wave quarrying?
- When breaking waves that hit the cliff face exert a pressure up to 30
tonnes per m ².
- The force of the breaking wave hammers the rocks surface , shaking and weakening it and leaving it open to erosion from hydraulic action and abrasion.
42
What is the 'traction' transportation of sediment?
Large, heavy sediment rolls along the sea bed pushed by currents.
43
What is the 'saltation' transportation of sediment?
- Smaller sediment bounces along the sea bed, being pushed by currents .
- The sediment is too heavy to be picked up by the flow of the water
44
What is the 'suspension' transportation of sediment?
Small sediment is carried within the flow of the water.
45
What is the 'solution' transport of sediment?
Dissolved material is carried within the water.
46
Outline longshore drift:
- Waves hit the beach at an angle determined by the direction of the prevailing wind
- The waves push sediment in this direction and up the beach in the swash
- Due to gravity, the wave then carries sediment back down the beach in the backwash
- This moves sediment along the beach over time
- It is one of the reasons why when swimming in the sea, you
often move along the coast in a particular direction.
47
Outline freeze thaw as a type of physical weathering:
- Water collects in crack in a cliff
- Water freezes and expands, widening the crack
- Ice thaws, deepening the crack for more water to enter
- Process is a loop until part of cliff breaks off.
48
Outline salt crystallisation as a type of physical weathering:
- Salt water enters a crack, the water evaporates, leaving salt behind.
- Salt crystals grow over time, exerting pressure on the rock, forcing the cracks to widen.
49
Outline wetting and drying as a type of physical weathering:
- Rocks such as clay expand when wet and contract again when drying.
- Frequent cycles of wetting and drying at the coast can cause these rocks and cliffs to break apart.
50
Outline carbonation as a type of chemical weathering:
- Rainwater absorbs CO2 from the air to create a weak carbonic acid which reacts with the cliff, causing it to become weaker.
51
Outline oxidation as a type of chemical weathering:
- When minerals within a rock become exposed to the air through cracks and fissures
- Causes the minerals to become oxidised and will increase its volume, causing the rock to crumble.
52
Outline solution as a type of chemical weathering:
When rock minerals such as rock salt are dissolved.
53
Outline plant roots as a type of biological weathering:
Roots of plants grow into the cracks of rocks, exerting pressure onto the rock, eventually splitting it.
54
Outline birds as a type of biological weathering:
Some birds, such as Puffins, dig burrows into cliffs, weakening them and making erosion more likely.
55
Outline decaying vegetation as a type of biological weathering:
Water that flows through decaying vegetation and then over coastal areas will be acidic, causing chemical weathering.
56
Name the 6 types of mass movement:
- Soil creep
- Mudflows
- Rockfall
- Landslide
- Slump
- Runoff
57
Outline soil creep as a type of mass movement:
- The slowest but most continuous form of MM (movement of soil particles downhill)
- Particles rise and fall due to wetting and freezing, causing soil to move down the slope.
58
Outline mudflows as a type of mass movement:
- An increase in the water content of soil reduces friction, leading to earth and mud to flow over underlying bedrock , or slippery materials such as clay.
- Water gets trapped within the rock, increasing pore water pressure, forcing water particles apart and weakening the slope.
59
Outline rockfall as a type of mass movement:
- Occurs when sloped cliffs (usually vertical cliff faces) are exposed to mechanical weathering.
- Leads to rock buildup building up at the base of the slope.
60
Outline landslides as a type of mass movement:
- Heavy rainfall leads to water between joints and bedding planes within cliffs parallel to the cliff face, reducing friction and leading to a landslide.
- A block of intact rocks move down the cliff face very quickly
61
Outline landslip as a type of mass movement:
- Occurs on curved slopes, often in weak, unsolicited clay and sand areas.
- A build up in pore water pressure causes the land to collapse under its own weight, leaving a scarred appearance to the cliff face.
62
Outline runoff as a type of mass movement:
- The water in the form of overland flow erodes the cliff face and coastal area, and picks up sediment, that enters the littoral zone (via suspension).
- Also responsible for increasing pollution in coastal areas if it picks up waste or excess chemicals.
