Geography π | Coasts π | Flashcards
1
Q
What is the swash?
A
Water that rushes up the beach when the wave breaks.
2
Q
What is the backwash?
A
Water that runs back down the beach, back out to the sea under the force of gravity.
3
Q
What factors affect the size of a wave?
A
- Strength of wind
- Distance the wave has travelled
- How long the wind has blown for
4
Q
What is the fetch?
A
The distance the wave has travelled
5
Q
How is a wave formed?
A
- Wind blows across the sea surface
- Friction produces a swell
- Wind energy makes particles rotate in the swell, moving the wave forward.
6
Q
Why do waves break?
A
- The bottom of the wave touches the bed, slowing.
- The wave top continues faster, the wave leaning forward
- The top of the wave topples
7
Q
Which wave builds up the beach?
A
Constructive wave
8
Q
Which wave takes sediment away from the beach?
A
Destructive wave
9
Q
Which wave type is higher energy?
A
Destructive wave
10
Q
Which wave type is steeper?
A
Destructive wave
11
Q
Which wave type has a strong swash?
A
Constructive wave
12
Q
What is abrasion in the sea?
A
When sand and shingle is hauled at the cliff face with a scraping effect.
13
Q
What is attrition in the sea?
A
When material in the sea collides with other material, breaking to smaller pieces.
14
Q
What is solution (erosion) in the sea?
A
When chemicals in the water erode the coastline and sea material.
15
Q
For a bay to form, there needs to be __
A
Bands of less resistant rock alongside bands of more resistant rock, perpendicular to the sea.
16
Q
What is the main form of erosion at bays?
A
Hydraulic action and abrasion
17
Q
What is the headland?
A
Hard rock that sticks out from the sides of bays, sheltering it.
18
Q
Order of the erosion of a headland.
A
Crack-cave-arch-stack-stump
19
Q
How is a cave formed?
A
- A crack in the cliff is widened by hydraulic action, the headland weakening
- Abrasion and hydraulic action widens the crack and creates a cave.
20
Q
How is an arch formed?
A
- With more erosion, an arch forms as the bay breaks through the headland
21
Q
How is a stack formed?
A
The rock of an arch weakens, the roof falling and creating a stack.
22
Q
How is a stump formed?
A
The stack erodes more, leaving behind a stump
23
Q
When is a stump visible?
A
Only at low tide.
24
Q
What is a wave-cut platform?
A
The narrow, flat rocky platform at the base of a cliff, smooth from abrasion.
25
How is a wave-cut notch formed?
Erosion wears the bottom of a cliff through hydraulic action.
26
How does a wave-cut platform expand?
The notch deepens and undercuts the cliff, eventually collapsing due to gravity. The cliff retreats.
27
What is longshore drift?
The movement of sediment along the coastline, helped by prevailing wind.
28
How does longshore drift move sediment?
The prevailing winds sweep sediment to the beach, the backwash bringing it back to the sea at right angles to the beach.
29
What is a spit?
A long narrow finger of land sticking out into the sea from the land. They form on coasts with longshore drift.
30
How is a spit formed?
1. If the coastland bends sharply, sediment extends the headland from longshore drift.
2. It builds up to form a finger of land.
31
How does the end of the spit curve?
Waves and tidal currents can cause the end of the spit to make a hook.
32
Why may a spit, found in between two headlands and a river mouth, not join the two headlands?
The flow of a river prevents it from joining the other headland.
33
What is found behind a spit?
Sheltered water behind the spit deposits mud and salt marshes are formed.
34
What is a spit known as if it joins the opposing headland?
A sand bar.
35
What is formed behind a sand bar?
A lagoon.
36
What is a beach?
A deposit of sand and shingle at coasts, sandy beaches found mostly in sheltered bays.
37
How does an embryo dune form?
A deposited obstacle has sand formed around it, creating an embryo dune.
38
How is a fore dune formed?
The embryo dune is developed and builds up in size.
39
How is a dune stabilized?
Vegetation, such as marram grass, stabilizes the dunes because of their long root hairs finding water.
40
Where is more vegetation found in sand dunes?
At the back, further from the sea.
41
How does salinity affect vegetation in dunes?
The lower salinity and rotting vegetation at the back increases fertility and vegetation.
42
What is a dune slack?
Depressions in the sand formed by wind, sometimes with ponds inside them.
43
Where are coral reefs found geographically?
In between the tropics of cancer and capricorn.
44
What conditions are needed for coral reefs to exist?
- Warm water temperature
- High salinity
- Clear water
- Enough light
45
What is a coral reef?
An underwater ecosystem full of polyps - which build calcium carbonate skeletons.
46
What temperature do coral reefs grow best at?
Between 18-28 degrees celcius.
47
Below what temperature can coral not grow?
Below 16 degrees celcius.
48
Why are coral reefs found between the tropics?
There is little variation in sea temperature between the tropics due to currents.
49
How does coral react to freshwater?
The coral dies, so when rivers flow into reefs they die.
50
How does coral react to silty water?
It blankets the coral and restricts currents, which kills the corals.
51
What depth do corals need to be at?
At 37m.
52
What are the types of coral reefs?
Fringing reef, barrier reef, atoll.
53
What is a fringing reef?
A coral platform that grows out to the sea attached to the mainland. A narrow, shallow lagoon lies on top.
54
What is a barrier reef?
A reef formed at a shallower area away from the mainland, water between too deep for coral to grow. A large lagoon forms
55
What is an atoll?
A reef that develops around islands, circles attached to the mainland. A rise in sea level makes them grow upwards to light. A circular lagoon forms.
56
What is a mangrove swamp?
A vegetated area found along sheltered tropical coastlines and estuaries. The mangroves can withstand salt.
57
What is a halophytes?
Something that needs to live in salty water.
58
What temperature do mangrove swamps need to be at?
Remain over 20 degrees celcius, with little variation.
59
What conditions do mangrove swamps need?
- Calm waters
- Hot temperature
- Salty water
60
What seasonal temperature range are mangrove swamps restricted to?
5 degrees celcius,
61
How do mangroves protect coastlines?
They act as a natural barrier and flood defence.
62
How do mangrove swamps protect coral reefs?
They filter pollutants and sediment from reaching coral reefs.
63
Geographically, where are mangrove swamps found?
Between the tropics (32N-38S), lining coasts.
64
Why are mangrove swamps being cleared?
- They take up thousands of acres of land, usable for agriculture
- The shrimp agriculture industry clears them for shrimp ponds.
- Tourists pollute
- Urbanization
- High quality charcoal is found.
65
How are mangrove swamps turned into shrimp ponds?
Channels are dug into the swamp to supply freshwater and seawater, disrupting salinity.
66
How can we protect mangroves?
- Afforestation
- Limiting urbanization
- Creating govt. regulations.
67
For what reasons do we protect coasts?
- There are often high-income settlements along coastlines (TLDR, money.)
- They are economically valuable for tourism (TLDR, money.)
- Some coastal land is very valuable (TLDR, money.)
- Protecting ecosystems (Which we rarely do, because no money)
68
What coastal land are we more likely to protect?
Economically valuable land; we are less likely to protect land with few residents or low income farmland.
69
What are the coastal hard engineering strategies?
- Groynes
- Sea walls
- Rock armor
- Gabions
- Revetments
- Offshore breakwaters
70
What are groynes?
Wooden barriers at right angles to the beach to trap sediment and prevent it from being moved by longshore drift.
71
What are the advantages of groynes?
- Builds up beach, encouraging tourism
- Traps sediment being carried by longshore drift
72
What are the disadvantages of groynes?
- Starves beaches further down coastline, increasing erosion there.
- Unattractive
73
What are sea walls?
Concrete walls placed at the base of a cliff to prevent erosion, curved to reflect energy back into the sea.
74
What are the advantages of sea walls?
- Effective at protecting the base of a cliff
- Can create promenades for walking
- Most effective
75
What are the disadvantages of a sea wall?
- Powerful waves will erode it over times
- They are expensive
- A sea wall could actually increase erosion as the reflection of energy creates a strong backwash, erosion taking place under the wall.
76
What is the cost of a sea wall?
Β£2000 per meter.
77
What is rock armor?
Large boulders placed at the base of a cliff to absorb wave energy.
78
What are the advantages of rock armor?
- Cheap and easy to maintain
- Can be used for fishing
- Less manmade looking than other strategies
79
What are the disadvantages of rock armor?
- Very difficult and expensive to transport
- Looks different to local geology as rocks are imported.
80
What are gabions?
Metal cages that enclose rocks and boulders to absorb wave energy.
81
What are the advantages of gabions?
- Cheap
- Absorbs wave energy
82
How expensive are gabions?
Β£100 per meter.
83
What are the disadvantages of gabions?
- Short lifespan
- Unattractive and unnatural cages
84
What are revetments?
Wood or concrete-slated barriers at the top of beaches to protect the base of cliffs.
85
What are the advantages of revetments?
- Cheaper than other methods
- Less visual impact
86
What are the disadvantages of revetments?
- Ineffective for higher energy waves.
87
What are offshore breakwaters?
Large concrete blocks and boulders offshore, reducing wave power or changing direction.
88
What are the advantages of offshore breakwaters?
Retains appearance of beaches and cliffs
89
What are the disadvantages of offshore breakwaters
- Unattractive in the sea
- Not very effective for high energy waves.
90
What are the coastal soft engineering strategies?
- Beach nourishment
- Dune nourishment
- Managed retreat
91
What is beach nourishment?
Replacing beach material carried away by pumping sand often offshore, onto the beach.
92
What are the advantages of beach nourishment?
- Blends in with the beach
- Can increase the size of the beach which appeals to tourists
93
What are the disadvantages of beach nourishment?
- Constant replacing of sand
- Sand has to be brought in from elsewhere
- Dredging affects natural environment
- Costly
94
What is dune nourishment?
Placing marram grass on sand dunes for stabilisation
95
What are the advantages of dune nourishment?
- Cheap
- Natural-looking coastline
96
What are the disadvantages of dune nourishment?
- Damaged by storm waves
- Areas must be zoned off to the public
97
What is dune fencing?
Fences placed around a dune to reduce wind speed and encourage foredune deposition.
98
What is managed retreat?
Areas of low-lying coasts are allowed to flood and erode, that sediment being deposited into the beach. Mostly in low-value areas.
99
What are the advantages of managed retreat?
- Costless
- Creates salt marshes and provides wildlife habitats
100
What are the disadvantages of managed retreat?
- Land reclaimed by the sea is lost
- Landowners must be compensated Β£5-10k per hectare
