Coasts Flashcards
1
Q
What are coasts shaped by
A
The sea and the action of waves. The processes that take place are erosion, transportation and deposition.
2
Q
What is fetch
A
The distance in which the wind has blown
3
Q
What are waves caused by
A
The transfer of energy from the wind
4
Q
What does a waves energy depend on
A
It’s fetch, the strength of the wind blowing,, the length of time over which the wind has blown.
5
Q
How do waves break
A
A prevailing wind causes waves to start out sea and have a circular orbit, as waves approach the shore friction slows the base of the wave. This causes the orbit to become elliptical until the top of the wave breaks over. Water swashes up the beach and water from previous Wave returns to the sea as back wash.
6
Q
What is a constructive wave
A
Waves Created in calm weather that build up the beaches
7
Q
What is a destructive wave
A
A wave formed in stormy conditions that erodes the beach.
8
Q
Height of a constructive wave
A
Under a metre
9
Q
Height of destructive wave
A
Over a metre
10
Q
Shape of constructive wave
A
Long in proportion to its height
11
Q
Shape of a destructive wave
A
High in proportion to its length
12
Q
What is the swash and backwash like in a constructive wave
A
Swash is strong and backwash is weak
13
Q
What is the swash and backwash like in destructive waves
A
Swash is weak but backwash is strong
14
Q
How many constructive waves could occur per minute
A
Under 11
15
Q
How many destructive waves could occur in a minute
A
Over 13
16
Q
Season in which constructive waves are more common
A
Summer
17
Q
Season in which destructive waves are more common
A
Winter
18
Q
What is a headland
A
A cliff promontory which juts out into the sea such that it is surrounded by water on 3 sides
19
Q
What is a bay
A
A crescent shaped indention in the coastline found between two headlands. It usually has a beach which may be composed of sand or shingle.
20
Q
Formation of headland and bays
A
Waves erode the les resistant rock and the more resistant rock. The less resistant rock erodes due to rapid erosion such as that of abrasion, hydraulic action and some solution.
Once the bay has formed the headlands are left sticking out so sea where their hard rock has been resisted of erosion.
21
Q
Where and when will the rate of erosion be higher?
A
Coastline is exposed to a large fetch.
Strong winds blow for a long time creating destructive waves.
An area with no beach to act as a buffer between sea and cliffs.
Areas of soft rock.
A rock has many joints.
Waves converge on a headland (wave refraction) and gain height and erosive energy.
22
Q
What is wave refraction
A
Their energy is concentrated Around headlands but reduced around bays.
Waves then tend to approach the coastline parallel to it, and their energy decreases as water depth decreases.
23
Q
What is a cliff
A
A steep or vertical face of rock often found at the coast.
24
Q
Formation of cliffs
A
Formed by weathering which weakens the top of the cliff whilst the sea attacks and waves erode the base which creates a wave cut notch. The notch increases in size causing the cliff to collapse, the backwash Carries the rubble towards the sea and it is repeated again.
Wave cut notch-undercut at base
25
What is a wave cut platform
A wide gently sloping surface at the foot of a cliff, left behind when cliff retreats- exposed at low tide.
26
Formation of wave cut platform
The wave cut notch created, size gradually increases. As there is now nothing to support the cliff face above the force of gravity weakens the rock which is then broken off and eroded by attrition in the sea. The cliff retreats and leaves a wave cut platform, from where the cliff used to be. An area of flat rock is left at the base of the new cliff. This process is repeated resulting in wider wave cut platforms.
27
Characteristics of wave cut Platform
Slopes gently down to the sea at a 3-5* angle.
Bare rock, smoothed in places by attrition
Deep cracks in some places
Covered at high tide and exposed at low tide
An oval pitted appearance of bare rock interspersed with rock pools.
28
Formation of caves, arches, stacks and stumps.
A large crack opened up by hydraulic action.
The crack grows into a cave by hydraulic action and abrasion.
The cave becomes larger.
The cave breaks through the headland forming a natural arch.
The arch is eroded and collapses.
This leaves a tall rock stack.
The stack is eroded forming a stump.
29
What is a beach
A landform of coastal deposition that lies between the High and low tide levels.
30
```
Describe the characteristics of a sandy beach
Referring to its ...
Gradient
Dominant wave
Distance stretched inland
Back of beach
```
A sandy beach is generally shallow and flat, it's dominant wave is constructive.
It's distance stretching inland is a long way and at the back of the beach you will find sand dunes (sometimes).
31
Low tide In a sandy beach what is formed
Small water filled depressions called runnels form. These are separated by small sandy ridges running parallel to shore. The wet sand may have a rippled appearance.
32
```
Describe the characteristics of a pebble beach
Referring to its...
Gradient
Dominant wave
Distance inland
Back of beach
```
The gradient on a pebble beach is generally steep, the dominant wave is destructive and the distance inland is not far.
At the back of the beach you can find large pebbles, pebble size increases towards the back of the beach.
33
How do sandy beaches form
In shelters bays, low energy constructive waves transport material onto the shore. The swash is stronger than the backwash,so sediment is slowly but constantly moved up the beach.
Once the tide has gone out, there is more material on the beach than before.
34
How do pebble beaches form
In Exposed beaches where there is large fetch.
Destructive waves plunging nature along with their stronger backwash means that pebbles are not moved far up the beach, which makes the beach profile steep.
A storm beach may form when there is wind, stormy weather and waves hurl boulders and large pebbles at the back of the beach.
35
Why and how do beach profiles change in winter
In winter destructive waves are present as the waves excavates material from the beach creating a concave profile. The beach will become much narrower, steeper and smoother.
36
Why and how do beach profiles change in summer
The beaches experience constructive waves, sand will slowly return to the beach and berms and sand dunes typically recover, as the sediment isn't lost by offshore. The key change is the berm as it changes the most seasonally which affects the shape the most.
37
What is a berm and how is it formed
A step like landform (terrace) on a beach that has formed in the back-shore, above the water level at High tide.
They are formed as sand or shingle slowly ,cover up a beach by successive (one after another) income tides.
Common In shingle beaches.
38
What are runnels/&ripples and how are they formed
They only form on beaches with a shallow gradient. They form as a simple drainage route for tides. Typically found on sandy beaches.
39
What are sand dunes
Large heaps of sand, form on dry backshore of a sandy beach.
40
What do sand dunes need to form
They need a
Large flat beach
Large supply of sand
A large tidal range so there is time for sand to dry.
An onshore wind to move sand to the back of the beach
An obstacle such as drift wood for the sand dune to form against.
41
Describe the formation of sand dunes
Sand continues to move up the windward slope
Height Builds up until the structure becomes unstable
The sand then slips down the leeward slope (side protected by the wind by an elevation)
42
Characteristics of Sand dunes
Gentle slope on windward side
Crests
Unstable steep slope on leeward side
43
Name the 6 types of dune in order from start
```
Embryo dune
Fore dune
Yellow dune
Grey dune
Dune slack
Mature dune
```
44
What is a dune slack
Where there is a trough of low point in a line of dunes
45
What is the leeward slope
Slope facing away from wind
46
What is the windward slope
Slope facing the wind
47
Name the 3 processes in which moves sand particles for sand dunes to form
Suspension
Saltation
Creep
48
What is suspension
Sand is picked up and carried by wind
| 1%
49
What is saltation
Grains of sand bounce along in the wind as they are alternately raised and dropped
(95%)
50
What is creep
Sand grains collide with eachother and push other grains along
(4%)
51
What is deposition (COASTAL)
Coastal deposition takes place in areas where the flow of water slows down. Sediment can no longer be carried or rolled along so has to be deposited.
It most commonly takes place in bays, where the energy of water is reduced when entering bay.
52
What is longshore drift
The transportation of sediments along the coast parallel to the shoreline.
The direction is determined by the prevailing wind e.g. A prevailing wind blowing from southwest causes a drift in an easterly direction.
Longshore drift travels the load in a zig zag fashion.
53
What is a spit
An area of sand or shingle which either extends at a gentle angle out to sea or which grows across a river estuary.
54
Requirements for a spit to form
Longshore drift moves large amounts of material along the beach
A sudden change in direction of the coastline
The sea relatively shallow and becomes progressively more sheltered.
55
Formation of a spit
Material is carried via longshore drift, a change in direction of coast line (from headland to bay) causes a sheltered area to form, the water at foot of headland is shallow so waves lose their energy and deposit material.
A prevailing wind causes the spit to curve inward forming a hook.
Behind spit in sheltered area forms a salt marsh
56
How does a bar form
A bar is formed when Lsd continues to deposit material onto spit as a result the spit extends across a bay joining up two headlands
57
How does a tombolo form
When a spit extends outwards into sea and connects to an offshore island forming a tombolo.
58
What is an offshore bar
Submerged or partly exposed ridges of sand or coarse sediment that is build by waves offshore from a beach.
59
How does an offshore bar form
When waves approach a gently sloping coast, friction between the waves and the sea bed causes the waves to break at some distance from the coast. Over time, more material are built up parallel to the coast to form a ridge of sand called offshore bar.
60
What are mudflats
Coastal wetlands that form when mud is deposited as water loses its energy as it gets closer to the coast. They are typically found in areas where the tidal waters flow slowly and somewhere that is sheltered e.g. Bays
61
What are saltmarshes
Area of coastal grassland and wetland that are flooded and drained by salt water brought in by the tides. Salt marshes form behind spits; the zone behind the spit becomes a sheltered area. The land is covered by water 2 times a day due to high and low tides.
62
Why do some cliffs collapse.
Marine processes, sub Ariel processes and mass movement.
63
What are marine processes
Hydraulic action and abrasion which erodes the base of the cliff, this results in the cliff face becoming steeper.
Undercutting the cliff also makes it unstable at the top
64
What are sub Ariel processes
Weathering such as freeze thaw action this weakens and fragments the rock
65
What is Mass movement
Loose rocks fall, slide or slump because of gravity
66
What is meant by rocks to "slide"
Large chunks of rock slide down slopes without any warning. This can be dangerous for people below cliff
67
What is meant by rocks that "slump"
Common when cliffs are made of clay, the clay becomes saturated during heavy rainfall and oozes down towards the sea as part of a mud or debris flow.
68
What are chemical processes
Includes solution. This occurs when water reacts with the calcium carbonate in rocks like limestone and chalk, the calcium carbonate dissolve and is washed away in solution
69
Mechanical processes
Freeze thaw action
Temperatures drop below freezing during the night and rise in the day. Any water held in cracks in the rock freezes, expands and then thaws again.
This is repeated till rock is weakened and fragments break away
70
What is cliff recession
Wave cut notch is formed and increases over time, this causes the cliff to collapse. The cliff retreats and a wave cut platform is left.
This is repeated
71
List some hard engineering strategies for protecting the coast
Sea wall
Groynes
Rock armour
Gabions
72
List some soft engineering strategies for protecting the coast
```
Beach nourishment
Beach re profiling
Sand dune regeneration
Managed retreat
Marsh creation
```
73
Define what is meant if the strategy beach nourishment is used
Adding sand and shingle from somewhere else to the beach
74
Define what is meant if the strategy beach re profiling is used
Reshaping of a beach using existing materials e.g. Moving shingle back up the beach
75
Define what is meant if the strategy sand dune regeneration is used
Creating or restarting sand dunes by either nourishment or planting vegetation to stabilise sand
76
Define what is meant if the strategy managed retreat is used
Removing all existing defences and allowing land behind it to naturally flood
77
Define what is meant if the strategy marsh creation is used
Breaking up of the waves and reducing their speed and erosive power
78
Benefits and costs of beach nourishment
```
Bigger beach - more room
Safe and natural
Protects expensive properties
BUT
during the process beach access is restricted for several weeks
Expensive to create - £300K dredger
```
79
Benefits and costs of beach re profiling
Cheap to maintain and easy to maintain
Natural
BUT
Bull dozers when created restrict access to Bach
Can be expensive e.g. £200,000 in West Sussex
80
Benefits and costs of sand dune regeneration
```
Help maintain and create habitats
Picnic areas
BUT
has to be checked twice a year with fertilisers
Expensive
Unstable
```
81
Benefits and costs of managed retreat
```
Encourages development of beaches
Cheap
Natural
BUT
People need to be compensated for loss and damage of land or buildings
Unsafe
```
82
Benefits and costs of marsh creation
```
Cheap
Low damage to environment
BUT
High maintenance
Cheaper housing may be flooded to protect expensive ones
Communities split up
```
83
Define what is meant if the strategy sea walls are used
Wall made out of hard material to reflect waves- concave shape
84
Define what is meant if the strategy groynes are used
Wooden or stone fences that are built to trap beach material transported by longshore drift
85
Define what is meant if the strategy rock armour is used
Boulders or large rocks that are piled up, usually as back of beach or in front of sea wall
86
Define what is meant if the strategy gabions is used
Wire meshed rocks and pebbles which can be stacked to form a wall like barrier at the back of the beach
87
Costs and benefits of using sea walls
```
Promenade on top
Long lasting
BUT
£5000 a metre are expensive
Not strong enough In some cases- a railroad on top of a sea wall once collapsed and cost £35 million in repairs
```
88
Costs and benefits of using groynes
```
Cheap
Last up to 40 years
BUT
act like barriers which impede walking
Trap sediments which restricts sediment down drift- uneven beach
```
89
Costs and benefits of using rock armour
```
Cheap
Quick to build
Long lasting
BUT
Restrict easy access to beach
Regular maintenance if storms occur
Eye sore
```
90
Costs and benefits of using gabions
```
Cheap
Easy to construct
BUT
if damaged can be a danger to human and animal
- birds caught in wire from cages
Easily destroyed
High maintenance costs
```
