Coasts Flashcards
What is attrition
Rocks knock against each other wearing each other away
What is abrasion
Fragments of rock being picked up and hurled by the sea at a cliff
4 types of transportation
Solution, traction, suspension, saltation
What is traction
Rocks rolling along sea bed
What is saltation
Rocks bounced along sea bed
Types of mass movement
Rock fall , mud flow , slumping , landslide
Factors that determine wave size
Strength of wind
Fetch
Length of time the wind blows
Differences between constructive and destructive waves
Constructive = low energy, slash stronger than backwash, deposition greater
Destructive = high energy, backwash stronger than swash, erosion greater
3 types of weathering with examples
Biological = animals burrowing in rocks
Physical / mechanical = freeze thaw, water freezing in cracks in rocks then melts and breaks rock
Chemical= oxidation, oxygen breaking down rocks over time
What is concordant coastlines
Have the same type of rock along its length
Tend to have fewer bays and headlands
Such as lulworth cove
What is discordant coastlines
Where the rock alternates bands between hard and soft rock
What is a tombolo
Ridge of sand or shingle connecting an island to mainland
What is a bar
Where a spit extends fully across a bay and connects two pieces of land together
Form a lagoon behind it
What is example of soft rock
Clay and sand
Example of soft rock
Clay and sand
Example of hard rock
Chalk
What is rockfall (mass movement)
When the cliff materials break and crumble down the cliff
What are landslides (mass movement)
Large blocks of rock slide downhill
What are mudflows (mass movement)
Saturated soil (soil filled with water) flows down a slope.
What is slumping (mass movement )
Large area of land moving down the slope, it leaves behind a curved indented surface
Formation of bar and spit (4 marks)
Longshore drift follows the direction of the prevailing wind. It usually hits the coast at an oblique angle. The swash carries material up the beach in the same direction as the waves. The backwash then carries material down the beach at a right angle back towards the sea. Over time, material zig zags along the coast. Spits form at a sharp bend in the coastline. Spits form when the coastline suddenly changes shape, sand starts to build up in the sheltered side of the headland . A spit will continue to grow until the water becomes too deep or until material is removed faster than it is deposited. Wave refraction carries material round into more sheltered water which forms a hook. Can form a salt marsh behind it. Longshore drift may cause a spit to grow across a bay causing a lagoon to form behind it. This feature is called a bar.
Advantages and disadvantages of rock armour (rip rap)
A= disperses the energy of the waves and reduces their erosional power. Structure is quick to build and easy to maintain. Much cheaper than a seal wall. If well maintained it can last a long time. It is versatile as it can be placed in front of sea wall to lengthen its lifespan or used to stabilise slopes on sand dunes. Often used for fishing.
D=access ri beach is difficult as people have to climb over rock armour. Cost may be high especially when it has to be imported. Can look unattractive
Advantages and disadvantages of groynes
A=designed to stop material moving along the beach by Longshore drift they work by building up amount of sand on the updraft side. They create wider beaches with is popular for tourists and boost local economy. Reduces risk of damage making residents and local businesses fell more secure. Not too expensive. If well maintained can last up to 40 years
D= beaches downdrift are starved of beach material due to their impact on Longshore drift this leads to increased erosion which has economic impact further along coats. Need regular maintenance as they can rot.
Advantages and disadvantages of sea walls
A= effective in protecting cliffs from erosion and also act as a barrier to prevent flooding, deflect wave energy back to sea, give people sense of security. Often have a promenade of too which doubles up as a cycle route -could attract tourists. If well maintained could last for years. Do not impede the movement of sediment downdrift so do not disadvantage other areas
D= very expensive to construct and maintain (over 5000 pound per metre), recurved sea walls can increase the erosion of beach material and may destroy habitats
What is hydraulic action
Power of the waves as they smash onto a cliff. Trapped air is forced into holes and cracks in the rock, eventually causing the rock to break apart
How is a wave cut platform formed
Waves cause most erosion at the foot of a cliff, this erosion forms a wave cut notch which is enlarged as erosion continues. The rock above the notch becomes unstable, and eventually collapses. The collapsed material is washed away and a new wave cut notch starts to form. Repeated collapsing results in the cliff retreating. A wave cut platform is the surface that’s left behind as the cliff retreats. Pebbles grind over the rocky platform often causing it to become smooth. IF NEEDED TO DRAW DIAGRAM LABEL: HIGH TIDE, LOW TIDE LEVEL, RETREATING COASTLINE, PREVIOUS POSITION OF CLIFF, CURRENT POSITION OF CLIFF
Advantages and disadvantages of gabions
A= cheap to produce and flexible in final design, can improve drainage of cliffs, will eventually become vegetated and merge into landscape, much cheaper than other hard engineering strategies, last 20-25 years
D= wire basket may be subject to heavy wear and tear by abrasion or could rust, hard to install require large equipment, eye sore so can put of toustists visiting pretty heach
Advantages and disadvantages of beach nourishment (adding of sediment to beach)
A= usually looks natural and can improve attractiveness of coast so increased tourism, relatively cheap, easy to maintain
D= requires constant maintenance to replace beach material as it is washed away. People may be prevented from using beach for several weeks during maintenance. Costs up to 500,000 per 100 meters
What is dune regeneration
artificial creation of new dunes of restoring existing dunes using strategies such as marram grass or fencing them off from humans
Advantages and disadvantages of dune regeneration
A= sand dunes act as a physical barrier between the sea and the land, they absorb wave energy and in doing so protects the land from the sea, increase biodiversity providing a greater range of natural habitats for plants and animals.
D= can be easily damaged by storms and it can time consuming to plant the grass and maintain the area and can also deter tourists. Costs 400-2000 per 100 metres
Formation of headland and bays (4 or 6 marks)
Formation of head lands and bays changes over time due to differences in resistance of rocks to erosion, some parts of coast may retreat faster than others. Discordant coastline is when it is alternated bands of soft and hard rock. The soft less resistant rock will be eroded quicker than the harder more resistant rock and differences become more pronounced. Eventually there will be headlands that stick out into the sea and bays where the land has been worn back. The headlands are more exposed to wave attack and erosional landforms develop. Due to wave refraction the energy of the waves is focused on the headlands and spread out into the bays.
