Definitions of Coasts of Erosion and Coasts of Deposition
Coasts of erosion are coasts where erosion takes places. Erosional processes include abrasion, attrition, compression of air and hydraulic action. Erosional landforms include arches, blowholes, caves, cliffs, notches, stacks and wave cut platforms.
Coasts of deposition are coasts where deposition takes place. Depositional processes include bedload, long shore drift, saltation, solution, sorting and suspension. Depositional landforms include beaches, bays, coves, creeks, spits and tombolo.
The Factor Which Tend to Influence Whether Erosion or Deposition Takes Place
Processes that tend to influence erosional or depositional processes are:
Abrasion- the wearing away of the landscape by the sea armed with a load of debris.
Attrition- the wearing away of particles of debris, such as gravel, sand, or pebbles, as they bump against each other while being carried by the sea.
Bedload- the material bounced or rolled along the sea floor.
Compression of air- the process of air being forced into joints or bedding plains by a wave compressing the air so it is forced into the rock.
Fetch- the distance a wave has to travel between coast to coast. For example, the distance between the Caribbean and Europe.
Hydraulic action- the impact of moving water.
Long shore drift- when waves approach land at wide angle, so causing swash to occur at an angle and backwash to occur normally. Therefore debris is moved along a beach in a zigzag pattern.
Prevailing winds- the dominant wind direction of a region.
Rock type- the type of rock could be easily erodable (clay) or hard to erode (limestone).
Saltation- the bouncing of material from and along the sea bed or land surface.
Solution- the dissolving of a substance in water.
Suspension- Material hanging in the water.
Tidal range- the average difference between high and low tides in a given location.
Type of wave- the plunging type of wave causes more erosion than the spilling type. This is because the backwash is greater than the swash on a plunging type, and visa-versa for the spilling type.
Landforms created by these processes are:
Arches- when two caves meet.
Bays- indentations in the coastline with a headland on either side.
Beaches- strips of land sloping gently toward the sea.
Blow hole- when compressed air is released through a hole in the ground, caused by the air making its way through joints and bedding planes.
Caves- holes in the rock wall.
Cliffs- steep walls of rock, usually facing the sea.
Coves- small bays.
Creeks- small inlets of the sea.
Spits- ridges of sand running away from the coast.
Stacks- where arches have collapsed.
Tombolo- where islands are joined to the mainland by a bar.
Wave cut platforms- where notches and marks are made by waves.
Coasts of Erosion
The definitions of processes of erosion are as follows:
Abrasion: the wearing away of the landscape by the sea armed with a load of debris.
Attrition: the wearing away of particles of debris, such as sand, gravel, or pebbles, as they bump against each other while being carried by the sea.
Compression of air: when air is forced into rocks by waves and compressed, resulting in high-pressure in the joints and bedding-planes of rocks.
Hydraulic action: The impact of moving water, a strong erosive force.
Solution: the wearing away of the coast as material dissolves.
How erosional landforms are formed:
Arch: when two caves develop on either side of a headland and meet. See cave.
Blowhole: where a joint extends from the bottom of a cliff to the top. When air is forced through this joint by compression of air and hydraulic action, then the air rushing through the joint makes a blowhole.
Cave: develops along a line of weakness along the base of the cliff, which has been subjected to constant compression of air by hydraulic action.
Cliff: cliffs are caused by undercutting, a form of hydraulic action. The undercutting continues to gnaw into a hillside, which causes a steep rock wall.
Cliff fall: when undercutting has cut underneath the cliff, there is no foundation for the overlying rock, so the cliff collapses.
Cliff retreat: when processes of erosion, such as weathering and undercutting, combine to force the cliff towards land by eroding away at the rocks.
Notches: marks left behind by process of abrasion.
Stack: where an arch has collapsed. See arch and cave.
Wave cut platforms: where notches and marks are made by abrasion.
Note: the diagrams for this question can be found on a separate sheet.
Coasts of Deposition
The processes of transportation are as follows:
Bedload: the material that is rolled or bounced along the bottom.
Long shore drift: when waves approach land at wide angle, so causing swash to occur at an angle and backwash to occur normally. Therefore debris is moved along a beach in a zigzag pattern.
Saltation: the bouncing of material from and along the sea bed or land surface.
Solution: the dissolving of a substance in water.
Suspension: material hanging in the water.
Tidal action: the rotational movement of waves as they travel and break.
How depositional landforms are formed:
Bay: indentations in the coastline with a headland on either side. Caused by long shore drift and tidal action.
Beach: strips of land sloping gently toward the sea. A beach is caused by all depositional processes.
Cove: small bays. See bay.
Creek: small inlets of the sea. Inlets are caused by the joint connecting a cave and a blowhole collapsing.
Spit: ridges of sand running away from the coast. Offshore banks of beach-type material being deposited form a spit.
Storm beach: shingle thrown up above the high water mark by stormy waves.
Tombolo: where islands are joined to the mainland by a bar. See spit.
Defences Against The Sea
Sea wall-
Cost: �6000 per metre.
Technique: Concrete wall that reflects waves and withstands waves breaking on it.
Advantages: Good defence against waves.
Disadvantages: A blight on the landscape.
Rip-Rap-
Cost: �3500 per metre.
Technique: Breaks up the waves when they smash against it.
Advantages: Cheaper than sea walls and less of a blight on the landscape.
Disadvantages: Easier to erode than sea walls.
Revetment-
Cost: �2000 per metre.
Technique: Concrete that like a beach that is not erodable.
Advantages: Harder to erode than beach rebuilding, lasts longer.
Disadvantages: Useless against powerful waves and a blight on the landscape.
Beach Rebuilding-
Cost �3 per cubic metre.
Technique: Replaces lost sand.
Advantages: Cheap in the short term and natural.
Disadvantages: Easy to erode, requires frequent replenishment.
Gabions-
Cost: �100 per metre.
Technique: Strong wire baskets filled with sand and stone; rather like a more natural looking revetment.
Advantages: More natural looking than a revetment.
Disadvantages: Easier to erode than revetment.
Groynes-
Cost: �10000 each situated 200 metres apart. (Cost per metre = �50)
Technique: Traps sand therefore reducing erosion.
Advantages: Cheapest of sea defences.
Disadvantages: Makes the far side more prone to erosion due to no replenishment of sand.
Offshore Breakwater-
Cost: �5000 per metre.
Technique: The wall protects the shore from all waves.
Advantages: Cheaper than a sea wall and just as effective.
Disadvantages: A blight on the landscape and may be a hazard to ships/boats.
Uses of Coasts
Man can use the coast in a number of ways. A large seaside resort could be built, such as Blackpool. This would require extensive road networks to ensure that traffic was not a major problem. The large numbers of people would cause lots of pollution in the town in a number of ways. There would be a lot of litter, as well as the problems caused by more waste. Then there are the local people, who will not like the noise and nuisance caused by the tourists.
A port could be built to serve a large city. This would handle passengers and goods. Again, road networks would have to be built to ensure free flow of traffic. Also, the estuary would have to be dredged to enable ships to sail in there.
A marina for sailing enthusiasts and those who participate in water sports could be built. This would require a large amount of water for the marina itself, as well as car parks for the participants.
A naval base could be built. This would require a large sheltered harbour, which is easy to defend. The locals will not like the military traffic going through their town.
An oil refinery could be built. This would mean building jetties for the large oil tankers and would require roads for tanker lorries to collect and distribute the oil.
An oil-fired power station could then be built to power the town. This would cause pollution and would blight the coastal landscape.
If the town was big enough, an airport could be built for commuters to travel to the big cities and for tourists to come to the resort.