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Coast by Mind Map: Coast

1. Erosion, Transportation and Deposition

1.1. Erosion: the wearing away of rock and soil

1.1.1. There are four main types: Hydraulic action, Solution, Abrasion and Attrition Attrition is where the rocks wear each other down into smaller and smaller pieces Hydraulic action is where the water forces itself into the rock. This helps break up the rock Solution is where soluble materials in the rock dissolve in the water Abrasion is where the water flings rock and sand at the cliff or rock formation and uses brute force to chip away at it.

1.2. Transportation: The carrying away of eroded materials

1.2.1. Long shore drift is a type of transportation that is manly found at the coast Many costal towns build defenses called groynesto slow down long shore drift to keep the beach there.

2. Costal landforms

2.1. The type of rock that the coast is made of effects the shape of the coastline

2.1.1. Hard rock is hard to erode, but can support itself Hard rock forms cliffs that jut out forming a headland Hard rocks include granite and slate

2.1.2. Softer rock can erode quicker and cannot support itself They get eroded leaving a protected bay Sandstone and clay are types of soft rock

2.2. Wave-cut platforms

2.2.1. Waves carve notches in cliff until the the overhang falls into the sea.

2.2.2. The process continues and then the cliff recedes and goes back.

2.3. Caves, arches and stacks

2.3.1. The sea erodes cracks in the headland and turn into caves

2.3.2. When the caves gets eroded all of the way through it becomes an arch.

2.3.3. After time the arch collapses leaving and stack. In time, the waves erode the stack to a stump

2.4. Spits and Salt marshes

2.4.1. Head lands interrupt long shore drift and so sand and shingle are deposited in the sea.

2.4.2. This builds up and makes a spit If this touches an island it becomes and tombolos

2.4.3. The end of the spit becomes curved because of the waves. This is called a hook

2.4.4. Silt and mud may build up because it is sheltered by the spit. This would become the salt marsh. Salt marshes are a great habitat for wildlife

3. Waves

3.1. Waves are formed from friction of wind against the water

3.2. There are factors that effect the largness of the waves

3.2.1. The longer the fetch, the length of water that the wind blows over, the larger the waves

3.2.2. The stronger the wind means more energy put into the waves

3.2.3. The longer the amount of time means there is more time for the waves to build up

3.3. At the shore the waves break

3.3.1. This causes swash, which rushes up the beach

3.3.2. The water that goes back to the sea is called backwash.

3.4. Constructive and destructive waves

3.4.1. If the swash is more powerfull that the backwash it causes constructive waves Constructive waves push beach material onto the beach and help build the beach Constructive waves have unique characteristics, for example, they are evenly spaced

3.4.2. If the backwash more powerful than swash it causes a deconstructive wave The waves eat at the land, dragging the pebbles and sand away.

4. Tides

4.1. The tides are caused by the moon and the sun

4.1.1. The main 'puller' is the moon as the sun is much farther away

4.2. As the moon orbits the earth, it attracts the sea and pulls it upward. The rise and fall of the sea gives us tides

4.3. High tides happen about every 12.5 hours, with the low tides between

4.4. The drop in the sea level is called the tidal range.

4.4.1. This changes throughout of the year as the aliment of the moon and the sun means that the water gets pulled more. When the moon allines with the sun we get a spring tides so the pull is magnified

5. Costal defences

5.1. The types of costal defenses are divided up into 2 groups. Hard and soft engineering

5.1.1. Hard engineering: Hard engineering options tend to be expensive, short-term options. They may also have a high impact on the landscape or environment and be unsustainable. Sea walls: A wall built on the edge of the coastline. Pros: Protects the base of cliffs, land and buildings against erosion. Can prevent coastal flooding in some areas. Cons: Expensive to build. Curved sea walls reflect the energy of the waves back to the sea. This means that the waves remain powerful. Over time the wall may begin to erode. The cost of maintenance is high. Groynes: A wooden barrier built at right angles to the beach Pros: Prevents the movement of beach material along the coast by longshore drift. Allows the build up of a beach. Beaches are a natural defense against erosion and an attraction for tourists. Cons: Can be seen as unattractive. Costly to build and maintain. Rock armour: Large boulders are piled up on the beach. Pros: Absorb the energy of waves. Allows the build up of a beach. Cons: Can be expensive to obtain and transport the boulders.

5.1.2. Soft engineering: Soft engineering options are often less expensive than hard engineering options. They are usually more long-term and sustainable, with less impact on the environment Beach management This replaces beach or cliff material that has been removed by erosion or longshore drift. The main advantage is that beaches are a natural defence against erosion and coastal flooding. Beaches also attract tourists. It is a relatively inexpensive option but requires constant maintenance to replace the beach material as it is washed away. Managed retreats Areas of the coast are allowed to erode and flood naturally. Usually this will be areas considered to be of low value - eg places not being used for housing or farmland. The advantages are that it encourages the development of beaches (a natural defense) and salt marshes (important for the environment) and cost is low. Managed retreat is a cheap option, but people will need to be compensated for loss of buildings and farmland.