Coasts are shaped by the sea and the action of waves. Waves act in different ways, through the process of erosion, transportation and deposition.
A coast is found where the land meets the sea. Coasts undergo change due to coastal processes and (as with rivers) there are three main processes at work.
erosion
Transportation
Deposition
Waves- the power of waves is one of the most significant forces of coastal change
Waves are created by wind blowing over the surface of the sea. As the wind blows over the surface of the sea, friction is created, producing a swell in the water. The energy of the wind causes water particles to rotate inside the swell. This moves the waves forward.
The size and energy of a wave is influenced by:
the length of time that the wind has been blowing
The strength of the wind
How far the wave has travelled (called the fetch)
Destructive waves
operate in storm conditions
Are created from big, strong waves when the wind is strong and has been blowing for a long time
Occur when wave energy is high and the wave has travelled for a long time
Tend to remove material from the coast and associated with erosion
Backwash is stronger than swash
Constructive waves
operate in calm weather
Are less powerful waves
Break on the shore and tend to deposit material, building up breaches
Are responsible for transporting material
Swash is stronger than the backwash
Erosion
Erosion is the wearing down of the coast
Erosion occurs along the British coastline in the form of corrasion, attrition, corrosion, and hydraulic action.
Corrasion/ abrasion is when waves pick up beach material (e.g. pebbles) and hurl them at the base of a cliff.
Attrition is when waves cause rocks and pebbles to bump into each other and break up (becoming rounder and smaller)
corrosion/ solution is when certain types of cliff erode as a result of weak acids in the sea.
When waves hit the base of a cliff air is compressed into cracks. When the wave retreats the air rushes out of the gap. Often this causes cliff material to break away. This process is known as hydraulic action.
Coastal features created by wave action
Concordant and discordant coastlines
Discordant- alternating hard and soft rock at right angles to the coast
Concordant- hard and soft rock running parallel to the coast
Discordant coast
formed an Atlantic (discordant) coastline due to the softer rock being eroded quicker then the harder rock
Beaches form in the bays where the soft rock has been eroded away
Headlands of more resistant, hard rock are left behind
Weathering
Weathering is the breaking down of rocks, soils, and mineral through contact with the atmosphere. It is an ageing and decomposition process that takes place as a result of natural exposure.
What are the weathering processes?
9% volumetric expansion up freeing
Salt weathering
Ice segregation
Rock susceptibility to salt weathering
Landforms - tafoni, honeycomb weathering, gradual disintegration
Pressure release
Thermal expansion and contraction
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