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Coasts introduction


Coasts:

 Tsunamialarm in Alaska: 'Dangerous, destructive waves as possible' |A coast is a part of land which adjoins to or is near the sea. They are used by people in various ways which include fishing, industry, tourism and transport. Local residents, Councils and Environmental groups all have interests on how these areas should be managed and protected. This can lead to  a conflict or disagreement.

Waves:

Waves are created when the wind blows over the sea. The size and energy of these waves is dependent upon three factors:

-The fetch (which is the distance that the wave has travelled)
-The strength of the wind
-How long the wind has been blowing for

A long fetch (like one of 8,000 km) will result in a large powerful wave, whereas a short fetch of less than 200 km will produce a small wave.
The strength of the wind similarly affects the waves produced, and a larger wind force will produce bigger waves than a smaller one will. If the wind has been blowing for a longer period of time, the energy of the wave will increase as it has had a longer time to accumulate energy.

Destructive and Constructive waves:

Waves can either be constructive or destructive. This means that they affect the coastline differently.
When a wave reaches the shore, the water that rushes up to the beach is known as the swash and the water that flows back towards the sea is known as the backwash. The energy from the swash and backwash determine whether the wave type is constructive or destructive.
   
Destructive waves have a weak swash and strong backwash, which removes sediment from the      beach, and contributes to erosion. Destructive waves tend to be tall and to operate in storm conditions. However, Constructive waves operate in calm weather and tend to be less tall (usually     below 1m). The swash is strong and the erosion caused is limited.

Costal erosion

 Coastal erosion is a natural process in which sediment or rocks are washed away from the coastline, causing it to change shape. This process is a result of waves, tides or currents striking the shores.
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Erosion rates tend to increase when the waves are powerful which is common during storms or high winds. Harder rocks like igneous rock have slower erosion rates and form more dramatic rock formations over time, whereas sedimentary rocks like sandstone and chalk erode more easily and quickly. Where costal geology is softer, erosion can pose more of a risk for human settlements.

There are four types of coastal erosion:

Abrasion- when waves transport material which hits the cliffs and gradually wears them away

Hydraulic action- As waves approach the coast, they trap and force air into the gaps in the cliff. This eventually weakens the rock.

Attrition- Waves cause rocks to crash against each other, breaking them down into smaller rounder pieces.

Corrosion- Salts and acids within the seawater gradually dissolve the rock over thousands of years.

Erosion is a natural process and it threatens many coastal areas, however this doesn't prevent people from living by the sea. There are many reasons for this, including that the sea brings food and tourists to the area, which is beneficial to businesses. The sea also provides nice views and improves mental health and wellbeing for many people. Additionally, not all coastal areas are threatened by erosion, as some experience accretion, and even where erosion is present, it can be slowed and stopped with erosion walls, vegetation and other measures.

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