Coasts

Created by

Mya

Cards (35)

How are waves created?
Waves are created by wind blowing over the surface of the sea. As wind blows over the sea, friction is created producing a swell in the water.
Properties of a destructive wave
They have a strong backwash compared to their swash
They are high in, relation to their length
The form frequently, the break at a rate of around 15 waves per minute
Properties of constructive waves
They have a weak backwash compared to their swash
They are long in, relation to their height
They are gentle, they break at a rate of 6 to 9 waves per minute
What is hydraulic action?
The sheer force of the waves crashing on the shore
What is abrasion/corrasion
Waves bring with them bits of rock and sand.
These grind down cliffs like the action of sandpaper
What is attrition?
Waves cause rocks and pebbles on the shore to collide into each other and breakdown and become smaller, smoother and more rounded
What is corrosion/solution
Acids contained in seawater will slowly dissolve certain types of rock such as chalk or limestone.
How are wavecut platforms formed?
Weather weakens the top of the cliff
The sea attacks the base of the cliff forming a wavecut notch (hydraulic action and corrasion)
How are wavecut platforms formed?
Weather weakens the top of the cliff
The sea attacks the base of the cliff forming a wavecut notch (hydraulic action and corrasion)
The notch increases in size causing the cliff to collapse
The backwash carries the rubble towards the sea forming a wavecut notch
The process repeats itself and the cliff continues to retreat
How is a stump formed?
A large crack, opened up by hydraulic action
The crack grows into a cave by hydraulic action and abrasion
The cave becomes larger
The cave breaks through the headland forming a natural arch
The arch is eroded and collapses
This leaves a tall rock stack
The stack is eroded forming a stump
What is solution?
Minerals are dissolved in sea and carried in solution. The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution
What is suspension?
Small particles are carried in water which can make water look cloudy.
What is saltation?
Load is bounced along the seabed in a leapfrogging motion (shingle or sand)
What is traction?
Pebbles and larger sediment are rolled along the sea bed
What is longshore drift?
The direction of the prevailing wind so material is moved that way
(south-west for Britain)
What is coastal deposition?
When the sea loses energy, it drops its load of sand, rock particles and pebbles, which it has been carrying
When does coastal deposition happen?
When the swash is stronger than the backwash and is associated with constructive waves
How are spits formed?
Prevailing wind is from south west so material carried eatwards
Sand and shingle are deposited as water is sheltered by headland
The material continues to build upwards and outwards forming a spit
when winds blow from a different direction the waves will force the material to be pushed inland forming a curve at the end of the spit (hooked spit)
Why are coastal defences needed?
Half the worlds population(around 3.2bil)live within 200km of the sea
By 2025 it is estimated that around 6 billion people will live in coastal areas
What are the four main land uses in coastal zones?
Residential
Tourism
Transport
Industry
What is a seawall?
A concrete wall built on the edge of the coastline.
It reflects waves back out to sea preventing erosion of the coast.
Also acts as a barrier to prevent of the waves.
An advantage of seawall?
Gives good protection of cliffs, lands and buildings.
A disadvantage of seawalls?
Expensive to build £7million per sq km, cost of maintenance is also high
What are gryones?
A wooden barrier built at right angles to the beach to prevent sand moving along the beach. They are built about 200 metres apart. They trap beach material transported by long shore drift. This creates wide beaches, which slows the waves and reduces their energy
An advantage of gryones?
Allows build up of a beach
A disadvantage of gryones?
Seen as unattractive. costly to build and maintain
What are gabions?
A gabion is a metal cage measuring 1m by 1m that is built on site from 6 metal mesh sides and then filled with rock. They are cages of stones used to protect the beach. They are piled up on the beach which protect the coast by breaking up the waves
An advantage of gabions
Absorbs the energy of the waves
A disadvantage of gabions
Seen as unattractive and make beach access difficult. They can rust and be damaged by storms
Rip-rap (rock armour)
Large boulders and concrete blocks are piled up on the beach which protect the coast by breaking up the waves
An advantage of rock armour
Absorbs the energy of the waves
A disadvantage of rock armour
Seen as unattractive and make beach access difficult
What is beach rebuilding/nourishment (soft engineering)
Adding more sand or shingle to the beach. This replaces beach or cliff material that has been removed by erosion or longshore drift.
An advantage of beach rebuilding
Beaches are a natural defence against erosion and coastal flooding. Beaches also attract tourist
A disadvantage of beach rebuilding
It is an expensive option (£1mill per mile) and requires constant maintenance to replace the beach material as it is washed away