Coastal processes

What is the size and energy of a wave influenced by?

- how long the wind has been blowing - the strength of the wind - how far the wave has travelled (the fetch)

There are four ways that waves and tidal currents transport sediment. These can then contribute to the movement of sediment by longshore drift. What are the ways?

- solution - suspension - saltation - traction

What are the ways in which destructive waves erode the coastline?

Hydraulic action, abrasion, attrition and solution

Where does the material in the sea come from?

Various sources: - eroded from cliffs - transported by longshore drift along the coastline - brought inland from offshore by constructive waves - carried to the coastline by rivers

How are waves created?

Waves are created by wind blowing over the surface of the sea. As the wind blows over the sea, friction is created - producing a swell in the water. The energy of the wind causes water particles to rotate inside the swell and this moves the wave forward.

What is transportation?

Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is called transportation.

What is attrition?

Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.

What is deposition?

When the sea loses energy, it drops the materials (sand, rock particles and pebbles) it has been carrying.

When does deposition happen?

When the swash is stronger than the backwash

What is stronger in a constructive wave, swash or backwash?

With a constructive wave, the swash is stronger than the backwash.

What is stronger in a destructive wave, swash or backwash?

With a destructive wave, the backwash is stronger than the swash.

What is the swash?

The water flowing towards a beach when a wave breaks.

What is the backwash

The water flows back down the beach (at 90 degrees) to the sea after the wave has broken - this is called the backwash.

What is coastal erosion?

The wearing away and breaking up of rock along the coast

How do constructive waves affect the shore?

They break on the shore and deposit material, building up beaches.

Describe a constructive wave.

They have a long wavelength, and are low in height.

Describe a destructive wave.

They have a short wave length and are high and steep.

How are destructive waves created?

They occur when the wind is powerful and has been blowing for a long time, when wave energy is high and the wave has travelled over a long fetch.

How do destructive waves affect the coast?

They tend to erode the coast.

What is solution?

Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

What is hydraulic action?

Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.

What is abrasion?

Bits of rock and sand in waves grind down cliff surfaces like sandpaper.

In what weather are constructive waves created?

Constructive waves are created in calm weather.

What is longshore drift?

Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.

In what conditions are destructive waves created?

Destructive waves are created in storm conditions.

Which type of waves are more powerful, destructive or constructive?

Destructive.

What is saltation?

Load is bounced along the sea bed, e.g. small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods.

What is solution?

Minerals are dissolved in sea water 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 traction?

Pebbles and larger sediment are rolled along the sea bed.

What is suspension?

Small particles are carried in water, eg silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves.