How do waves influence erosion?

Key questions:

• What are constructive + destructive waves?• How do waves influence erosion?

How do waves work?

What causes waves?

How do waves work?

• Waves are created by wind• The friction of the wind makes the

sea swell and rise up• The energy of the wind causes water

particles inside the sea to rotate and this movement pushes the wave forward

• The waves get bigger until they reach the coast where they break

Waves

Coastal processes

• Bitesize coastal processes

Geog.GCSE

• P88

• Make a large, neat copy of the diagram on p88.

• Add short labels

The sea drains back down the beach.

This is called backwash.

This process moves material back down the

beach.

Within each individual wave, the water

particles all move in a circular motion. A

constant circle back to their starting points.

When a wave moves in to shallow water near the coastline it starts to rear up and distort

until it breaks.

Out at sea, sometimes thousands of miles away, the wind is

blowing.

As the wind blows across the surface of

the sea it creates friction.

It tugs across the sea and causes the wave

shape to move forwards.

Once the wave breaks, there is energy moving

and also water crashing forwards.

This provides the energy for erosion and

deposition.

Water from the sea rushes up the beach.

This is called the swash.

This process moves material up the beach.

The sea drains back down the beach.

This is called backwash.

This process moves material back down the

beach.

Within each individual wave, the water

particles all move in a circular motion. A

constant circle back to their starting points.

When a wave moves in to shallow water near

the coastline it starts to rear up and distort until

it breaks.

Out at sea, sometimes thousands of miles away, the wind is

blowing.

As the wind blows across the surface of the

sea it creates friction.

It tugs across the sea and causes the wave

shape to move forwards.

Once the wave breaks, there is energy moving and also water crashing

forwards.

This provides the energy for erosion and

deposition.

Water from the sea rushes up the beach.

This is called the swash.

This process moves material up the beach.

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Waves keywords

• Swash = the wave washing up the beach.• Backwash = the wave pulling back down

the beach by gravity.• The crest = is the top of the curling wave,

the wave at its highest point.• The fetch = is the distance a wave travels

before it crashes on to the coastline.• A constructive wave = helps to build a

beach.• A destructive wave = erodes a beach.

Why are some waves stronger than others?

Geog.gcse p88. Complete these Qs in sentences.

1. The height and strength of waves depend on i)................ii)................iii)...................

2. What is the ‘fetch’?3. What winds affect our south coast in Britain?4. South-westerly winds produce .......................

waves because ...........................5. South-easterly winds

produce .............................. waves because ...........................

6. What is more important, fetch or wind speed?

Fetch

Brazil

Atlantic Ocean

France

English channel

Why do waves break?

• Why do you think waves break when they reach a beach?

Characteristics of Waves

crest

Fetch

Waves

• There are two main types of waves:• Constructive vs Destructive

Constructive vs Destructive

• Geog.gcse p89 or Tomorrow’s Geog p5

• Copy the diagrams of the two types. • You must include the information too

Constructive Waves

Gently sloping wave

Wave crests far apart

Breaking wave spills, does not crash

Gentle beach

Destructive Waves Steeply sloping wave

Breaking wave plunges + crashes

Waves close together

Quick test

• Which waves builds up the beach?• Which wave has a stronger backwash?• Which wave has low wave height?• Constructive waves usually happen on

gentle or steep slope beaches? Why?• Destructive waves are ‘spilling’ or

‘breaking’?

Waves + the coast

• Not only do waves erode the coast, they also transport and deposit the material that they erode to different places

• Southsea beach may have been eroded and transported there from France

• How do waves transport material?

Long-shore drift (LSD)

Exam Q

1) Describe and explain how constructive and destructive waves work. Use keywords or examples where possible. [4marks]

2) Apart from the strength of waves, what other factors can effect how quickly a coastline erodes? [3marks]