GCSE GeographyUnit 2 – Natural EnvironmentTopic 1 – Coastal Landscapes

Lesson Aims:• Able to describe the characteristics

of destructive and constructive waves

Waves

• Waves are responsible for just about all the physical features and changes found along coastlines.

• So before we learn about these features and changes we have to get to grips with how waves themselves operate

Waves• Waves are usually formed by

the wind blowing over the sea. Friction with the surface of the water causes ripples which eventually develop into waves.

• The stretch of open water over which the wind blows is called the fetch

• The longer the fetch........• ...the more powerful the

wave can become.FETCH – the distance of open water over which the wind can blow

Waves• In open water, the waves takes on an orbital (circular) motion.• As waves approach the beach, the sea bed will eventually interrupt this circular

motion. • This makes the circular shape more of a oval shape (eliptical).• This pushes the crest of the wave upwards. It will eventually topple over onto the

beach.• The water then rushes up the beach = swash• And some water then flows back towards the sea = backwash

BACKWASH – the backward movement of water down a beach when the wave has broken

SWASH – the forward movement of a wave up a beach

Types of Waves

• There are two types of wave found at the coast

• Constructive waves• Destructive waves

Constructive Waves• Waves that surge up the beach with

a powerful strong swash• They have a weaker backwash• This means that they deposit (drop)

sediments (sand etc) on the beach• This deposition constructs a beach• Low energy• Therefore normally the reason for

extensive beaches

• They are well spaced out and longer than they are high and are usually found on gently sloping beaches

• Normally small waves

CONSTRUCTIVE WAVE - a wave with a strong swash and weak backwash, that surges up the beach

Destructive Waves• Names because they normally

destroy the beach through erosion• The backwash is much stronger

than the swash.• This means sand and pebbles are

carried away from the shore by the backwash

• These waves are higher than they are long

• High energy• Their destructive nature normally

creates steep beaches

• Normally larger waves that crash down onto the beach

DESTRUCTIVE WAVE – a wave with a powerful backwash and weak swash that crashes down onto the beach