Sources of energy at the coast

How do waves form?

waves are created by the wind - the friction caused by the movement of the wind creates a circular orbit in open water, causing a vertical movement in the water

What is the average ocean depth?

3.5km (2.3 miles)

What happens when a wave reaches the coast?

1. the wind causes friction at the surface of the water, which creates waves

2. the waves move in a circular motion

3. friction occurs between the base of the wave and the sea bed, causing the wave to become elliptical in shape

4. when a wave moves into shallow water near the coast, it is distorted until it “breaks”

wave refraction

the distortion of wave fronts as they approach an indented shoreline

fetch

the maximum length of open water over which the wind can vlow unobstructed to generate waves

What affects the size of waves?

• strength of the wind blowing over the sea

• duration of the wind

• length of open water over which the wind is blowing (fetch)

What are the characteristics of destructive waves?

• high waves

• short wave length

• tail breakers

• weak swash 

• strong backwash

• long fetch

• greater erosion

• 11-15 per minute wave frequency 

• strong winds

• high energy 

What are the characteristics of constructive waves?

• low waves

• long wave length

• strong swash

• weak backwash

• 6-9 per minute wave frequency 

• low energy

• weaker winds

• greater deposition 

• short fetch

What are the characteristics and typical landforms of a high-energy coastline?

• rocky

• erosion exceeds deposition

• headlands

• cliffs

• wave-cut platforms

What are the characteristics and typical landforms of a low-energy coastline?

• sandy

• deposition exceeds erosion

• beaches

• spits

• coastal plains