Flashcards in Waves Deck (11)
Name four measurements of a wave
Height, Crest, Trough and Wavelength
What causes waves?
When wind blows over water, there size is related to wind speed and builds up over time (storm waves increase over several days) wind creates frictional drag which produces movement in the upper surface of the water. Water molecules move in a circular orbit as waves moves across the surface.
What happens when waves approach the coast?
- water becomes shallower so the circular orbit changes to elliptical
- the wavelength and viscosity decreases but the wave height increases causes water to back up behind
- force pushes the wave higher so it becomes steeper before plunging against the shore
- swash and backwash
Describe constructive waves
- 6-9 per minute
- Swash deposits larger material at the top of the beach creating a berm of shingle
- As the berm increases, the backwash weakens so only moves smaller material
Describe destructive waves
- More frequent in winter but general frequency is 11-16 a minute
- Berms are eroded by plunging waves and high energy swash
- Strong backwash transports sediment offshore
- Sometimes exerts a current known as a rip or undertow which drags sediment to the next wave
Where in the UK are waves highest?
West of Ireland
Where in the UK are waves the lowest?
Surrounding England but high waves off the south-west shore and south of Ireland
What are tides?
The periodic rise and fall of the sea surface produced by the gravitational pull of the moon
How does the moon control the tides?
It pulls water towards it to create a high tide which as a result creates a compulsory bulge on the opposite side of the Earth and between which is low tide
When will the highest tides occur?
When the moon, sun and earth align so the gravitational pull is strongest which happens twice every lunar month and results in spring tides with a great tidal range