Waves Flashcards
What are waves important for?
They are a method of moving energy, which ultimately erodes and shapes coastlines.
How are waves generated?
- Wind speed is slower at the surface of water due to friction between air and water.
- Friction produces turbulence in air at the waters surface, also transferring energy into the water.
How does WIND effect waves?
Faster wind -> more kinetic energy -> larger waves
How does TIME effect waves?
Long wind blow -> more time for energy transfer -> stronger waves
How does the FETCH effect waves?
Longer fetch -> more opportunity to transfer energy to water -> stronger waves
Crest…
Highest point of a wave
Trough…
Lowest point of a wave
Amplitude…
Height from stationary water to crest
Wave height…
Height from trough to crest
Wavelength…
Horizontal distance between trough and trough/crest and crest
Time period…
Time take for wave to travel one wavelength (s)
Frequency…
Number of crests/troughs passing one point per second
Velocity…
Speed the wave travels
Wave speed
What is the ratio of height:wavelength that waves become unstable and break?
7:1
What happens as waves approach the coast?
Water gets shallower, waves get bigger, energy being carried reaches the land.
What happens in the process of SHOALING?
Water becomes shallow, forcing wave to slowdown due to increase in friction. As it slows, wavelength decreases and height increases. The ratio is reached and the wave becomes unstable and breaks.
Features of a Constructive Wave
- Long period
- Long wavelength
- Low amplitude (relatively calm)
- Strong swash
- Weak backwash
Role of a Constructive wave
Deposit more material than they remove therefore build up gentle beaches.
Development of berms due to repeated action of pushing material up a beach.
Features of a Destructive Wave
- Short period
- Short wavelength
- High amplitude
- Steep profile (particularly during storms)
- Weak swash
- Strong backwash
Role of a Destructive Wave
Remove more material from a beach producing a steep beach with breakpoint bars.
In stormy weather, material can get thrown to the back of the beach due to higher energy waves producing a STORM BEACH (ridge of coarse material)
When does Wave Refraction take place?
As a wave approaches an irregular coastline.
Why are waves slowed during Wave Refraction?
As waves approach a coastline, waves are slowed by friction as the water shallows approaching the headland.
Which areas of the wave move faster and why?
The part of the wave in deeper water approaching the bay moves faster as it is not slowed by friction.
What occurs around the headland?
Waves refract around the headland and the orthogonal converge.
What occurs around the bays?
Orthogonal diverge and energy is dissipated leading to deposition.
What occurs as a result of Wave refraction?
- Waves become increasingly parallel to the coastline.
- Headland receives a concentration of wave energy and therefore erosion takes place.
- Wave breaks on the side of the headland at an angle, therefore there is longshore movement of eroded material into bays.
