Waves - sources of energy Flashcards
How do waves move?
Waves move as kinetic energy moves through the water in a circular motion as it rotates in a fixed position.
What are some key characteristics of destructive waves?
-Berm may change shape
-11-15 waves per minute
-1m high+ and 20m short wavelength
-larger longshore (breakpoint) bar
-little water loss through percolation
-gradient decreases down the beach
What are some key characteristics of constructive waves?
-lots of water lost through percolation
-less than 1m high and up to 100m in wavelength
-6-9 waves per minute
-sediment moves up the beach to form a berm
-flat and gentle wave
How are waves formed?
1.Wind moves across the surface of the water, causing frictional drag and forming a circular orbital motion of water particles in the ocean (oscillatory waves)
2.As the seabed becomes shallower at the coastline, the orbit of the water particles becomes more elliptical resulting in a more horizontal movement of the waves (translatory waves).
3.The wave height increases but the wavelength and wave velocity both decrease.
4.Water backs up from behind the wave until the wave collapses and surges up the beach.
What are the three factors affecting wave energy?
1.Strength/speed of the wind
2.Duration of the wind
3.Size of the fetch
How does the strength/speed of the wind affect wave energy?
- The larger the pressure gradient of the air, the stronger the winds. The stronger the wind, the greater the friction on the surface of the water and the bigger the waves.
2.The faster the wind travelling over the water surface, the bigger a wave will be.
How does the duration of the wind affect wave energy?
The longer the length of time the wind is in contact with the water, the larger the wave will be.
How does the size of the fetch affect wave energy?
The larger the fetch (distance over which the wind blows) the more powerful the waves will be.
Why may the types of waves in a coastal environment vary?
- In summer, constructive waves are dominant but destructive waves are dominant in winter.
-When a storm occurs, constructive waves may become destructive waves.
-Climate change may increase the storm frequency in the UK.
-Coastal management may affect the type of waves that occur.
What is the gradient of the beach like in winter?
A steeper gradient.
What is the gradient of the beach like in summer?
A gentler gradient
Explain the negative feedback cycle which takes place along a coastline throughout the year?
1.Constructive waves cause deposition on the beach, resulting in the beach profile getting steeper.
2. The steeper gradient causes destructive waves to form.
3.Destructive waves erode the beach, resulting in the beach profile getting shallower.
4.The shallower gradient causes constructive waves to form.
What are oscillatory waves?
Waves with a circular orbit and short wavelength
What are translatory waves?
Waves with an eliptical orbit and longer wavelength
Why do waves break?
- The prevailing wind moves across the surface of the water, causing frictional drag so waves with a short wavelength begin rotating in a circular orbit (oscillatory waves).
-As waves move closer to the shoreline and the seabed becomes shallower, eventually friction at the base of the wave slows it and causes it to become eliptical in orbit (translatory waves form)
-The wave height increases, but the wavelength and wave velocity both decrease until the top of the wave collapses and breaks.
