Wave Generation + Characteristics Flashcards
(15 cards)
1
Q
What are the characteristics of waves?
A
- crest (highest point of wave)
- trough (lowest point of wave)
- wavelength (distance from crest to crest)
- wave height (vertical distance between crest + trough)
2
Q
How are waves formed?
A
- winds move across surface of water, causing frictional drag which creates small ripples + waves
- this leads to circular orbital motion of water particles in ocean
- as seabed becomes shallower towards coastline, orbital of water particles become more elliptical, causing more horizontal movement of waves
- wave height inc, but wavelength + wave velocity both dec
- this causes water to back up from behind wave until wave breaks + surges up beach
3
Q
What 3 factors influence the size + energy of a wave?
A
- strength of wind
- duration of wind
- size of fetch
4
Q
How does the strength of the wind influence the size + energy of a wave?
A
- wind = movement of air from high to low pressure
- diff pressure areas are caused by variations in surface heating by sun
- larger diff in pressure between 2 areas = stronger winds = stronger waves
5
Q
How does the duration of the wind influence the size + energy of a wave?
A
- if wind is active for longer periods of time, energy of waves will build up + inc
6
Q
How does the size of the fetch influence the size + energy of a wave?
A
- fetch = distance over which wind blows
- larger it is, more powerful waves will be
7
Q
What is swash + backwash?
A
- how water moves onto + off a beach
- swash = movement of wave onto beach after a wave breaks. Material being carried by waves is deposited onto beach
- movement of wave back down beach, which drags any material off a beach
8
Q
What are constructive waves?
A
- tend to deposit material, creating depositional landforms + inc size of beaches
- swash is stronger than backwash
9
Q
What are the characteristics of a constructive wave?
A
- formed by weather systems that operate in open water
- long wavelength, bc have an elliptical orbit bc of friction
- flat, low waves that gently spill over
- strong swash, which pushes material up beach, + weak backwash, bc water percolates into sand
- occurs on gently sloped beaches
- low frequency of 6-8 waves per min
10
Q
What are destructive waves?
A
- remove depositional landforms through erosion, so dec size of beach
- backwash is stronger than swash
11
Q
What are the characteristics of a destructive wave?
A
- formed by localised storm events w strong winds
- short wavelength
- steep, high waves that plunge forward
- weak swash + strong backwash, bc of little percolation so beach cliffs can form
- occurs on steeply sloped beaches
- high frequency of 10-14 waves per min
12
Q
What are high energy coastlines?
A
- associated w more powerful waves, so occur in areas w a large fetch
- typically have rocky headlands + landforms, + fairly frequent destructive waves
- so these coastlines are often eroding bc rate of erosion is > rate of deposition
13
Q
What are low energy coastlines?
A
- have less powerful waves + occur in sheltered areas
- have constructive waves, so form sandy beaches
- form depositional landforms bc rate of deposition is > rate of erosion
14
Q
What is wave refraction?
A
- when waves turn + lose energy around a headland on uneven coastlines
- wave energy is focused on headlands, creating erosive features in these areas
- energy is dissipated in bays, causing features associates w lower energy envi.s, such as beaches, to form
15
Q
Why do waves break?
A
- when waves move into shallow waters near shore, they interact w sea floor
- this causes friction between wave + floor, + so wave slows down
- this causes wavelength to dec, causing wave to become steeper (shoaling)
- shoaling process continues until wave height can no longer bc supported bc it’s too high, + so wave breaks
