Wave Generation + Characteristics Flashcards
1
Q
What is the crest of a wave?
A
Highest point
2
Q
What is the trough of a wave?
A
Lowest point
3
Q
What is the wave length?
A
Distance from crest to crest
4
Q
What is the wave height?
A
Vertical distance between crest + trough
5
Q
How do waves form?
A
- winds move across the surface of the water = frictional drag, which creates small ripples + waves
- this leads to a circular orbital motion of water particles in the ocean
- as the seabed becomes shallower towards the coastline, the orbit of the water particles becomes more elliptical = causes more horizontal movement of waves
- the wave height increases, but wave length + velocity both decrease
- this causes water to back up from behind the wave until the wave breaks + surges up the beach
6
Q
What influences the size of + energy of waves?
A
- strength of wind
- duration of wind
- size of the fetch
7
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
- the different pressure areas are caused by variations in surface heating by the sun
- larger the difference in pressure between two areas = strong winds = stronger waves
8
Q
How does the duration of the wind influence size + energy of waves?
A
- if the wind is active for longer periods of time, the energy of the waves will build up + increase
9
Q
How does the size of the fetch influence the size + energy of waves
A
- fetch is the distance over which the wind blows
- the larger it is, the more powerful the waves will be
10
Q
How are shallow water waves formed?
A
- waves approach the shore + the wave length is greater than depth
- the wave touches the bottom + experiences friction
- the wave starts to have an eleipitcal orbit + becomes a ‘wave of translation’
- wave length starts to decrease + wave height increases
- this is called shoaling + beaches begin to form
11
Q
What is spilling?
A
- steep waves
- gentle beach gradient
- becomes unstable + spills forward
- strong Swash
12
Q
What is plunging?
A
- steeper beaches
- wave face becomes vertical + plunges
- strong backwash
13
Q
what is surging?
A
- low steepness of waves
- steep beach gradient
- waves don’t break but surge gently up beach
14
Q
What is Swash + backwash?
A
- how waves move onto + off a beach
- Swash = movement of the wave onto the beach after a wave breaks. Material being carried by waves is deposited onto the beach
- backwash = movement of the wave back down the beach. Backwash drags any material off a beach
15
Q
What are constructive waves?
A
- tend to deposit material, creating deposition land forms + increase size of beaches
- Swash is stronger than backwash
16
Q
Characteristics of a constructive wave?
A
- formed by weather systems that operate in the open water
- elliptical orbit due to friction = long wave length
- flat waves which spill over
- strong Swash pushes material up the beach + weak backlash because water percolates into sand
- occurs on gently sloped beaches
17
Q
What is a destructive wave?
A
- removes depositional landforms through erosion, thereby decreasing the size of the beach
- backwash is stronger than the Swash
18
Q
Characteristics of a destructive wave?
A
- formed by localised storm events with strong winds
- short wavelength
- steep waves which plunge forward
- weak Swash + strong backwash + little percolation meaning beach cliffs can form
- occurs on steeply sloped beaches
19
Q
What are high energy coastlines?
A
- associated with powerful waves so occur in areas where there is a large fetch
- typically have rocky headlands + landforms
- fairly frequent destructive waves
- as a result these coastlines are often eroding as the the rate of erosion exceeds the rate of deposition
20
Q
What are low energy coastlines?
A
- less powerful waves + occur in sheltered areas
- constructive waves prevail = sandy beaches
- there are landforms of deposition as the rate of deposition exceeds the rate of erosion
21
Q
What is wave refraction?
A
- process by which waves turn + lose energy around a headland on uneven coastlines
- the wave energy is focused on the headlands, creating erosive features in these areas
- the energy is dissipated in bays leading to the formation of features associated with low energy environments such as beaches
22
Q
Why do waves break?
A
- waves interact with the sea floor when they move into shallower water near the shore = friction between the wave + flow = wave slows down
- wavelength decreases when the wave slows down, causing the wave to become steeper = shoaling
- the shoaling process continues until the wave heigh can no longer be supported as it is too high = wave breaks
