Wave Generation + Characteristics

Question 1

What is the crest of a wave?

Answer 1

Highest point

Question 2

What is the trough of a wave?

Answer 2

Lowest point

Question 3

What is the wave length?

Answer 3

Distance from crest to crest

Question 4

What is the wave height?

Answer 4

Vertical distance between crest + trough

Question 5

How do waves form?

Answer 5

• 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

Question 6

What influences the size of+ energy of waves?

Answer 6

• strength of wind
• duration of wind
• size of the fetch

Question 7

How does the strength of the wind influence the size + energy of a wave?

Answer 7

• 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

Question 8

How does the duration of the wind influence size + energy of waves?

Answer 8

• if the wind is active for longer periods of time, the energy of the waves will build up + increase

Question 9

How does the size of the fetch influence the size + energy of waves

Answer 9

• fetch is the distance over which the wind blows
• the larger it is, the more powerful the waves will be

Question 10

How are shallow water waves formed?

Answer 10

• 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

Question 11

What is spilling?

Answer 11

• steep waves
• gentle beach gradient
• gradual peaking
• becomes unstable + spills forward
• strong Swash

Question 12

What is plunging?

Answer 12

• steeper beaches
• wave face becomes vertical + plunges
• strong backwash

Question 13

what is surging?

Answer 13

• low steepness of waves
• steep beach gradient
• waves don’t break but surge gently up beach

Question 14

What is Swash + backwash?

Answer 14

• 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

Question 15

What are constructive waves?

Answer 15

• tend to deposit material, creating deposition land forms + increase size of beaches
• Swash is stronger than backwash

Question 16

Characteristics of a constructive wave?

Answer 16

• 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

Question 17

What is a destructive wave?

Answer 17

• removes depositional landforms through erosion, thereby decreasing the size of the beach
• backwash is stronger than the Swash

Question 18

Characteristics of a destructive wave?

Answer 18

• 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

Question 19

What are high energy coastlines?

Answer 19

• 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

Question 20

What are low energy coastlines?

Answer 20

• 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

Question 21

What is wave refraction?

Answer 21

• 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 bats leading to the formation of features associated with low energy environments such as beaches

Question 22

Why do waves break?

Answer 22

• 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