Waves

Question 1

What are waves important for?

Answer 1

They are a method of moving energy, which ultimately erodes and shapes coastlines.

Question 2

How are waves generated?

Answer 2

1. Wind speed is slower at the surface of water due to friction between air and water.
2. Friction produces turbulence in air at the waters surface, also transferring energy into the water.

Question 3

How does WIND effect waves?

Answer 3

Faster wind -> more kinetic energy -> larger waves

Question 4

How does TIME effect waves?

Answer 4

Long wind blow -> more time for energy transfer -> stronger waves

Question 5

How does the FETCH effect waves?

Answer 5

Longer fetch -> more opportunity to transfer energy to water -> stronger waves

Question 6

Crest…

Answer 6

Highest point of a wave

Question 7

Trough…

Answer 7

Lowest point of a wave

Question 8

Amplitude…

Answer 8

Height from stationary water to crest

Question 9

Wave height…

Answer 9

Height from trough to crest

Question 10

Wavelength…

Answer 10

Horizontal distance between trough and trough/crest and crest

Question 11

Time period…

Answer 11

Time take for wave to travel one wavelength (s)

Question 12

Frequency…

Answer 12

Number of crests/troughs passing one point per second

Question 13

Velocity…

Answer 13

Speed the wave travels

Wave speed

Question 14

What is the ratio of height:wavelength that waves become unstable and break?

Answer 14

7:1

Question 15

What happens as waves approach the coast?

Answer 15

Water gets shallower, waves get bigger, energy being carried reaches the land.

Question 16

What happens in the process of SHOALING?

Answer 16

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.

Question 17

Features of a Constructive Wave

Answer 17

• Long period
• Long wavelength
• Low amplitude (relatively calm)
• Strong swash
• Weak backwash

Question 18

Role of a Constructive wave

Answer 18

Deposit more material than they remove therefore build up gentle beaches.
Development of berms due to repeated action of pushing material up a beach.

Question 19

Features of a Destructive Wave

Answer 19

• Short period
• Short wavelength
• High amplitude
• Steep profile (particularly during storms)
• Weak swash
• Strong backwash

Question 20

Role of a Destructive Wave

Answer 20

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)

Question 21

When does Wave Refraction take place?

Answer 21

As a wave approaches an irregular coastline.

Question 22

Why are waves slowed during Wave Refraction?

Answer 22

As waves approach a coastline, waves are slowed by friction as the water shallows approaching the headland.

Question 23

Which areas of the wave move faster and why?

Answer 23

The part of the wave in deeper water approaching the bay moves faster as it is not slowed by friction.

Question 24

What occurs around the headland?

Answer 24

Waves refract around the headland and the orthogonal converge.

Question 25

What occurs around the bays?

Answer 25

Orthogonal diverge and energy is dissipated leading to deposition.

Question 26

What occurs as a result of Wave refraction?

Answer 26

• 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.