3.1 Coasts as Natural Systems

Question 1

The coast is an example of an ________ system.

Answer 1

Open

Question 2

In England and Wales, how many major sediment cells are there?

Answer 2

11.

Question 3

Define input.

Answer 3

Material or energy moving into the system from outside.

Question 4

Give an example of a coastal input.

Answer 4

Precipitation

Wind

Question 5

Define output.

Answer 5

Material or energy moving from the system to outside.

Question 6

Give an example of a coastal output.

Answer 6

Ocean currents
Rip tide
Sediment transfer
Evaporation

Question 7

Define energy.

Answer 7

Power or driving force.

Question 8

Give example f energy in the coastal system.

Answer 8

Energy associated with flowing water; the effects of gravity on cliffs and moving air (wind energy transferred to wave energy).

Question 9

Give an example of stores in the coastal system.

Answer 9

Beach, sand dunes, nearshore sediment.

Question 10

Define flow / transfer.

Answer 10

The links / relationships between the components.

Question 11

Give examples of flows / transfers in the coastal system.

Answer 11

Longshore drift, wind-blown sand, mass movement processes.

Question 12

Give an example of positive feedback in the coastal system.

Answer 12

Coastal management can inadvertently lead to an increase in erosion elsewhere along the coast.

Groynes trap sediment, depriving areas further down drift of beach replenishment, and this can exacerbate erosion.

Question 13

Give an example of negative feedback in the coastal system.

Answer 13

When the rate of weathering and mass movement exceeds the rate of cliff foot erosion, a scree slope is formed.

Over time, this apron of material extends up the cliff face; protecting the cliff face from subaerial processes.
This leads to a reduction in the effectiveness of weathering and mass movement.

Question 14

Give an example of dynamic equilibrium in the coastal system.

Answer 14

Constructive waves build up a beach, making it steeper. This encourages the formation of destructive waves that plunge rather than surge.

Redistribution of sediment offshore by destructive waves reduces the beach gradient which, in turn, encourages the waves to become more constructive.

This is a state of constant dynamic equilibrium between the type of wave and the angle of the beach.

Question 15

The primary source of energy for all natural systems is _________

Answer 15

The sun.

Question 16

How does the sun form energy?

Answer 16

Heat and light from the sun is converted by natural processes (eg photosynthesis)

Question 17

At the coast, the main form of energy is derived from the sea in the form of ________.

Answer 17

Waves.

Question 18

How are waves formed?

Answer 18

• wind
• underwater landslides creating a tsunami
• tectonic activity

Question 19

What is wind?

Answer 19

The movement of air from high pressure to low pressure.

Question 20

What affects the strength of the wind?

Answer 20

The greater the pressure gradient (pressure difference between two places), the faster and stronger the wind.

Question 21

In the U.K., the prevailing (dominant) wind comes from the _________-________.

Answer 21

South west.

Question 22

What affects wave activity?

Answer 22

• the strength of the wind; determined by the pressure gradient.
• the duration of the wind; the longer the wind blows, the more powerful the waves become.
• the fetch; the longer the fetch, the more powerful the waves.

Question 23

Define fetch.

Answer 23

The distance of open water over which the wind blows.

Question 24

How are waves formed?

Answer 24

As air moves across the water, frictional drag disturbs the surface and forms ripples of waves.

1. The water becomes shallower and the circular orbital of the water particles changes to an elliptical shape.
2. The wavelength and velocity decrease, and wave height increases - causing water to back up from behind and rise to a point where it begins to break.
3. The water rushes up the beach of swash and flows back as backwash.

Question 25

What are the two types of wave?

Answer 25

Constructive and destructive.

Question 26

Outline constructive waves.

Answer 26

• strong swash, weak backwash.
• usually associated with a gentle beach profile; although over time they build up the beach and make it steeper.
• beach gain (constructive).
• distant weather systems generate these waves in the open ocean.
• low, surging waves with a long wavelength.

Question 27

Outline destructive waves.

Answer 27

• weak swash, strong backwash.
• beach loss (destructive).
• usually associated with steeper beach profile; although over time, they flatten the beach.
• local storms responsible for these waves.
• high, plunging waves with a short wavelength.

Question 28

Outline negative feedback of constructive waves.

Answer 28

Constructive beaches are usually associated with gentle beach profiles, enabling waves to surge a long way up the beach.

However, over time as more sediment is deposited, the profile steepens. Instead, waves become more destructive (plunging rather than surging); removing material from the beach and depositing it offshore.

This results in the beach becoming less steep - encouraging constructive rather than destructive waves to form. This toing and froing results in a state of dynamic equilibrium.

Question 29

What are tides?

Answer 29

Changes in the water level of seas and oceans caused by the gravitational pull of the moon and sun.

Question 30

The UK experiences ______ high and low tides each day.

Answer 30

Two.

Question 31

Define tidal range.

Answer 31

The relative distance in height between high and low tides each day.

Question 32

The tidal range is affected by…

Answer 32

The relative position of the sun and the moon - highest during spring tides and lowest during neap tides.

Question 33

A high tidal range creates high…

Answer 33

Tidal currents

Question 34

Where are tidal currents particularly strong?

Answer 34

In estuaries and narrow channels.

Question 35

What are rip currents?

Answer 35

Strong, localised underwater currents that occur on some beaches - posing considerable danger to swimmers and surfers.

Question 36

How do rip currents form?

Answer 36

A series of plunging waves cause a temporary build up of water at the top of the beach.
Met with resistance from the breaking waves, the backwash is forced below the surface, following troughs and undulations.

Question 37

Rocky coasts tend to be found in _______ ___________ environments.

Answer 37

High energy.

Question 38

Where are rocky coasts (in high energy environments) generally found in the U.K.?

Answer 38

• where rates of erosion exceed rates of deposition.

- stretches of the Atlantic facing coast, where waves are powerful for much of the year (eg Cornwall).

Question 39

Give an example of an erosional landform.

Answer 39

Headland, cliff, wave cut platform

Question 40

Where are erosional landforms usually found?

Answer 40

Rocky coasts, in high energy environments.

Question 41

Sandy (and estuarine) coasts are generally indicative of ______ _________ ________________.

Answer 41

Low energy environments.

Question 42

In the U.K., where are sandy beaches (in low energy environments generally found)?

Answer 42

• where the rate of deposition exceeds the rate of erosion.

- stretches of coast where the waves are less powerful. Or where the coast is sheltered from large waves.

Question 43

Name a landform that forms at sandy coasts (in low energy environments).

Answer 43

Beaches, spits, coastal plain.

Question 44

Define wave refraction.

Answer 44

The distortion of wave fronts as thy approach an indented shoreline.

This causes energy to be concentrated at headlands and dissipated at bays. Also accounts for th presence of erosive features at headlands (cliffs, stacks) and disposition features in bays (beaches).

Question 45

Outline an example of negative feedback re wave refraction.

Answer 45

Variations in rock strength lead to the formation of headlands and bays. This causes wave refraction, which, in turn encourages erosion of the headlands and deposition in the bays - working against the erosion of the softer rock that formed the bay originally.

If conditions remained stable for a long period of time, a state of equilibrium would be reached, where the shape of the coastline remains static due to a balance between the potential erodability of the rocks and effect of wave refraction.