3.1.3.2 Systems and Processes

Question 1

Sources of coastal energy

Answer 1

Coastal energy is the power and driving force behind the transfers and flows in the coastal system. It includes:

• Wind
• Tides
• Waves
• Currents

Question 2

What is wind?

Answer 2

Winds are created by air moving from areas of high pressure to areas of low pressure.

During events such as storms, the pressure gradient is high and winds can be very strong.

Strong winds can create powerful waves.

In some areas there is a prevailing wind which causes higher energy waves than winds that change direction constantly.

Question 3

What are waves?

Answer 3

Waves are created by the wind blowing over the surface.

The friction between the wind and the sea gives the water a circular motion.

The affect that the waves have on the shore depends on its height which is affected by wind speed and the fetch of the wave.

A high wind speed and a long fetch create higher and more powerful wave.

As waves approach the shore they break.

Friction between the wave and the sea bed slows the bottom of the waves and makes their motion more elliptical.

Question 4

What is fetch?

Answer 4

The fetch of the wave is the maximum distance of the sea the wind has blown over it creating waves.

Question 5

What is swash?

Answer 5

Water rushing up the beach.

Question 6

What is backwash?

Answer 6

Water washing back towards the sea.

Question 7

Constructive Waves

Answer 7

Waves with a low frequency (6-8 waves per minute).

They are low and long with and elliptical side profile.

The powerful swash carries material up the beach and deposits it.

Question 8

Destructive Waves

Answer 8

Waves with a high frequency (10-14 waves per minute).

They are high and steep with a more circular side profile.

The strong backwash removes sediment from the beach.

Question 9

What are tides?

Answer 9

Tides are a periodic rise and fall of the oceans surface caused by the gravitational pull of the moon and sun.

Tides affect the position at which the waves break on the beach.

The area between min and max tide is where most landforms are created and destroyed.

Question 10

What are currents?

Answer 10

A current is the general flow of water in one direction.

It can be caused by wind, variations in temperature and salinity and transport sediment along the coast.

Question 11

Low Energy coasts

Answer 11

Low energy coasts receive low inputs of energy in the form of low gentle waves.

These can be caused by gentle winds, short fetches and gently sloping of shore zones.

Low energy coastlines often have saltmarshes and tidal mudflats.

The rate of deposition is often higher than the rate of erosion.

Question 12

Sediment Sources

Answer 12

• Rivers (majority of sediment)
• Cliff erosion
• Wind
• Glaciers
• Offshore
• Longshore drift

Question 13

Sediment Budget

Answer 13

The sediment budget is the difference between the amount of sediment that enters the system and the amount that leaves.

If more sediment enters it is a positive budget meaning the coastline builds outwards and vice versa.

Question 14

The Littoral Zone

Answer 14

The littoral zone is the area of land between the cliff’s or dunes on the coast and the offshore area that is beyond the influence of the waves . The littoral zone is constantly changing because of:

• Short-term factors like tides and storm surges
• Long-term factors like changes in sea level and human intervention

Question 15

Why do waves vary?

Answer 15

The type of waves in a coastal environment may vary:

• In summer, constructive waves dominate but destructive waves dominate in winter
• Constructive waves may become destructive waves if a storm begins
• Climate change may increase the storm frequency within the UK
• Coastal management may affect the type of waves that occur

Question 16

Wave Refraction

Answer 16

Wave refraction is the process by which waves turn and lose energy around a headland on uneven coastlines. The wave energy is focussed on the headlands , creating erosive features in these areas. The energy is dissipated in bays leading to the formation of features associated with lower energy environments such as beaches

Question 17

Weathering and its types

Answer 17

Weathering is the breakdown of rocks over time, leading to the transfer of material into the littoral zone, where it becomes an input to sediment cells. The types of weathering are:

• Mechanical (physical) weathering
• Chemical weathering
• Biological weathering

Question 18

Mechanical (Physical) Weathering

Answer 18

• Freeze-thaw (Frost-Shattering): Water enters cracks in rocks and then the water freezes and expands in volume causing cracks to develop
• Salt Crystallisation: As seawater evaporates, salt is left behind. Salt crystals will grow
  over time, forces the cracks to widen. Salt can also corrode ferrous rock
• Wetting and Drying: Rocks such as clay expand when wet and then contract again when they are drying and these cycles cause the rocks to break up

Question 19

Chemical Weathering

Answer 19

• Carbonation: Rainwater absorbs CO2 from the air to create a weak carbonic acid Acid rain reacts with limestone to form calcium bicarbonate, which is then easily dissolved allowing erosion
• Oxidation: When minerals become exposed to the air it will become oxidised which will increase its volume causing the rock to crack. Most common with iron minerals
• Solution: When rock minerals such as rock salt are dissolved

Question 20

Biological Weathering

Answer 20

• Plant Roots - Roots of plants growing into the cracks of rocks, which exerts pressure, eventually splitting the rocks
• Birds - Some birds such as Puffins dig burrows into cliffs weakening them
• Rock Boring - Many species of clams secrete chemicals that dissolve rocks
• Seaweed Acids - Kelp contains sulphuric acid, which dissolves rock minerals
• Decaying Vegetation - Water flows through decaying plants and becomes acidic

Question 21

Erosion (six)

Answer 21

• Abrasion (rocks and sediment smash against the cliff)
• Hydraulic action (air in cracks is compressed causing pieces of cliff to break off)
• Cavitation (as waves recede the compressed air expands causing pieces of the cliff to break off)
• Wave quarrying (the energy of the wave it enough to break part of the cliff)
• Solution (soluble rocks get gradually dissolved by the saltwater)
• Attrition (bits of rock in the water smash against each other)

Question 22

Transportation

Answer 22

The four main processes of transportation are:

• Traction – Large, heavy sediment rolls along the sea bed, pushed by
  currents
• Saltation – Smaller sediment bounces along the sea bed
• Saltation – Smaller sediment bounces along the sea bed
• Solution – Dissolved material is carried within the water

Question 23

Deposition

Answer 23

Deposition occurs when sediment becomes too heavy for the water to carry, or if the wave loses energy.

Question 24

Longshore Drift

Answer 24

• Waves hit the beach at an angle determined by the direction of the prevailing wind
• The waves push sediment in this direction and up the beach in the swash
• The wave then carries sediment back down the beach in the backwash
• This moves sediment along the beach over time