Coasts as natural systems

Question 1

What are the three sources of energy?

Answer 1

1. Waves and wind
2. Tides
3. Currents

Question 2

What is the definition of waves?

Answer 2

They are generated by the wind blowing over the sea.

They are affected by:

1. Wind speed- pressure gradient
2. Duration of the wind
3. Fetch- distance the wave has travelled

Question 3

What are the two types of waves?

Answer 3

1. Constructive= strong swash so build up the beach

2. Destructive= strong backwash so cause beach loss

Question 4

What are the characteristics of constructive waves?

Answer 4

• Form in the open ocean.
• Long wavelength
• Strong swash and weak backwash.
• Gentle profile so build up the beach.

Question 5

What are the characteristics of destructive waves?

Answer 5

• Caused by local storms.
• Short wavelength
• Weak swash and strong backwash.
• Steeper profile, so over the time they will flatten the beach.

Question 6

What is the definition of tides?

Answer 6

Changes in water levels of seas and oceans caused by gravitational pull of the moon and sun.
There are 2 high tides and 2 low tides per day and 2 spring tides a month and 2 neap tides. .

Question 7

What is the definition of currents?

Answer 7

They are permanent or seasonal movement of water in the ocean.

Question 8

What are currents generated by?

Answer 8

1. Tides
2. Wind
3. Heat and salinity
4. Earths rotation

Question 9

What is the definition of longshore current?

Answer 9

Water that runs parallel to the coast caused when the waves hit the coast at an angle. This leads to LSD.

Question 10

What is the definition of rip currents?

Answer 10

Water which moves away from the coast, caused when the waves lead water to ‘pile up against the cost on incoming tide.
Usually occurs when there is a change in direction of coast line.

Question 11

What is the definition of global currents?

Answer 11

Have an impact on the planets oceans and weather systems.

E.G. The North Atlantic Drift

Question 12

What is the different between high and low energy coasts?

Answer 12

• High energy coasts have powerful waves and the rate of erosion rates exceeds deposition rates.
• Low energy coasts have less powerful waves so deposition rates exceed erosion.

Question 13

What is wave refraction?

Answer 13

Wave refraction is the bending of a wave as it propagates over different depths.
This causes energy to be concentrated at headlands and dissipated in bays.
Causes erosion at headlands.

Question 14

What are inputs, outputs, stores and flows of coastal systems?

Answer 14

Inputs:

• Waves and wind
• Tides and currents
• Solar energy
• Sediment

Flows/transfers:

• Links in the system
• Driven by energy inputs such as waves and wind

Stores/components:
- Headlands and bays 
- Cliffs
- Wave cut notches
- Beaches, spits etc
(Anything physical around the coast)

Outputs:

• Dissipation of wave energy
• Sediment sinks
• Sediment which accumulates above high water mark

Question 15

What is the difference between spring tides and neap tides?

Answer 15

Spring tide has a large tidal range and occurs when the moon and the sun are aligned.

Neap tide has a small tidal range as there is not much difference between high tide and low tide. This occurs when the sun and the moon are at right angles.

Question 16

What are the three processes that change inputs?

Answer 16

When inputs are transferred to components they form coastal landforms, this can be done by:

1. Marine erosion
2. Sub-aerial erosion
3. Deposition

Question 17

Types of erosion:

Answer 17

Erosion is the wearing away of a coastal landscape by the sea.

Abrasion-
- Waves pick up pebbles and when they break these hurl at the cliff.

Hydraulic action-
- Sheer force of powerful waves breaks the cliff as it crashes.

Attrition-
- Rocks carried by water smash into each other and break into small pieces.

Solution-
- Acid in water can dissolve alkaline rocks.

Question 18

Types of weathering:

Answer 18

Sub-aerial process which gradually breaks down the landscape.

Salt-weathering-
- Salt water evaporates salt crystals grow which creates stresses in rock.

Carbonation-
- Water absorbs co2 forms calcium carbonate which dissolves rocks.

Biological weathering-
- Break down of rocks by organic activity.

Freeze-thaw-
- Water enters gaps then freezes and expands then thaws leaving larger gap. Process continues.

Question 19

Types of mass movement:

Answer 19

Mass-movement is a sub-ariel process which is he downhill movement of rock and soil.

Land slides/ rock falls-
- Large rocks fall rapidly down cliff face.

Mudflows-
- Wet soil flows like a liquid down the slope towards the sea.

Rotational slip-
- Slice of the cliff slides intact towards the sea. (Sheringham)

Soil creep-
- Individual rocks or soil moves very slowly down shallow slope.

Question 20

Holbeck Hall, Scarborough (mass movement):

Answer 20

• Rotational slumping involving 1 million tonnes of glacial till cut back the 60m high cliff by 70m.
• Caused by heavy rainfall, 140mm in 2 months and a coastline made of permeable glacial till on top of impermeable gritstone.
  Till became quickly saturated and it slid forward across the top of the impermeable gritstone.

Programme of emergency coast protection and cliff stabilisation undertaken to prevent further mass movement done by (£2M):

• Rock armour revetment in front of landslide, 30,000 tonnes of rock.
• Failed slope re-profiled to 24 degrees and compacted to reduce infiltration. Vegetation added to stabilise.
• Slope drainage put in place to drain the cliff.