1

QU: Game of Thrones ‐ a tale of coastal succession. AIM: To explain how vegetation can stabilise sandy and estuarine coastlines.

Killed by a boarPoisoned

Jumped(suicide)

RobertGeoffery 

Tommen

Cersei

Current Monarch

Heir Apparrent?Heir Apparrent?

ST: Succession to the Iron throne. Who replaced who and how did the succession come about?

2

• Often stores and traps sediment in place

• Often exposes kilometres of beach across the foreshore at low tide.

• Can change rapidly. Very dynamic.

• Often have additional sediment input from rivers.• The backshore often contains dune systems

• Waves are constructive and deposit sediment

• The coastline is indistinct as there is a gradual transition from sea to land. Low profile.

• Develops well in macrotidal areas where sediment is exposed at low tide and can dry and be blown to the backshore.

• Saltmarsh often develops and covers the near shore and backshore areas.

Remember these characteristics from your homework? Can you spot them in the image above?

3

Key to stabilising estuarine and sandy coastlines is vegetation. Look at the images below. How does the vegetation help? Discuss.

Dunes

Saltmarsh

Spec Speak

4

Critical factors for sand dune creation:

• Source of abundant sand

• Vegetation • Large tidal range

to foster sand accumulation traps and and stabilizes sand

• Relatively consistent on shore wind

 to expose more sand at low tide that can dry out and be moved by onshore breezes.

to push sand into the dunes

to provide material for them to grow

Task: These are the 4 factors needed for sand dune creation ‐ for each one, explain WHY it is necessary

 

5

Dunes form when sand is blown from the beach and becomes stabilised by the growth of vegetation, notably marram grass. The scale and character of the dune system depends on the interaction between physical factors, such as wind and wave regime and the sand supply, and biotic controls, such as plant succession and grazing pressure. Unconsolidated sand is by its nature a highly unstable substrate and the survival of dunes depends on the ability of plants to maintain at least a partial cover on the dunes.

Therefore dunes can reduce coastal recession rates!!

• There are three ways wind can move sand:• Suspension• Moves the finest grains • 1%• Impact creep• Moves the heaviest grains• 4% • Saltation• Moves intermediate grains• 95%

http://www.youtube.com/watch?v=yRRl3HyR3mc

 

6

On your copy of an idealised sand dune system. (psammosere)..

Fill in the rows of figures. Allocate them to the correct variable.

0-20 20-80 80-150 150-300 300-500 500-700 variable 700-2500 2500+

- 0-50 50-100 100-125 125-150 150-250 varies 250-400 >400

8.5 8.0 7.5 7.0 6.5 6.0 4.5

10 8 8 5 1 <0.1

<1 2.5 5 10 20 >40

The changing variables above lead to plant succession. This is where the number of plants and species increase in diversity and complexity with distance from the sea. One species dies out and another takes over eg. marram grass on the embryo dunes gives out to gorse and trees in the grey dunes. Hence the Game of Thrones analogy. remember that increasing vegetation stabalises dunes, 'fixing it in place'

 

TASK: 1­Explain how the changes in Humus levels come about and how this allows succession to happen.  Remember many plants do not like overly alkali soils.2 ­ Explain how this process stabilises the coast.3 ­ What is meant by the terms mobile and fixed dunes? Why is this the case?

7

8

Vegetation also colononises saltmarshes through succession. Saltmarshes occur in low energy areas of the coast with macro­tidal ranges and a plentiful sediment supply.

9

As tidal waters flood the saltmarsh sediments gets trapped in the vegetation. This builds the marsh upwards so in time it is no longer covered by seawater. eventually more vegetation replaces or succeeds the existing plants just as with a dune system.

TASK: On your copy of the map (next slide) allocate the descriptions to the correct letter.

10

A B C D

F

E

D

C

B

A

E

F

Algal stageExposed tidal mud

Pioneer stage. Sand and mud covered each tide.A few salt tolerant plants.

Establishment stage

Many more alt tolerant Plants have started to colonise sand and

mud. Creeks drain the

marsh.

Stabilisation stageMarsh is more developed and

plant life is more varied and dense increasing the

height of the marshthrough years of decay and soil development.

Climax vegetationNo longer considered saltmarsh.

Stands above

highest tide levels. Now colonised by

trees.

Former cliff line. Now forested.

Ext: Why does soil deepen on the saltmarsh with distance from the sea?

11

Salt Marsh developmentAnnotate this copy correctly using those on the board.

Pg. 98 AQA AS will help.

Ext: Why does soil deepen on the saltmarsh with distance from the sea?

A B C D

F

E

D

C

B

A

12

(Halosere)

Succession

plantsreplacesaltmarshdunesgame of throneskings or queensstages

Embryo dune

Sandstartfirstbeachbackshoregreyyellow

Taboo

Stabalisation

dunes vegetationsaltmarshslowrecessionfixedmobile

13

resource slides past this point

14

15