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Revision 1Revision 1

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This is what we need to talk This is what we need to talk aboutabout

What are the 3 processes that change the shape of the land? What do each of the 3 words mean? [Think of the little man!]What are 4 ways water eroded rock?What are the 4 ways water moves the rock?What do these words all mean? Attrition, Abrasion, Hydraulic action, Corrosion, Traction, Saltation, Suspension, Solution

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There are 3 processes at work There are 3 processes at work

Erosion Transport Deposition

I am using my hammer

to wear away this

rock

I am carrying away the

pieces

I cannot carry them any further so I drop

them

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Water erosion by wavesWater erosion by waves

.

What can you

see here?

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This shows that the sand has This shows that the sand has been transported and depositedbeen transported and deposited

What can you see and why is it like that?

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Deposition is a bit easier!Deposition is a bit easier!

Is what happens when the water runs out of energy and drops whatever it is carrying

Kiama Downs Beach, just north of Sydney

Where is that?See those rocks in the foreground?They are being

eroded away and will end up on the beach.

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So there are 3 processes at work So there are 3 processes at work

Erosion Transport Deposition

I am using my hammer

to wear away this

rock

I am carrying away the

pieces

I cannot carry them any further so I drop

them

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Erosion 1Erosion 1Attrition is the collision of rock fragments in the water against one another. The waves carrying rocks that knock against each other and pieces get broken off, making them smoother and rounder

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Erosion 2Erosion 2

Abrasion occurs when rocks and stones carried by the waves wear away the base of the cliffs

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Erosion 3Erosion 3

Hydraulic action. When waves fall against the cliffs, air is forced into the cracks and is squashed.As the wave withdraws, the air expands causing little explosions and so the cracks become enlarged

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Erosion 4Erosion 4

Corrosion is the process by which water reacts chemically with soluble minerals in the rocks and dissolves them. 

If you would like to watch the animation

from which the diagrams for erosion came from, there is ias link on the wiki page to the BBC

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Transportation 1Transportation 1

A waves carry or transport eroded materials such as mud, sand, boulders and dissolved materials. Sometimes this is towards the land or sometimes is it away from the land but often it is along the coast to somewhere elseThese materials are known as its load.its load. The load is carried along by four processes.

traction traction saltation saltation suspension suspension solutionsolution

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Transportation 2Transportation 2

Traction is where boulders or stones are rolled along the ocean-bed by the force of the water

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Transportation 3Transportation 3

Saltation is when small pebbles bounce along and leapfrog over each other.

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Transportation 4Transportation 4

Suspension very fine particles such as clay, silt and fine sand are carried along in the river. They are held up by the water as they float because they are very, very small!

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Transportation 5Transportation 5

Transportation in solution is when dissolved materials resulting from corrosion (when the eroded material is dissolved out of the rocks) and are invisible to the naked eye.

You cannot see anything

because they are too small!

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DepositionDeposition

A waves drop their loadtheir load when the speed or volume of the waves decrease. The load, which it carries, is deposited. The heavier material is deposited first and the finer material carried further.

Deposition is likely to occur when:waves enter an area of shallow waterwaves enter a sheltered areathere is little wind

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Match the word to the definitionMatch the word to the definition

Attrition

Abrasion

Hydraulic

action

Corrosion

Traction

Saltation

Suspension

Solution

The water dissolving away the cliffsThe force of the water wearing away the cliffsTiny particles of clay or sand being carried away by floating in the wavesRocks hitting each other, breaking pieces off, making them smaller and smootherRocks wearing away the coast lineLanger boulders being dragged along the floor of the oceanDissolved chemical being taken away by the waveSmaller pebbles leapfrogging over each other as they move

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Can you sort the Can you sort the words we have words we have

learnt into learnt into erosion and erosion and deposition?deposition?

Try here!!Try here!!

http://classtools.net/my/dhttp://classtools.net/my/dustbin35961TESTER.htmustbin35961TESTER.htm

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Changes in the Changes in the shape of the shape of the

coastcoast

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Next set of questionsNext set of questions

How is a wave cut platform made?Can you label a cave, an arch, a stack and a stump?Could you put them in the right order and explain how one comes from the other?Do you know how long shore drift works?Do you know the difference between a tombolo and a sand spit?

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ErosionErosion

How easily a coast is eroded depends on how hard the rock is

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How cliffs are erodedHow cliffs are eroded

The tougher rocks of the headlands are gradually eroded away by all the methods of erosion and gradually a small ‘Wave-cut Wave-cut notchnotch’ is made. As it gets bigger, the overhanging rock will eventually tumble into the sea.

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How cliffs are erodedHow cliffs are eroded

Over time the cliff retreats leaving a wave-cut wave-cut platformplatform just below the surface, that show when the tide is outThis is in Dorset near Purbeck at Kimmeridge Bay.

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There are some special coastal There are some special coastal featuresfeatures

These form where chalk or limestone form the hard band of rock.Here the erosion is help by solution or corrosion. If the water is slightly acid, then the calcium carbonate that makes up these rocks will dissolve slowly.The rocks were laid down millions of years ago in a warm sea and are made mostly of the shells of molluscs.

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cliffcliff

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crackcrack

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cavecave

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archarch

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stackstack

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stumpstump

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Some examplesSome examplesOld Harry’s RockOld Harry’s Rock

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Direction of swash

Bac

kwas

h

Longshore Drift

Long shore driftLong shore drift

The waves are blown in at an angle and ‘swash’ the pebbles up the beachThe water ‘backwashes’ down the quickest way taking the pebbles with it – So the sand and pebbles are moved from left to right

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Direction of swash

Bac

kwas

h

Longshore Drift

Long shore driftLong shore drift

The wooden partitions are called groynes. What are they doing?Why have they been put there?But if the groynes were not there ……

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And this happens if the long shore And this happens if the long shore drift is allowed to carry ondrift is allowed to carry on

The coast changes direction

But the long shore drift carries on

But the load gets dropped as the longshore drift

looses power

Deposits and seed are caught behind the shingle

bar and a salt marsh begins to grow

What is this feature

called? It begins with

S

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What can happen with longshore What can happen with longshore drift?drift?

The sand and shingle are dragged down the coast from the NW.The blue line shows a shingle bankIt continued across the gap between the main land and the island to form a tombolo. tombolo.

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But in some But in some places our coast places our coast is disappearing!is disappearing!

What can we do?What can we do?http://www.andrewdunnphoto.com

/

Erodedcliffpacifica.jpg

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Do you know the difference between hard and soft engineering? Do you know the advantages and disadvantages of each? Could you decide from a picture whether it was hard or soft engineering?

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Coastal ManagementRapid coastal erosion often poses a threat to the settlement, industry and recreation that has grown up along the coast and we often look to protect the coast from erosion through appropriate management of the coastal system.There are a number of possible approached to coastal management:

1. Building Structures to defend the Coast2. Pre-planning3. Do-Nothing

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Building structuresBuilding structures

Can be divided into 2 typesHard EngineeringThese solutions generally involve concrete, metal, stone and other hard wearing materials that are intended to stop erosion and take little account of the environment.Soft EngineeringThese methods try not to disrupt the environment and tend to be used where the environment is more important than say a town or road

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Hard Engineering Hard Engineering solutionssolutions

vertical sea walls (formed of concrete, rock, sheet piling or timber) revetments (sloping ramps of concrete or rock) flood embankments (formed of metal, concrete, rock, timber, rubble or turf) rock armouring rip-rap is a general term covering less tightly specified dumped or placed rock structures)

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Hard Engineering solutionsHard Engineering solutions

gabions (wire baskets filled with stone, stacked vertically or stepped; often sloped to form gabion mattresses) groynes (fences or walls generally perpendicular to the coastline, designed to intercept sand and gravel movement along the beach; constructed from timber, sheet piling, concrete or boulders; modern designs are often Y-, T- or L-shaped).

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Would you have these?Would you have these?

AdvantagesAdvantagesThey all manage to absorb the energy from the waves and so reduce erosionThey are long lasting

DisadvantagesDisadvantagesThey are not environment friendlyThey are not prettyThey are expensive

What if anything

could make a home here?

http://en.wikipedia.org/wiki/File:11-8-07_riprap_photo.jpg

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Soft Engineering solutionsSoft Engineering solutions1. beach renourishment - addition of sand or gravel to a beach to restore former levels2.fencing - to reduce wave scour and promote sand deposition and to trap and accumulate wind blown sand3. dune grass planting - stabilisation of bare sand dune surfaces with appropriate grasses which will also trap wind blown sand 4. establishing stabilising plants on loose surfaces

http://en.wikipedia.org/wiki/File:Beach_restoration_device.jpg

1

3/4

http://en.wikipedia.org/wiki/File:Helmgras_kijkduin_februari_2005.JPG

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Soft Engineering solutionsSoft Engineering solutions5. managed retreat - rebuilding coast inland and allowing natural flooding of defined areas to form salt marshes which then acts as a form of natural coastal defence for areas inland. http://en.wikipedia.org/wiki/File:Tolles

bury_bare_ground.jpg

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How does soft engineering stack up?How does soft engineering stack up?

AdvantagesAdvantagesThey are more environmentally friendlyThey tend to be cheaperThey look nicer

DisadvantagesDisadvantagesIf they are trying to, they slow up rather than stop erosionIt might be your house that gets sacrificed?

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What is the feature you can see on What is the feature you can see on this map?this map?

http://en.wikipedia.org/wiki/File:East_Riding_of_Yorks_outline_map_with_UK.png

© Copyright Stanley Howe and licensed for reuse under this Creative Commons Licence. It is called Spurn Head

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This Spurn This Spurn HeadHead

What 2 features can you see in the picture which might be helping the Head from moving on?What kind of engineering is each of them?What do you think is happening in the lower pictures?

© Copyright Stephen McKay and licensed for reuse under this Creative Commons Licence.

Crumbling sea wall   © Copyright Charles Rispin and licensed for reuse under this Creative Commons Licence.

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This is salt marshThis is salt marsh

Can you remember where that forms on a spit?How does it get there?

© Copyright Paul Glazzard and licensed for reuse under this Creative Commons Licence.