1 Revision 1

2 This is what we need to talk about 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

3 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

4 Water erosion by waves. What can you see here?

5 This shows that the sand has been transported and deposited What can you see and why is it like that?

6 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.

7 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

8 Erosion 1 Attrition 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

9 Erosion 2 Abrasion occurs when rocks and stones carried by the waves wear away the base of the cliffs

10 Erosion 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

11 Erosion 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

12 Transportation 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 else its load. These materials are known as its load. The load is carried along by four processes.tractionsaltationsuspensionsolution

13 Transportation 2 Traction is where boulders or stones are rolled along the ocean-bed by the force of the water

14 Transportation 3 Saltation is when small pebbles bounce along and leapfrog over each other.

15 Transportation 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!

16 Transportation 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!

17 Deposition their load A waves drop their 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 water waves enter a sheltered area there is little wind

18 Match the word to the definition Attrition Abrasion Hydraulic action Corrosion Traction Saltation Suspension Solution The water dissolving away the cliffs The force of the water wearing away the cliffs Tiny particles of clay or sand being carried away by floating in the waves Rocks hitting each other, breaking pieces off, making them smaller and smoother Rocks wearing away the coast line Langer boulders being dragged along the floor of the ocean Dissolved chemical being taken away by the wave Smaller pebbles leapfrogging over each other as they move

19 Can you sort the words we have learnt into erosion and deposition? Try here!! bin35961TESTER.htm bin35961TESTER.htm

20 Changes in the shape of the coast

21 Next 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?

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

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

24 How cliffs are eroded wave-cut platform Over time the cliff retreats leaving a wave-cut platform just below the surface, that show when the tide is out This is in Dorset near Purbeck at Kimmeridge Bay.

25 There are some special coastal features 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.

26 cliff

27 crack

28 cave

29 arch

30 stack

31 stump

32 Some examples Old Harry’s Rock

33 Direction of swash Backwash Longshore Drift Long shore drift The waves are blown in at an angle and ‘swash’ the pebbles up the beach The water ‘backwashes’ down the quickest way taking the pebbles with it – So the sand and pebbles are moved from left to right

34 Direction of swash Backwash Longshore Drift Long 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 ……

35 And this happens if the long shore drift 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

36 What can happen with longshore drift? The sand and shingle are dragged down the coast from the NW. The blue line shows a shingle bank tombolo. It continued across the gap between the main land and the island to form a tombolo.

37 But in some places our coast is disappearing! What can we do? nphoto.com/ Erodedcliffp acifica.jpg Erodedcliffp acifica.jpg ‎

38 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?

39 Coastal Management Rapid 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 Coast 2. Pre-planning 3. Do-Nothing

40 Building structures Can be divided into 2 types Hard Engineering These 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 Engineering These methods try not to disrupt the environment and tend to be used where the environment is more important than say a town or road

41 Hard Engineering solutions 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)

42 Hard 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).

43 Would you have these? Advantages They all manage to absorb the energy from the waves and so reduce erosion They are long lastingDisadvantages They are not environment friendly They are not pretty They are expensive What if anything could make a home here? 07_riprap_photo.jpg

44 Soft Engineering solutions 1. beach renourishment - addition of sand or gravel to a beach to restore former levels 2.fencing - to reduce wave scour and promote sand deposition and to trap and accumulate wind blown sand 3. 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 Beach_restoration_device.jpg 1 3/4 ras_kijkduin_februari_2005.JPG

45 Soft Engineering solutions 5. 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. bury_bare_ground.jpg

46 How does soft engineering stack up? Advantages They are more environmentally friendly They tend to be cheaper They look nicerDisadvantages If they are trying to, they slow up rather than stop erosion It might be your house that gets sacrificed?

47 What is the feature you can see on this map? with_UK.png © Copyright Stanley Howe and licensed for reuse under this Creative Commons Licence.Stanley Howe reuseCreative Commons Licence It is called Spurn Head

48 This Spurn Head 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.Stephen McKayreuseCreative Commons Licence Crumbling sea wall © Copyright Charles Rispin and licensed for reuse under this Creative Commons Licence. Charles RispinreuseCreative Commons Licence

49 This 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.Paul GlazzardreuseCreative Commons Licence