1. Hydraulic Action
The force of waves hitting a cliff (or sea wall) compresses water and air into cracks and joints.
This increase in pressure may lead to cracks widening and pieces of rock breaking off.

2. Abrasion
Rock fragments may be picked up by waves and thrown against the rock face of cliffs by subsequent waves.
Sometimes the softer strata are abraded more than the harder ones, giving a striped appearance.
Abrasion is most effective at the base of cliffs.

3. Wave attrition
Rock fragments are worn down into smaller and more rounded pieces.
Currents and tidal movements cause the fragments to be swirled around and to grind against each other.
This type of erosion produces pebble beaches.

4. Water- layer weathering
Alternative wetting and drying -as happens with the rise and fall of the tides -can disintegrate porous or coarser rock layers.
Salt crystals growing in rock spaces can do the same thing.

5. Corrosion (solution)
Salts and acids in sea water can react with rocks , slowly dissolving them away.

6. Rates of erosion depend on many factors:
(Copy this note into your jotters. Discuss the factors in class, you can use your textbook to help.) 10 mins
Waves – strength, frequency, height
Weather – frequency of storm conditions
Geology of the coastline :
-type of rock
-orientation of stratification

7. The FETCH is the distance travelled by waves from one shore to another.
The waves hitting the southwest coast of England have a fetch of about ten thousand miles!

8. CONSTRUCTIVE AND DESTRUCTIVE WAVES
Constructive waves These are low energy waves which transport grains of sediment and deposit them on beaches. This type of wave is common in the summer.
Destructive waves These are high energy waves which erode sediment from the beach and deposit material further along the coast. They mainly occur during winter and autumn storms.
Constructive and destructive waves

9. SWASH AND BACKWASH
Waves break and push sediment obliquely up the beach (SWASH)…
… but the returning flow is straight down the beach at right angles to the shoreline (BACKWASH) .
Swash and backwash

10. Class work
Use both you textbook( ) and Wider World book ( ) to help you draw diagrams and explain the formation of:-
Headlands and Bays
Cliffs, Wave cut notch, Wave-cut platform
Cave, arch, stack, stump and geos
Blowhole

11. Q1. What two properties of a headland tell us that the rock is hard?
A. It juts out into the sea and is high ground.
Q2. What two properties of a bay tell us that the rock is soft?
A. It eats back into the land and is lower ground.
Q3. On a new cliff coast, what is the first feature caused by erosion?
A. Abrasion notches are created initially.

12. Q4.Cliff retreat creates which feature all along the coast?
A. It creates a wave-cut platform.
Q5.Why is this only exposed at low tide?
A. Erosion only happens between high and low tide marks, and no erosion takes place below LTM. The ‘top’ of the eroded cliff is the WCP, seen only when the tide is lowest.

13. Headland erosion near Noss Point Caithness The sea is eroding this headland back leaving a wave-cut platform below the waves.
Waves continually change the shape of the coastline around Britain. Headlands such as this are produced where the rock type is hard and resistant to erosion and bays where the rock type is softer and deposition dominates. In this slide the sea is a powerful agent of erosion. A scree of eroded rocks can be seen at the base of the cliff and a wave cut platform is visible showing where the previous cliff line was.

14. How Are Wave Cut Platforms Formed?
Erosion is greatest when large waves actually break against the foot of a cliff.
The foot of the cliff is undercut to form a wave cut ( abrasion) notch.
As the notch gets larger the cliff above becomes increasingly unsupported and in time collapses ( often by a mass movement process!)
As this process continues the cliff will slowly retreat.
The flat land left at the foot of the cliff is called a wave cut platform

15. Cliffs and Wave Cut Platforms

16. You should have copied this diagram from the Wider World Book into your jotter.1

17. Sea Inlet near Noss Point Caused by hydraulic action at a weakness in the rock.
Sometimes the sea can erode the areas of weakness in a cliff line producing long sea inlets such as this.

18. Sea Inlet At Duncansby Head
The horizontal bedding planes of sandstone are clearly visible but the sea has exploited the vertical joints in the rock to produce this inlet.

19. There is a copy of this diagram you should have copied from the Wider World book
Note;- for a cave to occur, there must be an area of weakness in the cliff face. 2

20. Smoo Cave near Durness
When the sea continues to erode weaknesses at the base of a cliff caves such as this can result.

21. A Blowhole or ‘gloup’ may form if the erosion at the back of the cave breaks through the roof to the top of the cliff. This usually happens at high tide in stormy weather. Copy this note!

22. There is a copy of this diagram you should have copied from the Wider World book3
notches

23. An arch forms when the sea breaks through to the other side of the headland.

24. Natural Arch

25. Close up of Duncansby Stacks and Stump
Stacks are continually eroded by the sea until they are reduced to stumps.

26. Stack At Sandwood Bay

27. Coves are a special feature and we will learn about them by looking at a case study of Lulworth Cove.

28. Lulworth Cove was formed by differential erosion
Lulworth Cove was formed by differential erosion. The next slides will explain how this happened.

29. Copy the diagram and explanation. The geology of Lulworth Cove
The hard rock at the coast has been breached. The sea can now get in to erode the softer rock behind, creating the cove. The second layer of hard rock stops the cove growing much larger.
hard
soft
You will learn the names of the rock types in the Case Study unit- Rural Land Resources.

30. ORDNANCE SURVEY MAPWORK6
You need to be able to recognise coastal erosion landforms from a map.
To practice this skill, take a copy of the question sheet and the two O.S. maps and tackle the questions.
THEY ARE NOT ALL EASY !!

31. As you go through the next (revision) slide, for each feature mentioned, look back through your unit booklets and this presentation. You are looking for named examples of as many features as possible.
Perhaps you could work in pairs to do this task!
THEN PLAY THE COASTLINE DOMINOES GAME!

32. You have now completed the erosion section.
You should be familiar with the following terms and be able to define and use them in your answers. Copy this.
PROCESSES
SOLUTION
WAVE POUNDING
ABRASION
ATTRITION
HYDRAULIC ACTION
WATER-LAYER WEATHERING
FEATURES
BLOWHOLE ARCH
NEEDLE CAVE
STUMP STACK
COVE INLET
BAY AND HEADLAND
NOTCHES
WAVE-CUT PLATFORM
RELATED TERMS
FETCH
STRATIFICATION
ROCK ORIENTATION
DIFFERENTIAL EROSION