Coastal erosion processes

Quick check! Which erosion type? Write a catchphrase short answer to explain the process.

A

DD

CC

B

Hydraulic Action

CorrosionAttrition

Abrasion

Types of coastal erosion

Create four ‘Kung Fu’ actions to represent each coastal erosion process

The secret art of Coastal Kung Fu Fighting!

Hydraulic Action: make punching movements with hand- demonstrates force of water hitting cliff.

Abrasion: make a throwing gesture with hands like you are throwing dealing cards very rapidly

Attrition: make 2 fists, and then bring them towards each other, hitting each other, then open hand to resemble a

stone breaking.

Corrosion: have arms out stretched in front of you, waving fingers, and moving arms downwards. Sound effect of

something dissolving is needed.

Exam Q

• Name and describe two processes of erosion which affect cliffs.

• 1..........................................................................................................................................................................................................................................................................................................

• 2.......................................................................................................................................................................................................................................................................................................... [4marks] – 1 mark per named process, 1 per explanation

Coastal processes & features

Erosion

Why does erosion matter?

Video

Homework due1. Glue in & swap books

2. Evaluate each other’s work:

- Highlight where they use a keyword

- Smiley face where they include fact

- Sad face for a SPaG mistake

- Give them a comment at the end

e.g. ‘Great use of evidence to PROVE IT but next time describe the impacts better.’

No HW? Epic fail. Come collect your DT slip. Then sit and write in your No HW? Epic fail. Come collect your DT slip. Then sit and write in your book 5 reasons why doing HW is important.book 5 reasons why doing HW is important.

Rates of erosion depend on many Rates of erosion depend on many factors:factors:

• Waves – strength, frequency, heightWaves – strength, frequency, height• Weather – frequency of storm conditionsWeather – frequency of storm conditions• Geology of the coastline :Geology of the coastline : type of rocktype of rock degree of resistancedegree of resistance stratificationstratification stabilitystability

The geology of the coast affects how much it is eroded.

More resistant rocks (e.g. chalk) erode more slowly than less resistant rocks (e.g. clay, limestone)

Make a prediction – how will this headland look in 1000 years?

flickr

• Back-to-back

• Number 1 = Look. Describe what you can see in detail. No keywords.

• Number 2 = Close your eyes. Guess what the landform / feature / process is.

Answer these exam questions in your books using full sentences.

1) Describe the image (3 marks)2) How was this formed? (2marks)

3) What might the impact be on people? (2marks)

Coastlines of Erosion

1. Headlands and bays

2. Cliffs and wave cut platforms

3. Headland erosion and the formation of caves, blowholes, arches, stacks and stumps

The main landforms created by erosion are…

Headlands and bays• Caused by DIFFERENTIAL EROSION• i.e. where erosion happens at different speeds

• Headlands & bays are found in areas where alternating resistant and less resistant rock meets the coast at right angles

• Bays are formed when erosion erodes the softer, less resistant, rocks more quickly

• Headlands are formed of rocks which are more resistant to erosion, therefore erode more slowly

An example of headlands and bays on the Dorset coastline…

chalk

clay

limestone

Swanage Bay

HW O.S. Map of Ballard point, a headland on the Jurassic Coast.

What landform is this? …………What type of rock do you think this is made from? …………………..…. .........................................................What effect does this have?............. …………………………………………

What do you think the little black lines mean? ………………………… ………………………………………..What processes might be happening here? …………………… …………………………………………

What landform is this? …………What type of rock do you think this is made from? …………………..…. .........................................................What effect does this have?............. …………………………………………

Wave cut notches and platforms

Wave erosion is greatest when waves break against the foot of the cliff.

1.Wave energy (hydraulic action mostly) undercuts the foot of the cliff to form a wave cut notch

2.Over time this notch enlarges due to attrition and hydraulic action. Eventually the cliff above it cannot be supported and so collapses under gravity.

3.As this is repeated, the cliff retreats inland. The collapsed material at the base of the cliff forms the Wave cut platform which will be eroded smooth over time by abrasion.

Wave-cut platform –Burgh Island, Devon

Wave cut platform Southerndown, South

Wales.

Coastal cake craft challenge

• RESOURCES = cake, sweets, whiteboard, A3 paper, pens, flip cam, iPhone

• CHALLENGE = explain how a wave cut platform is caused, using keywords. Produce a resource to explain the process.

RULES:No eating until AFTER you have shown your resource and completed the exam

Q.

Wave cut platforms

• Copy the exam question into your books, then answer it:

“With reference to erosion processes, explain how wave-cut platforms are formed” {4marks}

Using the terms below, produce a four picture storyboard

explaining the process that produces a wave cut platform.

High TideLow Tide

Wave Cut Notch

Abrasion

Retreat

Wave cut platform

Cliff

Gravity

Hydraulic action Attrition

Tony Cassidy

1

High Tide

Low Tide

Attrition & hydraulic action occurs between high and low tide- rocks are

hurled at the base of the cliff & water forced in to

cracks.Tony Cassidy

2

Wave Cut Notch

Eroded material

available to take part in corrasion.

Cliff is undercut, leaving it unstable.

3

Cliff retreats

Wave Cut Platform-

Abrasion can not occur below low

tide.

Wave Cut Notch

The process of hydraulic

action will continue…

4

Cliff retreats

Wave Cut Platform.

How have coastal processes shaped this landform? (4 marks)

Caves

Arches

Stacks

and

Stumps

Caves, arches, stacks and stumps

CavesCaves usually develop from widening and deepening of notches where there are weaknesses in the cliff

Here you can see the fault – this will enlarge to a cave

Erosive waves may blast their way vertically through lines of weakness in the roofs of caves.

This produces a blowhole on the cliff top.

In stormy conditions sea spray may spout from blowholes.

BlowholesBlowholes

Arches

These are formed by the wearing away of narrow headlands often by two back-to-back cave systems joining.

Durdle Door

The waves continue to erode at the foot of the arch widening it. Eventually the roof of the arch can no longer be supported and it will collapse under gravity.

We can now imagine how the headland at Durdle Door might be evolving

Durdle Door in Durdle Door in the past………the past………

Durdle DoorAs it is at present ………

Durdle DoorDurdle Door

…sometime in the future?

Stacks and stumps

Stacks often represent the seaward Stacks often represent the seaward remnant of a collapsed arch. These tall, remnant of a collapsed arch. These tall, isolated pillars of rock such as ‘The isolated pillars of rock such as ‘The Pinnacles’ on the Dorset coast, are Pinnacles’ on the Dorset coast, are reduced by further wave action to reduced by further wave action to stumps.stumps.

CASE STUDY EXAMPLE: Old Harry Rocks in Dorset

1. The waves erode FAULTS (cracks) in the headland.

2. The waves eventually erode through the headland to form an ARCH.

3. The arch becomes unsupported and collapses to form a STACK.

4. A STUMP is formed from the collapsed stack.

C DBA

Match the image with the most appropriate label.

If these photos were taken of one headland over time, which of these landforms would be the first to be formed?

1 2

3 4

1 2

3

4

This is a cave (‘Stair Hole’).

This is an arch (‘Durdle Door’).

This is a stack (Old Harry’s Rocks). These are stumps.

Dear John letter

• Write a letter in the style of ‘Dear John’ between the features of erosion

• E.g. between a stack and a cliff, or a bay and a headland, or a platform and a cliff

e.g.

Case Study : Jurassic Coast, Dorset

Jurassic Coast

• Using the maps above, describe the location of the Jurassic Coast. Use evidence from the map. [3marks]

N

The Jurassic Coast

• The Jurassic Coast is a section of coastline in Southern England that shows geology over millions of years.

• The coastline first began forming 250million years ago

• Dorset shows the geology of the Jurassic period, between 200-140million years ago

Bays + Headlands at Swanage

Lulworthcove

• Lulworth Cove, Dorset, has a geology which is a mix of different rocks which have been tilted upwards over the years to become nearly vertical.

• Millions of years ago, a river rain through the rocks to the sea. This allowed sea water to enter + erode the rocks inland.

• First an opening in the limestone was eroded, then the sea reached the softer rocks of clay and sands and very quick erosion happened, spreading outwards.

• Eventually, the sea eroded far back in to the land until it reached the resistant chalk. Here the erosion slowed down. This made the perfect horseshoe-shaped bay you can see.

• Eventually this cove will erode further back and join another cove, to form one massive bay.

Lulworth Cove

Stair Hole, left. Lulworth Cove, Dorset right and below

Lulworth Cove is a horseshoe shaped bay that formed because the inland rocks are less resistant than the headland.

Differential erosion because of geology.

http://www.youtube.com/watch?v=ZWEJq03NBao

Summary revision video

Playdoh time

Having heard about how these erosional landforms are created….….in true Blue Peter style in your groups you are now going to create your own models to show the formation of these landforms along a cliff headland.

Using the pens, add the following labels to your features;

Wave Cut Platform

Wave Cut Notch

Stack Stump

Cave Fault

Arch Headland

Using the post-it notes, add explanations as to how these features were created.

Include types of erosion

NOW COPY THIS AS AN ANNOTATED SKETCH INTO

YOUR EXERCISE BOOKS

How does geology influence erosion?

O.S. Map of Ballard point, a headland on the Jurassic Coast.

What landform is this? …………What type of rock do you think this is made from? …………………..…. .........................................................What effect does this have?............. …………………………………………

What do you think the little black lines mean? ………………………… ………………………………………..What processes might be happening here? …………………… …………………………………………

What landform is this? …………What type of rock do you think this is made from? …………………..…. .........................................................What effect does this have?............. …………………………………………

Old Harry Rocks

What landform is this?

What process might have

happened here?

Durdle Door Arch in Dorset

What landform is this?

How was this formed?

The Needles, Isle of Wight

What landforms are these?

How were they formed?

Birchington-on-Sea

What landform is this? How did it

form?