Lesley Monk Balfron High School Session 2005/6

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LITHOSPHERE CORE COASTLINES

Lesley MonkBalfron High SchoolSession 2005/6

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CONTENTSSlide-show 1-Coastlines of erosion

Slide-show 2-Coastlines of deposition

Slide-show 3-Coastlines of changing sea level

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MARINE EROSION PROCESSES.

Read the course booklet, page 11.

You will need to know and be able to explain the four methods of coastal erosion and two of weathering on the page.

The next few slides illustrate these processes.

These slide-shows are all on the Prepwork folder if you wish to copy any notes from them; we will not be stopping in class for you to do this

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LITHOSPHERE CORE COASTLINESThe 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.

Hydraulic Action

There is no separate picture for wave pounding!

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LITHOSPHERE CORE COASTLINESAbrasionRock 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.

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Wave attritionRock 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.

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Water- layer weatheringAlternative 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.

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Corrosion (solution)

Salts and acids in sea water can react with rocks , slowly dissolving them away.

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TEST YOURSELF!Match the processes with the description on the next slide by writing them out in your jotter. Write these ‘heads’ first, leaving a space of about three lines for each,to write in the tails…….

Hydraulic pressure is-

Corrasion is-

Attrition is-

Corrosion/solution is-

heads

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tails

-the chemical weathering of the cliff when salts and weak acids dissolve rock minerals.

-the sheer force of the waves as they crash into a cliff explode, compress the air, and cause the face to break up.

-the sandpaper effect when waves, armed with rocks and pebbles, rub away the base of the cliff.

-rocks and pebbles rub against each other on beaches forming smaller and smaller particles.

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Rates of erosion depend on many factors:

Waves – strength, frequency, heightWeather – frequency of storm conditionsGeology of the coastline :

-type of rock-orientation of stratification

(Copy this note into your jotters. Discuss the factors in class.)

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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!

Copy this note!

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LITHOSPHERE CORE COASTLINESThere are eight erosion-related features you need to learn up.

You need to be able to ;-

Describe them using their proper terms

Explain IN DETAIL how they form

Draw simple LABELLED SKETCHES of them

Give EXAMPLES of them in the UK.

BAY AND

HEADLAND

CAVE AND

BLOWHOLE

ARCH

STACK

STUMP

WAVE-CUT PLATFORM

NEEDLE

ABRASION

NOTCHES

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Read about them on pages 12-13 of the booklet, and answer the questions to help focus your attention on the most important factors.

Many erosion features are a result of rocks of varying hardness occurring beside/below each other. The DIFFERENTIAL EROSION between them creates the landform.

(Note that mass movements may also be triggered as a result. )

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LITHOSPHERE CORE COASTLINESQ1. 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.

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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.

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Headland erosion near Noss Point CaithnessThe sea is eroding this headland back leaving a wave-cut platform below the waves.

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LITHOSPHERE CORE COASTLINESHow Are Wave Cut Platforms Formed? (Copy this note into your jotter.)

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

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Cliffs and Wave Cut Platforms

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LITHOSPHERE CORE COASTLINESThere is a copy of this diagram to stick into your jotters. Add in the labels to your copy.

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Sea Inlet near Noss Point Caused by hydraulic action at a

weakness in the rock.

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Sea Inlet At Duncansby Head

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LITHOSPHERE CORE COASTLINESThere is a copy of this diagram to stick into your jotters. Copy the text onto your copy of this diagram.

Note;- for a cave to occur, there must be an area of weakness in the cliff face.

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Smoo Cave near Durness

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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 hightide in stormy weather.

Copy this note!

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LITHOSPHERE CORE COASTLINESThere is a copy of this diagram to stick into your jotters. Copy the text onto your copy of this diagram.

notches

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

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Natural Arch

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LITHOSPHERE CORE COASTLINESClose up of Duncansby Stacks and Stump

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Stack At Sandwood Bay

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MINI-HOMEWORK EXERCISE

Take a copy of the homework exercise. It is a feature- identification and explanation task.

Answer it on A4 sized paper, and hand it in for marking at the start of next lesson.

Please write it in ink or word- process it, proof-read it, and put your name on it!

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5 Suggested answers -available later!

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

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

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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.

soft

hard

You will learn the names of the rock types in the Case Study unit- Rural Land Resources.

The geology of Lulworth Cove Copy the diagram and explanation.

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Click on the hyperlink to see the video clip about Lulworth cove.

Add to your notes to make sure that you can answer a question about this feature in an exam.

HYPERLINK

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ORDNANCE SURVEY MAPWORK

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 !!

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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!

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LITHOSPHERE CORE COASTLINESYou 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

ABRASIONATTRITION

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

Lesley Monk Balfron High School Session 2005/6

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Transcript of Lesley Monk Balfron High School Session 2005/6