Lesson 3: Waves and Coastal Landforms

Objective:To explain how waves are formed and how wave action erodes cliffsTo look at wave types and their influence on the beach profileTo look at longshore drift and the landforms it createsTo be able to describe some of the landforms created by hard and soft rock

MARINE EROSION (cliff foot) Erosion is the process of wearing away and breaking down rocks.

Abrasion – the waves throw pebbles and rocks against the cliffs, wearing them away

Attrition – the pebbles and rocks are worn away as they crash against each other.

Solution – the water itself is slightly acidic and can dissolve minerals such as calcium carbonate, which is in chalk and limestone.

Hydraulic Action – the force of waves traps air in cracks …air pressure breaks off pieces of rock…

How else can we remember these?

StarterWhich type of marine erosion goes with these definitions.

1. When rock fragments grind and bash into each other down into smaller smoother pebbles, shingle and finally sand which is later deposited as beaches.

4. Lots of sea water crashes against the land, and air and water are trapped and compressed in rock surface cracks. When the sea moves away again, the air expands explosively weakening the rocks, enlarging the cracks and breaking pieces off.

2. Is cause by broken rock fragments battering the land, cliffs etc. and breaking off other pieces of rock.

3. Involves chemical action of sea on rock. If the rock is limestone, it dissolves in the sea-water – some sea salts can also react with certain rocks and cause them to rot.

Waves and the Coastlines

Waves are constant Waves have three affects on the coast

They cause Erosion

They Deposit eroded material

They Transport eroded material

Waves The height of the waves depend on how long and

far the wind has been blowing over the sea and how strong it is. This is called the fetch

What happens below the water as waves move?

What happens when waves reach the coast?

Wave TypesWe know what waves can do to the cliffs but did

you know that there are 2 different types of waves and they can BUILD or DESTROY beaches.

Destructive waves these destroy beaches by taking away the sediment- also known as winter waves

Constructive waves these build beaches by depositing sediment on the beach- also known as summer waves

TaskYou will need to understand how waves are formed and

effect the coastline.Answer the questions below to check your

understanding of this.

1. The sea causes three processes to occur on the coastline, name these and give a description of each.

2. What are the three characteristics that effect the size of a wave?

3. Explain the difference between swash and backwash.

4. Explain how constructive waves construct coastline and destructive waves destroy it.

5. Complete the activity ‘Your questions’-page 77 GCSE Geography.

Landforms at the CoastMarine and Sub-Ariel erosion cause several

landforms and erosional features at the coast. Headlands and BaysCaves, arches, stacks and stumpsCliff slumpingWave cut notches and platforms

Longshore drift creates depositional landforms

Headland and Bay formation

Source: http://www.geography.learnontheinternet.co.uk/topics/waves.html

Durdle Door- How was it formed?

What is the influence of joints and faults on this landform?

Wave cut platform

Task:Task: Make a copy of this diagram in Make a copy of this diagram in your book, remember to include a your book, remember to include a title.title.

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Longshore Drift- process of deposition and transportation

Let’s try the Long Shore Drift dance

Up the beach at an angle =

Swash

Straight down the beach=

Backwash

Task:Task: describe and explain the describe and explain the process of longshore drift (6). You process of longshore drift (6). You may use a diagram to help. may use a diagram to help.

Landforms created by Longshore Drift

HOW ARE SPITS AND BARS FORMED? Spits are sand or pebble beaches

joined to the land at one end. They are features of coastal deposition and tend to be formed by longshore drift.

Most extend at a gentle angle out to sea or grow across a river mouth.

Many spits have a hooked or curved end.

The shallow sheltered area behind the spit fills with mud. This is called a salt marsh.

Spits develop in places where: Longshore drift moves large amounts if

material along the beach. There is a sudden change of direction of

the coastline. The sea is shallow, sheltered and calm.

Task:Draw and label a spit. Use page 74 of the text book to explain how a spit can develop into a bar.

PlenaryLets play Geography Pictionary! You will be given a feature or process and you

need to draw it for the others to guess.

Describe and explain the process of longshore drift. (6marks)

Choose a landform, explain how it can develop over time. (6 marks)