Lesson 3: Waves and Coastal Landforms

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Lesson 3 Waves and Coastal Landforms

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

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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?
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Starter

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

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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

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What happens below the water as waves move?
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What happens when waves reach the coast?
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Wave Types

• We 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

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Task

• You will need to understand how waves are formed
  and effect the coastline.
• Answer the questions below to check your
  understanding of this.

• The sea causes three processes to occur on the
  coastline, name these and give a description of
  each.
• What are the three characteristics that effect
  the size of a wave?
• Explain the difference between swash and
  backwash.
• Explain how constructive waves construct
  coastline and destructive waves destroy it.
• Complete the activity Your questions-page 77
  GCSE Geography.

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Landforms at the Coast

• Marine and Sub-Ariel erosion cause several
  landforms and erosional features at the coast.
• Headlands and Bays
• Caves, arches, stacks and stumps
• Cliff slumping
• Wave cut notches and platforms
• Longshore drift creates depositional landforms

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Headland and Bay formation
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Caves, arches, stacks and stumps
Source http//www.geography.learnontheinternet.co
.uk/topics/waves.html
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Durdle Door- How was it formed?
What is the influence of joints and faults on
this landform?
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Wave-cut notch and platform
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Wave-cut notch and platform
Wave cut platform
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Task Make a copy of this diagram in your book,
remember to include a title.
1
3
2
7
6
5
4
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Longshore Drift- process of deposition and
transportation
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Lets try the Long Shore Drift dance

• Up the beach at an angle
• Swash
• Straight down the beach
• Backwash

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Task describe and explain the process of
longshore drift (6). You may use a diagram to
help.
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Landforms created by Longshore Drift
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How are spits and bars formed?
Task Draw and label a spit. Use page 74 of the
text book to explain how a spit can develop into
a bar.

• 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.

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Plenary

• Lets 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)