Transcript Lesson 2: 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
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?
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.
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.
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.
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 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
Task
 You 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 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
Headland and Bay formation
Caves, arches, stacks and stumps
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 notch and platform
Wave-cut notch and platform
Wave cut platform
Task: Make a copy of this diagram in your
book, remember to include a title.
1
3
2
6
4
5
7
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: describe and explain the process of
longshore drift (6). You 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.
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)