All About Waves
Coasts 1
Learning Objective
To understand how waves form and how they vary.
Success Criteria
• To explain how waves form.
• To describe the differences between constructive and destructive waves.
• To explain how longshore drift works.
Starter Discussion
In pairs, talk about the best
beach you’ve ever been to.
What did you do there?
What Even Is a Coast?
It may seem
obvious what a coast is,
but can you write down
a definition?
A coast is where the land meets the sea.
Waves
Waves are extremely important when
it comes to shaping the coast.
But how do they form?
The wind
blows over
the sea.
Wind against
water causes
friction.
The surface
water is
pushed in the
direction of
the wind.
A wave
is formed.
Some Waves Are Bigger Than Others
Key factors in the strength of the wave:
• The strength of the wind
• The fetch
The fetch is the distance the wind has
travelled across the sea.
Click to enlarge
Strong winds and a large fetch = powerful waves!
Recap
In pairs, discuss these two questions:
1. How do waves form?
2. What can make a wave bigger?
Wave Formation
What happens when waves approach the shore?
See if you can add the following labels to the Wave Formation diagram.
Use the Wave Formation Activity Sheet to create your own version
of this important diagram.
Prevailing wind
Wave length
Wave height
Crest of wave rises and steepens
Wave breaks
Increasing friction
Click to enlarge
Beach
Wave Formation
Did you put the labels in the correct place?
Make sure you have a perfect copy of the diagram!
Prevailing wind
Wave length
Crest of wave
rises and steepens
Wave height
Wave breaks
Beach
Increasing friction
Geography Dictionary!
Make sure you have a good understanding of these key terms.
sea:
A region of water within an ocean
or partly enclosed by land.
ocean:
A large body of salt water.
sediment:
Material which can be moved and
deposited elsewhere.
swash:
The movement of a wave up a beach.
backwash: The movement of a wave back
down a beach.
The Two Main Types of Waves
Constructive Waves
These help to build a
beach up by depositing
sediment like sand.
They construct the coast.
Destructive Waves
These remove sediment
from cliffs and beaches.
They are destructive.
Constructive Waves
Your aim is to make a detailed copy
of the
Swash
Constructive Wave illustration.
Your teacher will let you have a look at the
Backwash
diagram for 30 seconds, then you
have 60
seconds to make a start on your own diagram.
Low energy
You will get several chances to look at
wavesdiagram, but no pens whenever it’s on
the
Sediment deposited
display! on the beach
Get ready…
Increasing
friction
Wave energy absorbed
by the beach
Beach
Destructive Waves
Upper part of
cliff weakened
by salt spray
Your aim is to make a detailed copy of the
Destructive Wave illustration.
Your teacher will let you have a look at the
diagram for 30 seconds, then you have 60
seconds to make a start on your own diagram.
You will get several chances to look at the
diagram, but no pens whenever it’s on display!
Get ready…
Cliff attacked by
breaking waves
What is Longshore Drift?
This process continues and sediment
gets moved along the beach!
Sediment is carried up
the beach at an angle
with the swash.
It is called longshore drift.
The sediment travels with the
backwash down the beach in
a straight line due to gravity.
Waves approach the
beach at an angle
Longshore Drift
Groynes are sometimes
placed on a beach to stop
this from happening because
having sand on the beach is
a key method of stopping
coastal erosion.
Longshore Drift
On your Longshore Drift Activity Sheet, complete the diagram to show how
the process moves sediment.
Welcome to today’s edition of…
And here’s your host…
Stevie Starfish!
OK folks, let’s get
straight down to business!
I’m going to show you a word
or phrase, and you need to tell
me whether it’s linked to
Constructive or Destructive
waves. Got that?
calm weather
constructive
erosion
destructive
strong swash
constructive
sediment deposited
constructive
stormy weather
destructive
energy absorbed by beach
constructive