Lesson video

Hi there.

I'm Ms. Roberts.

Welcome to this geography lesson with me today, which is from our unit of work all about coasts.

This unit is investigating what shapes life at the coast, and today's lesson is all about the natural processes that help to shape the coastline itself.

By the end of the lesson today, you are going to be able to name some of those processes, and you'll be able to describe how they help to give our coastlines shape.

Let's begin by looking at some key words for today's lesson.

These are words that you are going to hear a lot, and you need to be able to use yourself when you are talking about the coast.

Today's first key word is processes.

We are thinking specifically about processes that happen at the coast, natural processes, but processes can happen anywhere and in many different ways.

A process is essentially an ordered sequence or series of actions, events, or changes that make something happen.

Think about baking a cake.

First, we need to mix all the ingredients.

Then, we need to put the cake into the oven to bake, and then we have a cake.

That is a process.

The next three key words are types of coastal processes.

You're going to be finding out a lot more about these as we go through the lesson today, but as an introduction, we have erosion, which is the process whereby the Earth's surface, whether that is rock or soil or any other natural material, is worn away and then it's transported somewhere else.

Transportation is the next process, and that's when water, in this case at the coast, moves sand, mud, or rocks from one place to another.

And our final process then is deposition, and that's when the material, such as sand, mud, or rocks that we just described, is dropped by the water that was carrying it.

It's deposited.

So let's get started now with the first half of today's lesson, and we're going to begin by investigating coastal processes, and, in particular, erosion.

As we heard, there are three main processes that take place at the coast, which help to give our coastlines the shape that they have.

Those processes are erosion, transportation, and deposition.

So if you look at the photograph here of this beautiful coastline, you can see a golden sandy beach, and you can see cliffs and rocky outcrops.

They are all there because of these three processes, and that's what we are going to look at today.

Erosion is the process whereby rock or soil or sand or any other natural material is worn away and broken down.

In this case, we are thinking of the erosion of our coasts.

This erosion shapes and changes how the coastline looks.

Some coasts are very uneven, some coastlines are very flat, but how do these changes take place? What exactly is erosion, and how does it happen? We're going to be finding out.

Before we move on though, let's stop and have a quick check to make sure we've all been following so far with this multiple choice question.

I want to know what is erosion? Is it A, the process of rock or soil being added to a beach, is it B, the process of rock or soil being moved along a beach, or C, the process of rock or soil being worn away and broken down? Make your choice now.

Have you decided? Erosion is, of course, the wearing away and breaking down of rock or soil.

That's option C.

Well done if you spotted that correctly.

So now, we're going to look in some more detail at erosion and the processes that are involved within it.

There are actually four different types of erosion that take place at the coast.

These are abrasion, hydraulic action, solution, and attrition.

You may not have heard of any of those terms before, but don't worry, I'm going to explain what they all are right now, and I'm going to show you some diagrams to help you understand how they work.

It's those processes of abrasion, hydraulic action, solution, and attrition that each contribute to the wearing away of the cliffs and the rocks at the coast.

When those cliffs and rocks are worn away by these processes of erosion, they begin to change and create special, unique coastal land forms, such as arches.

You can see an arch here in this photograph.

It looks like someone might have just stuck that arch onto the front of the cliff face, doesn't it? But that's actually a result of erosion.

Okay, before we look at these processes in detail, can you tackle this question for me? Here is a statement about coastal erosion.

There's a mistake in it though.

I need you to find the mistake and correct the statement.

Listen carefully.

The four types of erosion are abrasion, attrition, solution, and hydraulic acid.

What's wrong with that statement? Have you spotted the mistake? Well done.

The statement should say the four types of erosion are abrasion, attrition, solution, and hydraulic action, not hydraulic acid.

That's something you might hear more about in chemistry.

So let's find out some more now about how these individual processes work.

Let's begin with the first process, which is abrasion.

Now, abrasion is to do with pieces of rock or other material, sand, stones, that are being carried by the wave.

They've been scooped up by the wave, and when they smack into the cliff or the rock at the coast, as they do this, they wear that rock face down, the constant hitting and banging of those rocks within the wave against the cliff face.

Eventually, this causes the cliff face to start to break down and other small pieces of rock begin to fall away from the cliff face as a result of the abrasion taking place.

The process of hydraulic action also takes place in a similar way, as the waves constantly crash against the cliff face.

Any cracks that are there on the cliff have air forced into them at that moment.

When the air is forced into the cracks, the cracks become wider, and as they become wider, they become weaker.

And as you can see, some of those cracks start to expand, and other cracks begin to form.

This process is ongoing, and it causes the rocks to break down, and eventually break away from the cliff.

Next, we have the process of solution.

Now, it might look to you like that line is just pointing to the water.

There's nothing there.

There's nothing to see.

That's because the water is also carrying some particles that are so tiny, they're not visible to the naked eye.

These are particles of rock that have been dissolved into the water.

They are still there, but we can't see them.

That is solution, when rock is dissolved by seawater.

Some particular types of rock, like limestone and chalk, are more vulnerable to this type of erosion.

And what was the final process? What was the fourth process? Can you remember? It's another one that begins with A.

It's attrition.

This is also to do with the rocks being carried within the water itself.

So this is not about erosion happening at the cliff face.

This is about erosion happening within a wave.

Those rocks and stones that are being carried are bumping into each other as they are being carried along.

As they bump into each other, they break and form smaller pieces, which then continue to get bounced about, and they crash into each other, and they become smaller, so there is an ongoing process of rocks bouncing about, and being eroded within the wave.

Okay, let's bring all of that new knowledge together now and try a little check to see if we can accurately describe those four processes.

The four processes are named here for you on the left, abrasion, attrition, hydraulic action, and solution, and on the right-hand side, we have descriptions.

You can pause the video while you do this, read the descriptions, and match each one to the correct process.

If you're not sure about one, try moving on and reading the next one, and then going back.

Pause the video now.

Okay, have you matched all of those up? Let's check.

First, we have abrasion.

That is when the rocks in the waves are knocking against cliffs.

Then, we have attrition.

Attrition is when the rocks in the waves knock against each other.

Make sure not to muddle those two up.

Those words are very similar, aren't they? Let's move on to hydraulic action.

This is when waves force air into cracks on the cliffs.

And finally, solution is dissolving rocks.

That's when rocks are dissolved by the seawater.

So there are lots of processes happening at the coast, and each of those four processes is part of this large process that we call erosion.

So let's move on now to an activity to make sure that we really cement this new learning.

I need you to name and label the processes that are happening at each point marked in this diagram.

The processes are listed there for you.

After you've done this, I want you to choose one of those processes, any one of your choice, and explain how it contributes to the erosion of coastlines.

Pause the video now while you complete this activity.

Ready? Great.

I'm going to share the answers with you now.

First, let's look at labelling these processes.

A is hydraulic action, the air being forced into the cracks, B is abrasion, those rocks knocking against the cliff, C is attrition, rocks knocking against each other, and D is solution, rocks that have been dissolved by the seawater.

One of the Oak Academy children have given us an example answer to read here, and this is about hydraulic action.

Hydraulic action is a type of coastal erosion.

It happens when waves crash against rocks and cliffs.

Strong waves force air into tiny cracks in the rock.

This causes the crack to expand, and the rock around the crack becomes weaker.

Eventually, pieces of weak rock break down and can come away from the cliff.

This process can change and shape what coastlines look like.

I think that's a great description of hydraulic action.

So you may recall from the start of this lesson that erosion isn't the only process happening to shape our coastlines.

There are two other processes called transportation and deposition, so we're going to move on and look at those now.

Transportation happens when that material we've just seen being eroded is moved from one place to another at the coast.

That material can include rocks and stones, small particles of sand and mud, and don't forget those tiny particles that have been dissolved by solution and we can't even see.

You can see a range of material that's been transported here in this photograph.

We have sand, we have very small pieces of rocks and stones, and then some larger pebbles as well.

Just as we have looked at four types of erosion, there are actually four processes of transportation as well.

These are called traction, suspension, solution, and saltation.

Traction, suspension, solution, and saltation.

Were you listening carefully to those? I hope so.

Try this question.

Which of these is not a type of transportation? Saltation, traction, attrition, or suspension.

Think carefully.

It's attrition.

Attrition is a type of erosion.

That's the erosion that happens when rocks in a wave crash into each other.

This diagram will help you to understand the processes of transportation that are happening at the coast.

First, you can see here some small particles of rock that are floating along in the water of the sea.

Suspension is when small, light particles are carried along.

It's simply that.

They are floating along in the sea.

As the sea moves, those small particles move with it.

Solution, as you know from erosion, is when rocks are dissolved.

So solution is those dissolved materials being moved along with the seawater that dissolved it.

The next two processes are about larger particles.

Traction is to do with the largest particles.

So if you look at this diagram, you can see that the largest rocks here are involved with traction.

Traction is when those heavy stones and rocks are dragged along.

They are dragged because they are heavy.

So as the wave and the seawater moves, those heavy rocks are dragged fairly slowly in comparison to the lighter particles that are floating above them.

They are dragged along the seabed.

Moving along to these rocks, however, these rocks are not quite as big and heavy as the rocks involved in traction, and they are not quite as small or light as the rocks involved in suspension.

Saltation is when these medium-sized rocks and pebbles bounce along the seabed as the waves move above them.

They aren't heavy enough to need to be dragged along the seabed.

They are light enough to bounce along and bounce along as the seawater moves around them.

Okay, so let's see if we can put that new learning to the test now.

Again, here, we have the types of transportation listed on the left.

We have traction, suspension, saltation, and solution, and then the descriptions are on the right.

I would like you to match the processes to the descriptions.

You can pause the video now while you do that.

And again, if you're stuck on one, move on to the next one, and then come back to it.

Pause the video now.

Okay, have you got them all matched up? Great.

Let's take a look at the definitions together.

First of all, traction.

That's the dragging of those large and heavy rocks along the seabed.

Suspension is when those small rocks are floating along in the seawater.

Saltation is the medium-sized rocks that bounce along as the waves move across.

And solution is the dissolved rocks that are being carried in the seawater that dissolve them.

Great work.

Well done.

Okay, so as well as transportation, we need to think about the next step, which is deposition.

All of that material that we've just seen that is being transported by the waves, that's called its load.

Loads can be quite heavy, and waves need lots of energy in order to be able to carry them.

If a wave doesn't have enough energy, it can't carry its load, and that is when deposition happens, when waves lose their energy.

This is a picture of a coastal area where lots of deposition is happening.

The process of deposition is when material is added to parts of the coast because it's dropped by the wave.

The material that has been eroded somewhere else, it's been transported along by the seawater and by the waves, and then the wave loses its energy, and that load is deposited in another area, and this adds material, such as sand, to the coast.

You can see in this picture here how there is a long narrow ridge of sand sticking out.

That's where sand has been deposited and deposited and deposited again, reaching further and further out from this coastline.

So thinking about that process of deposition, is this statement true or false? The process of deposition takes material away from the coast.

What do you think? True or false? This statement is false.

And why is it false? It's false because deposition happens when waves lose their energy and drop the load that they are carrying.

So all of that material that was in their load is added to the coast there where it is dropped.

It's not removed.

It's added.

Here is an activity for you now about these processes of transportation and deposition.

First, you have the diagram there, which shows you those different processes of transportation.

They're labelled A, B, C, and D.

I would like you to name them.

After you have done that, I would like you to select one of those processes, perhaps a couple of them if you finish quickly, and explain how that process transports material that has been eroded from the coast.

Pause the video now whilst you complete this task.

Okay, let's review these answers together.

First of all, let's name these processes.

Process A, we've got particles floating in the water there.

That is suspension.

B, we've got the largest rocks in the diagram involved in this process.

That's traction.

C, these particles might be so small that we can't see them.

That's because this is solution.

And finally, the one we are left with is saltation.

This is those medium-sized particles that bounce along the seabed.

And for part two, I've got an example answer here from one of the Oak Academy children, and this is about saltation.

It says that saltation is a type of coastal transportation.

That's a great place to start.

It happens when medium-sized pebbles or stones bounce along the seabed.

The movement of the waves gives them the energy to bounce along.

Well done.

So that brings us to the end of this lesson about the processes that help to shape our coastline.

We've found out that natural processes that happen at the coast are what gives it its shape.

There are four types of erosion that happen at the coast.

They are abrasion, hydraulic action, attrition, and solution.

There are also four types of transportation happening at the coast.

That's traction, solution, suspension, and saltation.

Deposition is another process that happens at the coast, and that happens when waves lose their energy and can no longer carry their load.

It is due to the combination of all these processes happening that gives us our beautiful coastlines, our sandy beaches, arches, and other coastal land forms. Join me again for another lesson about coasts to find out more.

See you next time.