Lesson video

Hello, geographers.

It's Mr. Robertson here, and I am so excited to be introducing our second lesson in our unit of work, Rivers: what's special about them? I love geography, and this is going to be the second lesson in our Rivers unit.

Last lesson, we introduced ourselves to rivers and some key terms about a river system.

Today's lesson is called River Processes and Landforms, and we're going to be investigating more about rivers.

So, geographers, we need to have on our geography caps, let's make sure we've packed our explorer rucksacks, and because we're learning about rivers, we need to make sure we have our explorer wellies on as well so we don't get too wet.

Let's find out about what we're learning today.

By the end of this lesson, you will be able to describe processes happening in a river and the landforms that they create.

As always, we have some key words today.

There are four key words in this lesson.

I'm going to say the words first, and I'm gonna ask you to repeat them back to me.

Are we ready? So our first word is erosion.

Fabulous.

Our second word is transportation.

Amazing.

Our third word is deposition.

Amazing.

And finally, landform.

Brilliant, geographers.

So let's find out what some of this geographical vocabulary means, shall we? So erosion is the process of Earth's surface, for example, rock or soil, being worn away and transported from its original site.

Transportation is where rivers move, sand, mud and rocks.

Deposition is when sand, mud and rocks are dropped by the river.

And a landform is a natural feature created by a process such as erosion or deposition.

We're going to be using these keywords throughout the lesson, and by the end, I know you are gonna be able to use them and understand them.

Our lesson today on river landforms and processes has two parts.

Our first part is, What processes happen in a river? And the second part is, What landforms can rivers create? So let's start the first part of the lesson.

What processes happen in a river? Let's go.

If you remember from our first lesson, we established that rivers are a constant flow of water across the land.

We established that rivers come in all shapes and sizes.

Some rivers are very large, and some are much smaller.

You can see a photograph of a river on your screen.

I'd like you to think about this question for me.

I want you to imagine, if we dropped a small grain of sand into a river, what might happen to it? I'd like you to think about this with your talk partner or geography buddy.

Pause the video and have a think, what might happen to a small grain of sand if we dropped it into a river? Off you go.

Wow, what amazing ideas you've had.

Oh, it's brilliant to see you really engaging with this question.

Some other children have had a think about this as well, and they've also come up with some ideas.

Let's see how close they were to ideas that you came up with.

So Lucas said the small grain of sand might sink.

Did you think that? Hmm.

Laura thought it might get moved along with the flow.

Hmm, interesting.

Is that something that you thought about in your discussion? And finally, Sam said it might scrape away at the sides of the river.

Ooh, interesting thinking, Sam.

I wonder if anyone else thought of that.

So, three different ideas there that we're going to investigate.

There are three main processes that happen in a river.

If you remember, Lucas suggested that material might sink.

He's absolutely right that that's a possibility, and this process is called deposition.

Deposition.

Laura's idea was that material might get moved along with the flow of the river, and that's a really good idea as well, and this is called transportation, so well done, Laura.

And finally, Sam suggested that material might scrape away at the sides of the river, and he's right as well, and this is called erosion.

So we have three processes, deposition, transportation, erosion, and all of these happen in a river.

Water that moves has energy, and it's the energy of the movement.

When we look at a river, we can see it flowing, can't we? Sometimes it flows very fast, sometimes it flows quite slowly.

I wonder if you have ever played Poohsticks and you've dropped a stick under a bridge and seen the way it comes out under the bridge, so we can see how rivers flow.

And this energy from the flow allows water to transport things like sand.

I've got a video that I'd like you to watch now to help illustrate this idea of transportation.

In this video, you're going to see a snow globe, a bit like the one in the picture.

A snow globe is a sphere which has water inside and also some material that looks like snow.

When you play the video, I want you to watch it really carefully and see what happens to the snow when we shake it.

Once you've watched the video, I'd like you to talk to the people next to you and discuss what you've noticed.

Okay, so play the video, and then have a discussion.

What do you notice happens when we shake the snow globe to the snow inside? Wasn't that video fascinating? It's so amazing, isn't it, when we see things really close up and we really think about it.

I wonder what you discussed when you watched the snow globe and saw what happened to the snow.

Andeep's been thinking about this, and he's noticed that, after it's shaken, the snow is transported around the globe.

Did you notice that as well? When it was shaken, initially, we can see the grains of snow.

They're caught up, aren't they? And they're moving around inside the globe.

They're being transported.

It's very like what happens in a river.

Because the water in rivers is moving, rocks, sand and mud can be transported with the flow.

So, just like the bits of snow in the snow globe were transported in the snow globe when it was shaken, so rivers, as they flow and move along, they can transport rocks, sand and mud with the flow.

They can do this in a variety of different ways.

For example, some material might float and be floating in the river, some material might bounce along the bottom and be moved that way by the river's flow, and some material might roll.

You've probably spotted, haven't you, that the heaviest material, big stones, will roll along the riverbed, whereas medium-sized materials might bounce along, and the lightest materials will float.

There's one other thing we haven't yet talked about.

Some substances, like, for example, salt, will dissolve in the water, and therefore they can't be seen as they float along.

So we can't see salt when it's dissolved, can we, into water, but it's still there, and so some substances are actually dissolved and transported along the river that way as well.

So I'd like us to check what we've learned so far about transportation in the river.

I'd like you to match the labels with the correct place on the diagram.

So can you find an example of floating in the diagram, can you find an example of rolling in the diagram, can you see an example of bouncing, and can you see an example of a material that's dissolved? Pause the video, see if you can match them in the correct places.

Fabulous geographical thinking.

I can see your brains are really switched on and your geography caps are in exactly the right place.

Yes, so, here we have some floating material, here we have some material, perhaps salt, that's been dissolved into the river and is carried along in the flow, transported along in the flow, here we have some heavy materials that are rolling along the river bed, and some less heavy materials that are bouncing.

Well done if you were able to correctly match those labels with the places in the diagram.

Brilliant thinking.

Now, faster, more powerful rivers can transport bigger rocks.

That makes sense, doesn't it? The larger the river, the more powerful the flow, and therefore, they're able to transport larger rocks.

And often, the largest rocks can get moved during a flood, because then we have an enormous volume of water in a river, and it's gonna be flowing really quickly.

I've got another video for you to watch now.

In this video, you're going to see a river.

I'd like you to look very, very carefully at this river and think about this question.

Will the river in the video transport large rocks? Think what we've just been saying about faster, more powerful rivers.

Watch the video carefully, use your geographical brains to assess the river, then after you've watched the video, talk to your talk partner about, will that river be able to transport large rocks? Off you go.

Well, I hope you enjoyed that video.

That was a beautiful river, wasn't it, in that wooded glade.

I'd quite like to be by that river myself.

Could that river transport large rocks? Well, Lucas doesn't think so.

He says, "This river looks too small to transport large rocks." I think I agree with him.

Do you? It was a really shallow river, wasn't it? Quite a small river.

I don't think that river could transport large rocks, so well done if you agree with him.

Let's move on a bit more.

So as the water slows down, it loses its energy, and that means it can't transport things any longer, so then material is deposited, which means that the material that's been carried along by the river is dropped.

Let's have a little bit more of a think about this idea, because it's quite complicated, isn't it? We're gonna return to the snow globe video that you looked at before.

This time, I'd like you to watch very carefully as the water in the snow globe slows down.

At the beginning of the video, the person shakes it, and all the material is being transported in the globe, isn't it? But as the water slows down, what happens to the material in the snow globe? Again, play the video, then talk to the person next to you and see what you think, and we'll share our ideas shortly.

Oh, wasn't that a great video? I don't know about you, but I just find snow globes really, really calming, actually.

What did you notice as the water in the snow globe slowed down? Well, Andeep's been doing a bit more thinking, and he says that when the water slows down, the water loses energy and the snow is deposited on the bottom.

Did you notice what Andeep noted? The snow was being transported, wasn't it? Gradually, as the water slowed down, it started to sink to the bottom, didn't it? And we call, in geography, that's called deposition.

The snow was being deposited on the bottom, and that's exactly what happens in a river.

As the river slows down, there's less energy, and the material that's being transported stops being carried by the river and begins to be deposited.

So when rivers slow down, they deposit sand, mud and rocks.

Look at this photograph here.

This river is a very wide river and quite a shallow river, so it's got a lot less energy than it might have had when it was closer to its source.

Can you see sand that has been deposited by this river? Pause the video.

Talk to the person next to you.

Where might we see some evidence that deposition is happening? Oh, brilliant thinking, geographers.

Yes, that sand is there because it was originally transported by the river when the river had lots of energy and was flowing really fast, but as the river is slowing down, it's losing energy, it's depositing that sand, and you can see it there.

Looks like a fantastic place to go and paddle, doesn't it? Here's a diagram that's gonna help us understand our third river process.

Sand, rocks and mud that are transported in the river will scrape away at the bottom and side of the river.

This causes erosion.

Material in the river will cause erosion as it flows along the course.

So, as a river is flowing, it's transporting material, particularly when it has lots of energy.

This material can scrape away at the bottom of the side of the river as it goes along, and this process of scraping away is called erosion.

Look at that river there.

I think we saw this river in our first lesson, didn't we? This is a big, powerful river.

I think I said last time, I wouldn't really want to canoe down this river, 'cause it looks a little bit scary.

Bigger, more powerful rivers erode more than smaller rivers.

I'd like you to think about why you think that is.

Let's really engage those geographical brains and think what we've been thinking about about flow and power and energy.

Pause the video.

Talk to the person next to you.

Why might bigger, more powerful rivers erode more than smaller rivers? Off you go.

Amazing thinking, geographers.

I can see you're really ticking over and using your geographical skills here.

Alex has thought about this as well.

He says, "Bigger rivers will transport more rocks and sand, which will scrape away at the river bed.

The force of the water will also cause erosion." Alex is right, isn't he? Imagine if you were standing on the bank, looking at that river.

Can you imagine what it would be like? It would be really noisy, wouldn't it? There'd probably be lots of spray soaking you if you stood too close.

This river is really flowing very, very quickly, and it's very powerful, and that energy is going to enable it to pick up quite big rocks and sand and pull them along, and as they move, they're going to scrape away at the river bed and cause erosion.

In a smaller river, there won't be that level of energy, and so there won't be as much erosion.

Now, this is a fascinating photograph.

As rivers have the power to erode the land, they can actually move across the land over time.

This is an aerial photograph and it shows where the river has been in the past.

If you look carefully, you can see there's a label saying Rio Negro.

That's the river now, the dark blue line of the river.

You can see I've labelled it the current river course.

Hmm.

Well, I wonder where the river might have been in the past.

Can you see anything in that photograph that shows possible evidence of where the river might have been? Good thinking.

Look, here are some scars where the river has been in the past, so we can see evidence there, can't we, that the river has moved across the land over time.

Isn't that extraordinary? Okay, I'd like you to try this practise task for me now.

So we're thinking about what processes happen in a river.

I'd like you to match the labels with the correct river.

We've got two rivers here, haven't we? The river at the top and the river at the bottom.

So, think, which of those has a slow flow of water? In which of those will the power of the river cause erosion? In which river will there not be much deposition as the water is fast? Which river can't transport much material? Which river can't erode the land very much? Which river can transport lots of material? And which river has a fast flow of water? I'd like you to work on this, thinking about what you've learned so far, and I look forward to seeing what you've done.

Good luck.

Fabulous thinking.

So, that river at the top has a slow flow of water, doesn't it? You can see that from the photograph.

There's not much deposition, because the water's quite fast.

It can't transport much material, can it, 'cause it's quite a shallow river, and it can't erode the land very much, because it's not really going very fast.

However, the river at the bottom can transport a lot of material, can't it, 'cause it's flowing really quickly.

There's a fast flow of water, and this river has enormous power, and it's going to cause erosion.

Well done if you managed to match those correctly.

So our second part of the lesson is this question: What landforms can rivers create? Let's go.

As we've established, rivers have enormous power, and that means they have the power to create incredible natural landforms. Look at this extraordinary photograph.

Again, imagine that you were standing on that cap of rock.

Can you imagine the noise of that river? Can you see the power of the river? You can see that the water's slightly brown, because lots of material is being transported in it because it's so powerful.

This is a waterfall, and happens by erosion when water falls over a cliff.

And you can see there, can't you, the cliff, you can see the water as it's flowing, falling down the cliff.

But how is this landform formed? Let's investigate in a bit more detail.

I've got a diagram for you here to help you understand.

So waterfalls are usually formed when a river flows from a hard rock to a soft rock.

On the diagram I've labelled the hard rock.

Here is the water, the river.

It's flowing along over the hard rock, when suddenly, it comes to an area of soft rock.

As it reaches the soft rock, it can erode that more, because it's softer, and that begins to create the waterfall.

The soft rock lying under the hard rock erodes more quickly.

This leaves a steep cliff for the water to flow over.

Over time, more and more erosion will happen, and the soft rock will be eroded away more and more, eventually creating the amazing waterfall feature that you saw in the previous photograph.

Okay, let's see if we understand how waterfalls are formed.

I've got a true or false question for you here.

Waterfalls can form when a river flows from an area of hard rock to an area of soft rock.

Is that true or false? Excellent, geographers.

It's true, isn't it? But why is it true? I'm going to give you two statements, and I'd like you to see which one you think makes sense.

Is it A, hard rock erodes faster than soft rock, so a cliff can form when the hard rock is eroded away, or is it B, soft rock erodes faster than hard rock, so a cliff can form when the soft rock is eroded away? Which of those makes sense? Pause the video.

Have a think.

Fantastic, geographers.

It's B, isn't it? It's the soft rock that erodes faster than hard rock, and as the river flows from the hard rock to the soft rock, it erodes away, forming a cliff, and eventually, that will form a waterfall.

Excellent if you got that correct.

Let's check this a different way round, so we really understand how waterfalls are formed.

Think about this question.

Where is the hard rock and where is the soft rock on this diagram? Pause the video.

Talk to the person next to you.

Fantastic, geographers.

Yes, the hard rock is at the top, isn't it? That's where the river's been flowing over.

It's then met an area of soft rock, which is softer, so it can erode more, and over time, it's formed a cliff and that's led to a waterfall.

Brilliant if you've got that right.

So waterfalls are not the only landforms that rivers can create.

Do you notice about the course of the river in the aerial photograph? And the course is the name that we give to the path a river takes on its journey to the sea.

It's an amazing photograph, isn't it? And you might have spotted that it's not straight, is it? In fact, Sam says it's not straight.

It has a very wiggly course.

It wiggles all over the place, doesn't it? What a wiggly river.

A bend like that in a river is called a meander.

I love that word.

I just love these geography words, and I love the word meander.

Rivers create lots of meanders over their course.

In that photograph, we could see that the river had meandered hugely over its course, hadn't it? Here's a diagram of a meander on your screen.

Let's just check what we understand by this word.

Can you finish this sentence for me? A meander is A, when a river flows over a cliff, B, when rocks roll along the river bed, or C, a bend in a river.

Pause the video and have a think.

Fantastic, geographers.

A meander is a bend in the river, isn't it? A, when a river flows over a cliff, that's a waterfall, isn't it? And B, when rocks roll along the riverbed, that's transportation, isn't it? Let's dig a bit deeper into this understanding of meanders.

Look at the diagram here.

The river water at meanders is deeper and faster flowing on the outside of the bend, you can see that on your diagram, and slower flowing on the inside bend.

Can you see in that diagram how we've got an area of deeper water, that's the outside of the bend, and some shallower water, that's the inside of the bend? Where it's deeper, we have a faster flow, which makes sense, doesn't it, because there's more water to flow faster, and where it's shallower, we have a slower flow, because there's less volume of water and less energy.

On the outside of the bend, we will have erosion, because the water is flowing faster, and so it will scrape away and erode.

The inside of the bend will have sand and mud deposited, because it's shallower and there's a slower flow.

So erosion on the outside, deposition on the inside of the bends.

Let's have a look at this diagram.

Here, you can see we've got the outside and the inside of the bend.

Where the river is deeper, you can see the cliff, which shows that there is erosion on the outside of the bend.

That's the top arrow.

In the second arrow, we can see that the shallower water, the lower flow, has led to deposition, and so we've got areas of sand and mud being deposited on the inside of the bend.

So erosion on the outside, deposition on the inside of the bend.

Let's just check our understanding here.

Let's look at this diagram again.

Where will the river be eroding the land on this diagram? Remember, eroding is scraping and wearing away.

Pause the video and have a think.

Excellent, geographers.

It's on the outside of the bend, isn't it? So there we've got the labels erosion.

Erosion happens on the outside of the bend, where the water is deeper and there's a faster flow.

Our third landform we're going to look at is a floodplain.

Look at the photograph here.

We can see the river, can't we, in the middle of the photograph.

Can you notice, on either side of the river, there are some flat areas? They are called floodplains.

You can see them labelled here.

They're called a floodplain, because this area might flood in times of heavy rain.

Maybe you've been having some heavy rain recently with you.

You might have noticed if you've been on a train or been out in a car that rivers can sometimes overflow their banks.

This area, the flat area, is the first area that's going to get flooded, and so we call it a floodplain.

I'd like you to label the floodplain and the meander on this photograph.

Pause the video and have a think.

Well done, geographers.

There's the floodplain, either side of the river, excellent, the area that can be flooded, and there's the meander, the bend in the river, where we'll have erosion and deposition taking place.

Fantastic if you got that right.

Our final landform is called an estuary.

Estuaries are created at the mouth of the river where it meets the sea.

You can see in the photograph, can't you? There's our river, and there's a bridge over the river.

We often have bridges over estuaries, 'cause they're important places for lots of reasons.

And out in the distance we can see the sea.

At an estuary, we have the fresh river water meeting the salty sea water, and they intermingle, and that area is called an estuary.

Let's just check our understanding of that landform, geographers.

An estuary is where A, a river turns a corner, B, fresh river water meets and mixes with salty sea water, C, a river flows over a cliff, or D, there's a flat area at the side of the river.

Which is it, geographers? Pause the video.

Have a think.

Amazing, geographers.

It's B, where fresh river water meets and mixes with salty sea water.

A was a meander, wasn't it, where a river turns a corner, C, yes, a waterfall, where a river flows over a cliff, and D, the flat area at the side of the river is the floodplain.

Okay, our final task today.

We've learnt a huge amount of geography words today connected with rivers.

I've got four photographs for you with four different landforms that we've been discussing in this lesson.

I'd like you to match the picture to our four words, estuary, waterfall, meanders and floodplain, and then I'd like you to write a sentence describing what they are.

Use the information that we have learned about in this lesson.

Good luck, geographers.

I'm really looking forward to seeing what you've written.

Wow, what a lot of hard work you've been doing.

I'm just so amazed at how quickly you're taking to this like a duck to water.

Okay, the photograph in the top left, that's the floodplain, isn't it? The flat area on the side of the river.

The bottom, we've got a waterfall, and that's where a river flows over a cliff, and it erodes away at that soft rock.

The top right is an estuary, and that's where fresh river water meets and mixes with salty sea water.

And finally, in the bottom right we have a meander, and those are bends on the river's course.

Well done if you managed to match those correctly.

You really are developing your understanding of rivers, geographers.

So let's summarise what we've learned today.

We've learned that rivers erode, transport and deposit material.

We've learned that bigger, more powerful rivers erode the land more quickly than smaller rivers.

We've learned that landforms like waterfalls, meanders and floodplains are created by rivers.

And finally, we've learned that an estuary forms where fresh river water mixes with salty sea water.

What a lot of amazing work we've learned about today in Rivers.

I'm really looking forward to our next lesson, where we're going to continue learning about rivers.

Until then, take care, and see you soon, geographers.