Lesson video

Hi everyone, my name is Miss Dhillon, and last lesson we were learning about what landforms rivers can create.

Can you remember how a V-shaped Valley is created? Is it through lateral or sideways erosion, or is it through vertical which is downwards erosion? Have a moment to think.

Well done, if you said vertical erosion.

So vertical erosion is downwards erosion, and that's how it V-shaped valley is created.

In the lesson today, we will continue to explore the question, what landforms do rivers create? This is what the structure of the lesson today is going to look like.

We will start by going through the star words, then we will be looking at the following.

First, we will study a satellite image.

Then, you will learn about meanders and how they form.

Next, we will learn about erosion and deposition and the role they play in forming a meander.

Then we will look at how an oxbow lake is created.

And finally, you will finish with a writing task.

But first of all, let's make sure we're ready for the lesson, so please make sure you have all the things mentioned on the screen.

On the screen, you can see the star words for today's lesson.

I will be explaining these star words in more detail throughout the lesson.

But first, let's start by saying them out loud using my turn your turn, meander, lateral erosion, middle course, deposition, sediment, oxbow lake.

Fantastic.

On the screen, you can see a satellite image of the Amazon River.

I want to know, what does this satellite image reveal about the Amazon River? How does it flow? Does it flow in a straight line? I wonder.

So have a few moments to look at the image and I'm going to give you a few moments to think about what this satellite image is telling us about the Amazon River.

Okay, did you notice that the river is bending and curving? Well done, if you did.

We can say that the Amazon River meanders.

Meanders means it curves and bends.

What does meander mean? Good, that it curves and bends.

We are now going to learn about how meanders form.

In the middle course, which is further away from the source of the river, rivers have more energy and therefore they do more erosion.

This erosion is more lateral, which is sideways erosion and this makes the river wider.

As the river erodes laterally it forms big bends in the river.

We call this a meander.

What do we call this bend? Good job, a meander, good listening.

Meanders form because of lateral erosion.

Show me with your hands what is lateral erosion? Good job, you should be saying sideways not downwards, that's vertical erosion.

So just be careful.

So meanders form because of lateral erosion and deposition, which is the dropping off materials.

I would now like you to pause the video to complete the task on the screen.

Here is the answer.

Did you get the answer correct? High five.

Well done.

You've made a great start to today's lesson.

Now I'm going to use an example of a car to explain the movement of the water around a bend.

When a car goes around a bend the speed is greatest on the outside of the bend, where is the speed greatest? Good job, on the outside of the bend.

The faster the car goes around the bend the more the driver and the passengers will be pushed to the outside of the bend.

Now, rivers work in a very similar way.

When the water goes round a bend the water on the outside of the bend has the most energy to erode on the outside of the bend.

Where does the water have more energy in the bend? Good job, on the outside of the bend, just like that fast car going around the bend.

Where you can see the arrow on the outside of the bend this is where the water is travelling the fastest and where the most erosion happens in a meander.

Pause the video now to complete the task on the screen.

Make sure you choose the correct word to finish the sentence.

Here are the answers.

Take a few moments to check your answers.

How did you do this time? I know you're paying close attention and trying your best, so keep up the good work.

As the water travels the fastest on the inside or outside of the bend, remind me? Outside of the bend, well done.

This means that the outside of the bend is continually being eroded, means it keeps getting eroded more and more.

And what this means is that the bend gets bigger.

You can see this in the diagram if you look closely at B.

In A, you can see that the river is starting to erode the sides, where is B, the bend is continually being eroded and that's what's making the bend bigger and bigger.

Water on the inside of the bend moves much more slowly.

This is where the river has less energy because it's moving more slowly.

What does it have? Good job, it has less energy and that's why it's moving more slowly.

So this is where most of the deposition occurs as the river has not got the energy to carry the materials.

So to summarise, when water goes around a bend, the water on the outside of the bend moves up? Fastest, well done.

And this means that the river has more or less energy? Good, it has more energy when it's moving fast and therefore, this leads to more erosion because it can break down the rocks, because it has more energy.

The outside of the bend is continuously being eroded, and this is what makes the bend, bigger, good job team.

So now we have learned about meanders and how they are formed.

Pause the video now to complete the task on the screen.

Make sure you choose the correct words to finish off the sentences.

Here are the answers.

Take a few moments to check your answers.

How did you do team? Well done, if you've got most, if not all of those correct.

Thumbs-up for you.

Okay, so now I would like to give you some thinking time, and the question I would like you to think about is this.

What might happen eventually, as the meanders get bigger and bigger, becoming increasingly close together? So this question I would like you to predict what you think will happen.

Your answer is not right or wrong is just a prediction, and then we will go through it together.

So take a few moments, pause the video, and think about this question.

As the meanders get bigger, the neck of the meander becomes more narrower.

You can see this as marked as a red cross on the image.

When the neck of the meander is very narrow, it is much easier for the river to break through when it gains more energy.

You can see this as the arrows in the image.

When the river cuts through the neck it forms a new path and leaves behind an oxbow lake.

You can see an example of oxbow lake in the image.

The oxbow lake is sealed off by sediment that the river deposits or drops off.

Is now time for your writing task.

You are going to explain how an oxbow lake forms. You have been given some sentence starters and keywords to help you.

Pause the video now to complete this task.

Here are the answers.

The keywords that have been used are in bold, so you can see how you can use them in your answer.

Spend a few moments reading this model example, and seeing how it compares to your own answer.

Okay team, so that is now the end of today's lesson.

And I hope you enjoyed this lesson as much as I did and lots and lots of new facts, about how landforms are created.

You should now feel more confident explaining what erosion and deposition is and where it happens in rivers.

Next lesson, we will be learning more about why rivers are important to people.

Bye everyone.

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