Hello and welcome to today's lesson.

My name is Mrs. Mehrin and I'm so excited to be learning all about weathering and erosion of rocks with you.

Let's begin.

Welcome to today's lesson from the unit Rocks and Soils.

Your lesson outcome today is, I can describe how natural forces can change rocks over time.

Now we are going to be touching on some of your previous learning all about rocks.

And I know that learning can be a little bit challenging sometimes, but that's okay because we are going to work really hard together and we are going to learn lots of fabulous new things.

So here are your keywords for today.

Now, you don't need to write these keywords down because I am going to be referring back to them throughout today's lesson.

However, if it makes it easier for you and you would like to write them down, you can pause the video now.

Off you go.

Fantastic.

Well done.

And here are all of the definitions for those five keywords.

Now again, I am going to refer to these definitions throughout today's video, so you don't need to pause it and write it down, but if it does help, you can do that now.

Off you go.

Fantastic.

Well done.

So there are three parts to today's lesson.

Let's begin with the first one, weathering of rocks.

Look at these different shaped rocks in the landscape.

Do you know why they are such interesting shapes? I'll give you five seconds to think about your answer.

Off you go.

Fantastic.

Well done.

So the strange shape of these rocks has been caused by something called weathering.

Now, weathering is the breaking down of rocks on Earth's surface, over time, by natural forces.

Now, before I tell you what natural forces are, do you think you could name any natural forces? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

So here are some examples of natural forces.

The wind, the rain, heat, and cold are all natural forces.

Now weathering is happening all around us every single day.

Can you spot the signs of weathering in these pictures? I'll give you five seconds to have a look at these pictures and come up with some answers.

However, if you need longer, you can just pause the video here and you can come back once you are ready.

Off you go.

Fantastic.

Well done.

So the roof and the walls of this house are starting to fall down and you can see that on the picture.

The detail on these statues is starting to disappear.

So if you look, for example, at their faces, you can see that they're not as defined as they might have been when they were first made.

And on the gravestone, you can see that the writing on the gravestone is being worn away.

Now let's do a quick check-in of your learning so far.

True or false? Weathering is a natural process.

Is that true or is that false? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is true.

Now let's see if you can justify your answer.

Is it because A, weathering is when humans change the shape of the land, or B, weathering is when rocks are broken down over time because they are exposed to heat, cold, rain, and wind? Again, I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

The answer is B.

Weathering is when rocks are broken down over time because they are exposed to heat, cold, rain, and wind.

Fantastic learning so far.

Well done.

Now let's do another question.

It says, which of these are examples of weathering? So have a broken eggshell, a castle ruin, or a damaged twig.

So again, I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is B, the castle ruin.

Now, we've got Sofia here and she says, I wonder how natural forces, such as wind, rain, heat, and cold, cause weathering to happen.

Do you know? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

So the wind has blown over thousands of years in this desert carrying small pieces of sand which act like sandpaper, wearing down the softer sandstone rock.

Now the harder rock underneath has been left behind to create this really strange shape.

Now, water seeps into permeable rock when it rains.

At night, and when it gets colder, the rain freezes and turns into ice, which expands inside the rock and pushes against it.

So during the day, the ice thaws, and over time, this freeze-thaw cycle causes cracks in the rock, eventually splitting the rock apart through weathering.

So it's another natural force.

Now weathering can also be caused by water seeping down through rocks and over time, washing away parts of permeable rock, creating caves and gaps in rocks.

So here, we have a limestone pavement.

In this cave, the rain has washed down through the limestone, creating stalactites which hang down from the roof of the cave, and stalagmites which have built up from the floor.

Animals and plants also play a part in weathering.

So animals that burrow and dig can wear away rocks and make holes in them to live in.

So for example, worms, or for example, a meerkat burrow.

Plants and their roots can split rock over time.

This is also a type of weathering.

So we've got roots in rock and shoots in pavements.

So next time you are outside, see if you can spot any of these, especially the shoots in the pavement.

Now, weathering of rocks occurs over time and can be caused by what? Is it A, earthquakes and volcanoes, B, wind and rain, C, heat and cold, or D, animals and plants? So I'll give you five seconds to think about which of those answers you think are correct, but if you need longer, you can pause the video here and you can come back once you are ready.

Off you go.

Fantastic.

Well done.

The answers are B, C, and D.

Now for your first task, it says, let's spot the signs of weathering around us.

So go for a walk outside in your local area with a camera or notepad and pencil.

And I want you to look carefully for signs of weathering.

So you might observe the buildings, the pavements, the walls, or the paths.

And I want you to make notes or take photos of rocks that show weathering.

Explain what type of weathering you think has affected the rock.

Do you think it's rain, wind, heat, animals, or plants? So you are going to have to pause the video here.

You're going to have to go and do the activity and then come back once you are done.

Off you go.

Fantastic.

Well done.

So, it says here, look carefully for signs of weathering in your local area, which is the task that you were doing, and to explain what type of weathering you think has affected the rock.

Was it the rain, the wind, the heat, animals, or plants? So here's one that someone has done and it says, these steps show signs of weathering because the rocks are jagged and worn away.

I think the rainfall and wind, over time, and humans using it has caused the weathering.

So here, this person's included more than just one example.

Here's another one.

It says, when I went to the park, I saw this tree.

Its roots were growing through the rock, making cracks in the rock.

I think the rocks were there before the tree grew so big and this is a type of weathering.

So you may have found similar things or you may have found something different, different signs of weathering.

Fantastic.

Well done.

So, now we are on to the second part of our learning today called erosion of rocks.

It says, look at these different rocky landscapes.

So we've got a cove, a river, and a valley.

Land has been worn away by natural forces, such as water or wind, and transported to another location.

This is called erosion.

So imagine you have built a sandcastle.

A wave comes in and takes some of the sand away from the castle back down the beach into the sea.

So here we've got the sandcastle, then the effect.

So the wave comes in, takes some of the sand away from the castle, back down the beach and into the sea.

Now the wave is the transport for the sand, moving it from one place to another, and we call this transportation or erosion of the sand.

So Laura asks, so weathering happens first, causing bigger rocks to break down into smaller pieces? And Alex says, yes! Then erosion is the process where these smaller bits of rock could get transported away to another place.

Lucas says, my wheelchair is my transportation, as it moves me from one place to another.

So let's do a check of your learning so far.

And it says, erosion is when sandcastles are destroyed, worms dig through the ground, or C, land is worn away by natural forces and is transported to another location? So again, I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is C, erosion is when land is worn away by natural forces and is transported to another location.

So, who do you think is correct? So we've got three people here.

We've got Andeep, Sam, and Izzy.

Andeep says, erosion and weathering are just different words for the same thing.

Izzy says, weathering breaks down the rocks and erosion transports the rocks.

And Sam says, erosion breaks down the rocks and weathering transports the rocks.

So who do you think is correct? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is Izzy.

Weathering breaks down the rocks and the erosion transports the rocks.

Now, fast running rivers create waterfalls and gorges as they transport the bits of rock away to the bottom of valleys creating sandbanks.

Now, erosion can also make sinkholes appear, which are when parts of land drop away to leave a big hole with rocks and sediment at the bottom of them.

Now erosion can be caused by the wind, especially in hot, dry places like deserts.

The wind picks up small bits of weathered sandstone rock and via transportation, moves it with the air to other places to create sand dunes and long, narrow rocks called yardangs.

Now here, we have a picture of a glacier.

So a glacier is a small moving, large area of thick ice that stays mostly frozen year after year.

As this ice moves across the land, it picks up pieces of weathered rock, and the ice acts as transportation for the rocks and carries them many miles over a long period of time.

Now over time, the ice begins to melt, creating glacial lakes, surrounded by piles of loose rocks that have been left behind.

So we can see that in the picture here on the right-hand side at the bottom.

Now let's do a quick check of your learning so far.

It says, which of these things can cause erosion? Can it be a worm, fire, or a glacier? I'll give you five seconds to think about your answer.

If you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answers are A, worm, and C, glacier.

Fantastic learning.

Now, Aisha has made a model of a glacier to show how they can cause erosion.

She froze a container of water in the freezer overnight to make a block of ice like a glacier.

Now she put on a thick glove so she could hold her glacier and put it into a tray of grass and small pebbles mixed together.

She pressed down hard on her glacier and pushed it across the tray.

Now, what do you think has happened to the sand and the pebbles fell underneath the ice? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

So as the glacier moved across the tray, it picked up bits of pebble and sand and transported them.

So we can see here that the glacier is travelling downhill and then transported sediment is pushed by the glacier, and then there is an erosion of hill and sediment that is left behind.

Now, this is the underneath of the glacier with the sediment embedded.

So as the ice began to melt, the sand and the pebbles dropped off into a pile.

Aisha's model shows how glacial erosion happens.

Now I want you to have a go at making a model to show how water can cause erosion.

So you're going to set up your equipment as is shown in this diagram here, and you're going to predict what you think will happen to the pebbles and gravel at the top of the riverbed, so this is the top of the drainpipe here, when the rain comes.

And I want you to draw a diagram to show what happened and write a sentence to explain.

Now, in that sentence to explain, I want you to include these keywords, erosion, water, transportation, and river.

So what you're going to do now is pause the video and have a go at that activity.

Off you go.

Fantastic.

Well done.

Now, it says here, when we added the water to the dry riverbed, which was the drainpipe, the water modelled transportation of the smaller pebbles and gravel as it flowed down.

Some of the gravel and pebbles were carried away and ended up making a bank in the bowl.

And this is water erosion.

Now, that takes us on to the third part of our learning today, which is the impact of weathering and erosion.

So weathering and erosion usually happens slowly over a very long time, but sometimes, in hot countries, the high temperature can cause natural disasters like droughts and hazards like heat waves which can speed up weathering and erosion.

Now, this can cause habitat loss.

As rocks crumble and plants die, their roots no longer hold the ground together and the wind blows sand and small rocks around.

Animals may find it hard to find food and shelter.

Now sometimes, due to extreme weather, erosion can happen very quickly in just a few hours, causing natural disasters.

So here we have a picture of a flooded river.

And we've got a picture here of the foundations of a house which have been eroded away.

Now if you have large amounts of rain, which fall really quickly, this can cause flood rivers and wash away riverbanks and the foundations of houses and buildings.

So if the foundations have been eroded away, that's going to make the house really unstable and could cause the house to collapse.

Now let's do a quick check-in of your learning.

It says, which of these natural disasters are caused by weathering and erosion of rock? Is it drought, landslide, or a wildfire? So think about the natural disasters which are causing the weathering and the erosion of rock.

I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is B, landslide, and A, drought.

So geologists and other scientists help to reduce the impact of weathering and erosion to people, animals, and habitats.

So they might do this by designing sea defences to protect houses from powerful waves, like the one in the picture here.

Advising the town planners where to put drains and flood barriers.

And suggesting erosion and weathering-resistant building materials like quartz.

Now, scientists like geologists and botanists can help by supporting farmers in hot countries.

They can advise how to stop land drying out in dry weather and recommend the best crops to grow.

Now, can you think of anywhere you may have seen the work of a geologist or scientist helping to protect people from natural disasters due to the impact of extreme weathering and erosion? So let's have a really good think.

Think about where you might have seen the work of geologists and scientists helping people and protecting them from natural disasters.

So I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

So we have got these three ideas.

So metal netting to stop rocks falling down the cliff onto the beach.

You might have seen that if you went down to the beach.

Houses that are being built on stilts to keep them above the flood water.

And deep drains next to the motorway to drain water away faster.

Now, true or false? We need help to eliminate the negative effects of weathering and erosion.

I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

The answer is true.

We do need help to eliminate the negative effects of weathering and erosion.

Now let's see if you can justify your answer.

Is it because A, the weathering and erosion doesn't cause negative effects, so we don't need help to eliminate them, or B, different types of scientists, including geologists, work to help eliminate the negative effects of weathering and erosion? So I'll give you five seconds again to think about your answer.

Off you go.

Fantastic.

Well done.

The answer is B.

Now, which of these could help reduce the impact of weathering and erosion of rock on habitat loss and natural disasters? So is it A, clearing farmers' field of trees and bushes, B, building houses further away from the sea edge, or is it C, using impermeable rocks like quartz and granite to build with? So again, I'll give you five seconds to think about your answer, but if you need longer, you can pause video here.

Off you go.

Fabulous.

Well done.

The answer is B and C.

Now here is your final task for today's lesson.

It says, imagine you are a scientist who wants to help reduce the impact of natural disasters.

Discuss with a partner what you could do to help prevent extreme weathering and erosion.

So you might suggest an idea to prevent damage from extreme heat, rain, wind, animals, and plants or the sea.

So, I'd like you to pause the video here and have a go at that activity.

Off you go.

Fabulous.

Well done.

So here, these are some of the ideas that you might have suggested.

So putting up windbreaks.

So it says, I would put windbreaks up to prevent sand dunes from being blown into the sea.

I would advise planners to build houses on platforms from impermeable rock next to rivers that might flood often.

Or I would encourage farmers to grow crops that don't need much water in hot countries, so animals have shade and food.

Now we are onto the summary of your learning.

It says weathering is the breaking down of rocks on Earth's surface, over time, by natural forces.

Erosion is when land is worn away by natural forces, such as water or wind, and transported to another location.

Weathering and erosion of rock can cause habitat loss and natural disasters.

Different types of scientists, including geologists, work to eliminate the negative effects of weathering and erosion.

Now, you have worked so, so hard.

There's been lots of new information to learn and some of it's quite tricky as well.

But you have worked magnificently.

I am so proud of you.

Well done.