Lesson video

Hello, my name is Mrs. Grey, and I'm so excited that you've decided to join me for today's geography lesson.

Today's lesson is in our unit of "Ice and glaciers: How are cold places affected by a warming planet?" And today's lesson is called "Glacier Formation." By the end of the lesson, you will be able to explain what glaciers are, how they form, and why they move.

There are some key words that will come across in today's lesson.

They are cryosphere, glacier, and gravity.

Now, cryosphere is the frozen parts of our planet.

A glacier is a huge accumulation of ice and snow that moves slowly overland down slope under the force of gravity.

And gravity is the force by which a planet, or other large body draws objects to its centre.

Now, today's lesson on glacier formation is split into two learning cycles.

The first learning cycle is what are glaciers? And the second learning cycle is how do glaciers form and move? So let's take a look at our first learning cycle now then, what are glaciers? So the frozen parts of our planet are collectively known as the cryosphere.

That's one of our key words there, isn't it? The cryosphere, the frozen parts of our planet.

And the cryosphere encompasses many different parts of our planet that are frozen.

Let's have a look at what they are.

So one of them is glaciers, and that's another key word from today's lesson.

Now glaciers are rivers of ice found in mountainous areas, or can be at the edges of ice sheets.

And that's one part of the cryosphere.

Another part of the cryosphere, the frozen parts of our planet are ice caps.

Now, ice caps, they are smaller masses of ice.

Another part of the cryosphere, that's ice sheets.

Now, ice sheets, they are really, really large masses of ice and they cover areas that are 50,000 square kilometres or more.

So really, really, really large masses of ice.

And then another area that's covered under the cryosphere is permafrost, and permafrost is frozen ground.

So the cryosphere, that frozen parts of our planet that encompasses all these different things, glaciers, ice caps, ice sheets, and permafrost.

So our first check of the lesson at then, which of the following best describes the cryosphere? Is it A, the frozen parts of Earth's surface? Is it B, the liquid parts of Earth's surface? Or C, the lower part of the Earth's atmosphere? What do you think? So pause the video, write down your answer and then come back and let's see how you got on.

Okay, how did you get on? Which of the following best describes the cryosphere? The answer is A, the frozen parts of Earth's surface.

Did you get that right? Well done.

So glaciers are slow-moving rivers of ice and snow that move slowly over the land, down slope, under the force of gravity.

Can you see that image there? Really, really big.

And they move really slowly, but they're like rivers of ice and snow moving.

They form in very cold regions of our planet where snow accumulates each year in the winter and doesn't fully melt in the summer.

So in the really cold parts where we get lots and lots of snow in the winter, but then in the summer, not all of that snow goes, so it accumulates and more and more of it comes each year.

Now glaciers cover about 10% of earth's land area today.

If you have a look at the map there, you can see that those darker blue areas that's showing where glaciers cover.

Now most glaciers are found in the polar regions, which is what you'd probably expect, but they can also be found in mountain ranges globally.

So if you have a look at that map, you can see the areas, you can see the areas in the Arctic and Antarctica.

And you can also see in other parts of the world, these are the mountain ranges that have also got glaciers in them.

So 10% of the earth's land that it covers altogether.

Now the Mer de Glace is a valley glacier in the French Alps, close to the border with Italy.

It's a really, really famous glacier.

And you can see on the map there where the Mer de Glace is.

It's the longest glacier in France and scientists study it to see how glaciers are changing over time.

And you can see that image there, that's a picture of the Mer de Glace in France.

Okay, another check then.

What percentage of land did glaciers cover? Is it A, 1%? B, 10%? C, 25%, or D 32%? So pause the video for a second, write down your answer and then let's see how you got on.

Okay, how did you get on? What percentage of land did glaciers cover? It's 10%.

Did you remember that? Did you get that right? Well done.

So the Lake District, that's a national park in northwest England.

Now its landscape was shaped by glaciers during the last ice age.

And although the ice is now gone, the area of the Lake District is really well-known for its stunning valleys and deep lakes, and they've been created by the movement of ancient glaciers.

It's a really, really famous landscape.

So you can see now what that landscape looks like.

Can you see that beautiful image there? And there's an arrow pointing to where it is on the map in the northwest of England.

So we're onto our first task of the lesson now then.

Question 1A, define the key word glacier.

And then 1B, on the map, label an example of a glacier in France and a glacier landscape in the UK.

So define the keyword glacier, what does glacier mean? And then on that map, you've got to label two examples.

One of a glacier in France and another one at a glacier landscape in the UK.

Okay, so pause the video, write down your answer and then come back and let's see how you got on.

Okay, how did you get on? So define the key word glacier.

So a glacier is a huge accumulation of ice and snow that moves slowly over land and down slope under the force of gravity.

And then the second one was on the map label an example of a glacier in France and a glacier landscape in the UK.

And can you see what they've labelled on here? We've labelled the Mer de Glace in the French Alps and the Lake District in the UK.

They're the two examples that we looked at.

Did you get them right? Well done.

So we're moving on to our second learning cycle of the lesson now, which is how do glaciers form and move? So glaciers forming regions where snowfall exceeds snowmelt year after year.

That means that more snowfalls than melts.

So we've got snowfalling, but not all of it melts.

And so it's able to build up year after year.

So fresh snow is light and fluffy with lots of air.

Now as more snow falls, the weight of that snow compresses the lower layers.

So they then have less air in them.

All the time, the snow compacts further and forms firn, which is a dense, grainy ice and fern eventually becomes glacier ice.

This is dense, hard and can appear blue since air bubbles are squeezed out.

So is this showing the formation of glaciers, how snow that forms which is really fresh and light and fluffy, how that eventually turns into dense, hard ice that we find in glaciers because as more and more snow falls that compresses those lower layers and there's less and less air in it, so it becomes less light and fluffy and are more dense and hard.

And that's how we get snow turning into glacial ice.

So snow's got about 90% air in it.

Then as we get to the next level, the coarse-grained snow has about 50% air in.

Then when it turns into firn, that's got 20 to 30% air.

And when we get to glacial ice, that's only got 20% of air in it.

So it's a big, big difference from snow, which is 90% air down to glacial ice, which is only 20% air.

And that's the big difference.

It's because of its compression.

It gets rid of that air and so it becomes thicker and harder and more dense, and that turns from snow into ice.

Now this process of forming a glacier can take centuries turning soft snow into solid ice, years and years and years, hundreds of years.

It takes a very long time.

Now the formation of the Mer de Glace glacier, can you remember where that is? In France, that image shows the Mer de Glace that took thousands of years snow accumulated in the high mountains of the French Alps and over thousands and thousands of years, that's then compressed into the Mer de Glace glacier.

So it takes a very, very long time.

So another check then, fill in the gaps below.

So glaciers form in regions where, what, exceeds snow melt year after year.

Layers of snow build up and the, something, compresses the lower layers into dense, hard ice.

And this process can take, what, turning soft snow into solid ice.

So we've got three sentences there and three gaps.

And you need to look at those gaps, read those sentences and fill in the gaps.

So pause the video, write down your answer and then come back and let's see how you got on.

Okay, how did you get on? So glaciers forming regions where snowfall exceeds snowmelt year after year.

Layers of snow build up and the weight compresses the lower layers into dense, hard ice.

And this process can take centuries, turning soft snow into solid ice.

Did you get those three words? Well done.

So glaciers are like frozen rivers.

These huge masses of ice move downhill very slowly as a result of the influence of gravity.

And you see that image there, that huge frozen river moving downhill because of gravity.

Now along with gravity, other processes are at work that result in glaciers moving.

Meltwater collects at the base of glaciers.

So underneath glaciers, we get something called meltwater.

This thin layer of meltwater acts as a lubricant and allows the glacier to slide downhill more easily.

So it's not just gravity that's pulling the glacier down, but the meltwater is acting as a lubricant so it's able to slip and slide downhill even easier.

Now, meltwater collect beneath the ice as a result of pressure, the earth's heat and something called percolation.

Now, pressure, that's the weight of the ice, means that melting takes place at lower temperatures at the base of the glacier.

So in actual fact, melting happens underneath the glacier because of a lot of pressure.

Now, the earth's heat also a factor.

Geothermal heat from the ground also melts the ice at the base of the glacier.

And percolation, summer meltwater at the glacier surface, percolates through the ice and drains to the base.

So these three different things cause meltwater to collect under that glacier, and that then helps it to slip and slide downhill even more.

So this GIF shows the Baltoro Glacier in Pakistan flowing from 1991 to 2002.

And can you see how it's flowing and moving over time? And you can see the arrow there points to whereabouts that is in the world.

Look at how it moves.

Now glaciers usually moves slowly at around 25 centimetres per day.

So that's less than like one of those big rulers, 25 centimetres, so think of a 30-centimeter ruler, 25 centimetres, it's just a little bit less than that.

So almost a big ruler on average per day.

And then they're sometimes surge faster than normal.

The Sermeq Kujalleq glacier in Greenland is one of the fastest on earth flowing at around 20 metres per day, and that's an image of that glacier there and showing you where it is in the world in Greenland, 20 metres per day.

So another check now then, which of these statements are true? Is it A, glaciers move slowly, B, glaciers move quickly, C, glaciers move at around 25 centimetres per day, and D glaciers move at around 25 centimetres per year? Which of those do you think is true? So pause the video for a moment, write down your answer and then come back and let's see how you got on.

Okay, how did you get on? Which of these statements are true? And the answers are A and C.

Glaciers move slowly and glaciers move at around 25 centimetres per day.

Did you get them right? Well done.

Okay, so now we're on to our second task of the lesson.

So question one, annotate the diagram to explain how snow turns into glacier ice.

So can you see that diagram there, which shows snow and how much percentage of air it's got in it? Then we move to coarse-grained snow, firn and glacial ice.

So you need to annotate that explaining how it turns from snow at the top all the way into glacier ice at the bottom.

Your second question is, how do glaciers move downhill? So you need to write a little bit of information to explain how glaciers move downhill, okay? So pause the video, write down your answer and then come back and let's see how you got on.

Okay, how did you get on? So the first thing you were to do was to annotate the diagram to explain how snow turns into glacier ice.

So the first little bit at the top, snow, which is 90% ice, you could have written, fresh snow, is light and fluffy with lots of air.

Now the next level down, coarse-grained snow, which is 50% air.

You may have written, as more snow falls, the weight compresses those lower layers so they have less air.

The next layer, firn, which is 20 to 30% air.

You might have written, over time, the snow compacts further and forms firn, a dense, grainy ice.

And then finally, the last one at the bottom, glacial ice, which is 20% air bubbles you might have written, firn eventually becomes glacier ice, which is dense, hard and can appear blue due to the lack of air bubbles.

Did you get all of those steps? Well done.

So question two is, what helps glaciers move downhill? And this is what you may have written.

Glaciers move because of gravity and their own weight.

A thin layer of water called meltwater forms at the base of the glacier.

It acts as a lubricant and this helps the glacier to slide downhill.

And there's a little image there as well to help explain.

You may have drawn a little image to help you explain.

So showing gravity moving and showing that little bit of meltwater as well, which can cause the glacier to move downhill.

Did you get both of those? Well done.

Okay, so we're at the end of our lesson now on glacier formation.

And what have we learned in today's lesson? So we've learned that the frozen parts of our planet are collectively known as the cryosphere.

Glaciers are large, slow-moving rivers of ice.

Glaciers are made up of snow and ice that has been compressed over many, many years.

And glaciers move under the force of gravity.

I've really enjoyed today's lesson on glacier formation and I hope you have too.

I look forward to seeing you next time.