Lesson video

Hello, my name is Mrs. Grey.

And I'm so excited that you've decided to learn geography with me today.

Today's lesson is in our unit of Ice and Glaciers.

How are cold places affected by a warming planet? And the lesson title is "Ice Change Over Time." By the end of the lesson, you will be able to describe the way that global climate has changed over time, and the extent of the British-Irish ice sheet.

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

They are climate, ice sheet and ice age.

Climate is an average of weather conditions, such as rain, sun, and wind in a place, taken over a long period of time, usually 30 years or more.

An ice sheet is a large mass of ice covering an area of over 50,000 square kilometres.

And ice age is a period of time during which thick ice sheets cover vast areas of land.

Today's lesson is split into two learning cycles.

The first, how has Earth's temperature changed over time? And the second, what was the British-Irish ice sheet? So let's have a little look at that first learning cycle, how has Earth's temperature changed over time? Earth's climate has varied over time.

The planet has experienced periods of global warming, and global cooling.

Warmer periods of time are called interglacial periods.

And cooler periods of time are called glacial periods.

Now you can see this graph here shows a very long period of time, and shows temperature changing.

And those warmer periods are called interglacials.

And the colder periods, the cooler periods, are called glacial periods.

And you can see those highlighted on the graph there.

Now this graph shows how the global average temperature has changed over the last 425,000 years.

That's a huge amount of time, isn't it? Now you can see that when the line goes up, that's showing that the Earth's average temperature is increasing.

And when the line is going down, that shows that the Earth's average temperature is decreasing.

So if you have a little look at that graph, you can see that the line goes up and down.

It's fluctuating, it's changing over the last 425,000 years.

And you can see the periods of time where the graph is going up, where the line is going up, and that's showing an increase in temperature.

And times when the line is going down, and that is showing a decrease in temperature.

Now, the term global warming, that refers to periods when Earth's average temperature rises.

So when the Earth's temperature rises and is going up, that's called global warming, because the globe is getting warmer.

Now, over the last 400,000 years, Earth has experienced a number of periods of global warming.

If you have a little look at that graph, you can see numerous times where that line is going up, where the globe is getting warmer.

And you can see that all of those periods on that graph are called interglacial periods, where the globe is warmer, and that's referred to global warming, and they are interglacial periods of the globe being warmer.

Now, global warming can lead to melting ice caps, shrinking or retreating glaciers, and rising sea levels.

So lots of different things can happen as a result of the Earth getting warmer, the globe getting warmer.

So that makes sense, doesn't it? That ice is gonna melt, that glaciers are gonna shrink, get smaller or retreat, move backwards, and that sea levels are going to rise because the ice is melting, and so there's gonna be more water in the sea, and the sea levels are rising.

So they're all the consequences, they're all the things that happen as a result of the Earth getting warmer, of global warming.

Now, global cooling, that's the opposite of global warming.

That refers to periods when the Earth's average temperature drops.

So when the temperature of the Earth goes down.

So over the last 400,000 years, Earth has experienced a number of periods of global cooling as well.

So can you identify them on that map? Can you see the times where the average temperature of the Earth has gone down? Can you see them all highlighted there? And they're called glacial periods.

Now, global cooling can cause glaciers to grow in size, or advance.

So that's gonna make sense as well, isn't it? If it's cooler, then those glaciers are gonna get bigger, or advance.

Okay, so our first check of the lesson then.

How has Earth's temperature changed over time? That's what we're looking at.

So the question is, "What does the term global warming mean?" Is it A, a period when Earth's average temperature rises? Is it B, a time when there are more rainstorms worldwide? Is it C, a time when Earth's average temperature stays the same? Or is it D, a period when Earth's average temperature drops? What do you think? So have a little look at that question again, 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? What does the term global warming mean? And the answer is A, a period when Earth's average temperature rises.

Well done.

Okay, so here's another, that graph again that we've seen, that graph, and then another graph on this slide.

The Earth is currently in a time period called the Holocene.

Now the Holocene is the very end of that graph, at the top that we've seen before.

And the graph at the bottom shows the Holocene in a little bit more detail.

Now, the Holocene began 11,700 years ago.

So it's a period of time, and that's the period of time that we are currently in.

And it began 11,700 years ago.

So during the Holocene, there have been warm and cold periods of time.

So let's have a little look at that graph again, that graph showing the Holocene, in a little bit more detail.

So the red line that goes all the way along, that indicates global average temperature over the last 11,700 years.

So the average temperature of the globe over the last 11,700 years, so the period of time called the Holocene.

Now those red areas where it goes, the line goes above the red line, that shows warm periods.

What do you think the blue areas are showing? They show cold periods.

Yeah, they've gone below the average temperature, and they show the colder periods of time.

So there was a particular cold period from 1300 to 1850 AD.

So that's around 750 years ago.

There was a particular cold period.

And this particular period was called the Little Ice Age.

And it affected the Northern hemisphere.

So the part of the globe that's up north of the equator, it affected that part of the Earth.

Now, during the Little Ice Age, there were three even colder periods, with really harsh winters and frozen rivers in Europe.

Now there was a warm period in the Holocene from 950 to 1250 AD.

And that was called the Mediaeval Warm Period.

And that also affected the Northern hemisphere.

So the part of the globe that's north of the equator, that's the area that it affected.

During this time, the average temperature was warmer in Europe, in particular.

Now the period of time that we live in, which is highlighted on the graph now, if you have a look, is also warmer than average.

So we're living in a period of time, period that's warmer than average.

Now during this period, this period of time that we're living in, there's been a significant rise in the average global temperature.

This temperature rise been most noticeable since the late 20th century.

So here's another little graph that we can look at.

This shows global surface temperatures.

Now there's three lines on this graph.

And this is because it's showing different data collected by different organisations in different parts of the world.

And the graph represents temperature change over almost 150 years.

So this is really, really recent.

Earth's temperature has risen every decade since 1880.

So every 10 years since 1880, the temperature of the Earth has risen.

The rate of warming since 1982 has tripled.

So the temperature of the globe is getting much, much warmer than it was.

It's increasing over time, and you can see that very clearly on that graph, can't you? So another little check for us then.

True or false? The Mediaeval Warm Period was a colder time with harsh winters and frozen rivers in Europe.

Is that true or false? 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? True or false? The Mediaeval Warm Period was a colder time with harsh winters and frozen rivers in Europe.

That's false.

But why is it false? The Mediaeval Warm Period was a warmer time, where there were warmer average temperatures in Europe.

Did you get that? Well done.

Okay, so now we're onto our first task of the lesson.

So question one.

On the graph, label an interglacial period, and a glacial period.

So you've got a graph there, and you need to label an interglacial period, and a glacial period.

Now there is more than one of each.

You just need to label one interglacial period, and one glacial period.

Or you can label them all if you want.

Question two, the graph shows the time period that Earth is currently in, which began 11,700 years ago.

So 2a is, what is the time period shown called? And 2b, on the graph, label the Mediaeval Warm Period and the Little Ice Age.

Okay? So you answer those two questions.

Pause the video, write down your answers, and then come back and let's see how you got on.

Okay, how did you get on? So on the graph, label an interglacial period, and a glacial period.

So you can see the answers there on the screen.

So if you labelled something above the red line as an interglacial period, then that was correct.

And below the red line, if you labelled an area as a glacial period, then that was correct.

Well done.

So this graph shows the time period that Earth is currently in, which began 11,700 years ago.

What is the time period shown called? It is called the Holocene.

And then on the graph, you had to label the Mediaeval Warm Period, and the Little Ice Age.

And if you can see there, it's labelled.

So the Mediaeval Warm Period is that little red bit, 950 to 1250 AD.

And the Little Ice Age is the blue bit, 1300 to 1850 AD.

Did you get those right? Well done.

Okay, so now we're onto our second learning cycle, which is what was the British-Irish ice sheet? So an ice sheet is a large mass of ice covering over 50,000 square kilometres.

They form in very cold places, where snow builds up, and doesn't fully melt.

Over time, the weight of the snow compresses the lower layers together into ice.

So the weight of the snow on top compresses the lower layers and then that turns into ice.

And this image that you can see on here, this is the Antarctic ice sheet.

Now the only current ice sheets on the globe, right now, are the Greenland ice sheet, which is in the Northern hemisphere, above the equator, north of the equator.

And the Antarctic ice sheet, which is in the Southern hemisphere, so south of the equator.

Can you see those highlighted on the map there? So another check then.

What is an ice sheet? Is it A, a thin layer of ice covering a small area? Is it B, a large mass of ice covering over 50,000 square kilometres? Is it C, a thick layer of snow that melts every summer? Or is it D, a small glacier found in mountain ranges? 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? What is an ice sheet? And the answer is B, a large mass of ice covering 50,000 square kilometres.

Well done.

So here's this graph again that we've seen before.

The last ice age ended around 11,700 years ago.

And that 11,700 years ago was the start of the Holocene, if you remember, from the last learning cycle, that's when the last ice age ended.

During the coldest periods of the last ice age, so 26,000 to 20,000 years ago, the global climate was cold enough for ice to form into glaciers and ice sheets.

And huge ice sheets covered large parts of the Northern hemisphere, so the part of the globe that's above the equator, that's north of the equator, had huge ice sheets covering it.

Now during the last Ice Age, around 22,000 years ago, the British-Irish ice sheet covered the north of England, most of Scotland, Wales, and Ireland.

And you see that image there that shows the UK and Ireland and it shows the ice sheets that's covering over it.

So much water was locked up as ice that the coastline was very different to its location around Britain and Ireland today.

In the west, the coastline retreated more than 150 kilometres.

So you have a look at, another look at that image there, you can see that all of that area of land was completely covered in ice.

So which parts of the UK and Ireland were covered by ice? If you have a look at the map, which areas can you locate? Some areas that were covered by ice? Scotland, Northern England, Ireland, and Wales.

South of the ice sheet, the conditions were still very, very cold.

So even though it wasn't covered in ice, it was still very, very cold.

The soil was frozen all year round, just as it is in tundra regions of the world today.

So very, very different conditions to what we live in today.

As temperatures warmed, the ice began to retreat.

So as the big ice sheet melted, it broke into smaller ice caps on higher ground.

So this big, big, big ice sheet, as it starts to melt, it broke up and we ended up with smaller ice caps that were still there on some of the higher up ground.

19,000 years ago, it was melting quickly.

17,000 years ago, the parts of the ice sheet over the sea were gone, and most of the ice had moved back to land.

And 16,000 years ago, the ice in Scotland and Ireland had split into two separate sheets.

Okay, so we're onto our second task of the lesson then.

Question one, match the term with the correct description.

So there are three key terms there, and there are three descriptions, and you need to match the term up with its correct description.

So the terms are ice sheet, British-Irish ice sheet, and last Ice Age.

And the descriptions are, a region covered by a massive sheet of ice during the ice age.

A time when much of Earth was colder, ending 11,700 years ago.

And a large mass of ice, covering over 50,000 square kilometres.

So you need to match those terms and descriptions.

Question two, shade the map to show the areas covered by the British-Irish ice sheet.

So you've got a map there and you need to colour over the areas that were covered by the British-Irish ice sheet.

Okay, so you answer those questions, pause the video, answer them, and then come back, and let's see how you got on.

Okay, let's see how you got on.

So match the term with the correct description.

So an ice sheet is a large mass of ice, covering over 50,000 square kilometres.

The British-Irish ice sheet is a region covered by a massive sheet of ice during the last ice age.

And the last ice age is a time when much of Earth was colder, ending 11,700 years ago.

Did you get all of those? Well done.

And then question two was shade the map to show the areas covered by the British-Irish ice sheet.

And if you have a little look on the screen there, you can see what your answer might look like, if you've covered over the areas and coloured the areas that were covered by the ice sheet.

Did you get it? Well done.

Okay, so let's summarise what have we learned today then.

Over the past 400,000 years, Earth has experienced periods of global warming and global cooling.

During periods of global cooling, or glacials, gigantic ice sheets formed in colder regions of the world.

At the height of the last ice age 20,000 years ago, much of the British Isles was covered by ice, known as the British-Irish ice sheet.

And the last ice age ended around 11,700 years ago.

Thank you for joining me for today's geography lesson.

I hope you've enjoyed it.

See you next time.