Lesson video

Hello, geographers.

My name's Mrs. Omigo.

I'm really looking forward to teaching you today.

I hope you're going to enjoy the lesson and learn lots.

Let's get started.

In today's lesson, we're going to look at an example of an upland glaciated landscape, and our example is North Wales.

So by the end of the lesson you will understand the landforms of glacial erosion and deposition that can be found in North Wales.

There are four keywords for today's lesson.

Last Glacial Maximum, known sometimes as the LGM on the slides, GIS, corrie or cwm, and contour lines.

So the Last Glacial Maximum is the period when ice sheets were at their largest extent during the last ice age, which was about 26,000 years ago.

GIS stands for geographic information systems, which are computer systems used for capturing, storing, analysing, and displaying geographic data.

A corrie, cwm, is a bowl-shaped hollow eroded by a glacier.

It's typically forming at the head of a valley.

And contour lines which are lines drawn on maps that connect points of equal height above sea level.

There are two learning cycles for today's lesson.

We're first going to locate a glaciated landscape in the UK and then secondly we're going to use maps and GIS to identify glacial landforms. Let's get started on our first learning cycle.

North Wales is a post-glacial landscape in the UK and it's part of Eryri National Park, Snowdonia.

There are no longer glaciers in North Wales, but we sometimes refer to it as a glaciated landscape due to the glacial landforms that were created in the past.

And we can see it there located on the map of the UK in the north of Wales.

Eryri is located in the northwestern part of Wales and it includes the highest peak in Wales, Yr Wyddfa, Mount Snowdon.

During the Last Glacial Maximum, North Wales was covered by the British-Irish Ice Sheet.

And we can see there a zoomed-in image to show how the north of Wales was covered by that ice sheet.

That's using geographic information systems, GIS, to add layers of information to maps.

Check for you now.

Glaciated landscapes are only found in polar regions.

Is that true or false, and why do you think that? Pause the video and come back when you're ready.

You should have said false, and your reason may have been something similar to this.

Glaciated landscapes include those that were shaped by glaciers in the past.

North Wales is an upland glaciated landscape.

During the Last Glacial Maximum, it was covered by the British-Irish Ice Sheet.

This massive ice sheet shaped the landscape seen today, carving out valleys, ridges, and other glacial features, well done.

Second check for you.

There are glaciers in North Wales.

True or false? Pause the video and make your decision.

You should have said false.

We call this, Eryri, a glaciated landscape due to the landforms that were created by glaciers in the past.

The last glaciers in North Wales disappeared at the end of the last ice age, well done.

We know that an area used to be glaciated due to the glacial landforms that remain there, and we can use GIS to visualise these landforms. Have a look at this little video clip.

Having watched that little video clip, here's a check for you.

Which of the following are glacial landforms found in North Wales? Hanging valley, a corrie or cwm, river, and truncated spurs.

Tick the ones that you think you saw in that video.

Pause the video and come back when you've made your decision.

You should have seen a hanging valley, a corrie, and truncated spurs.

Well done, you can always go back and watch it again if you didn't quite manage to see all of those.

First task for you now.

Describe the location of a glaciated landscape in the UK and identify two key features of the area formed by glaciation.

You should try to include the name of the glaciated landscape, where it is located in the UK, landforms of glacial erosion or deposition that are found here.

Pause the video and have a go at writing an answer to this question.

Your answer may look something like this.

The glaciated landscape in North Wales is mainly found in Eryri National Park.

It is located in the northwestern part of Wales.

Two key glaciated features in Eryri National Park are glacial troughs with steep sides and wide bases, and corries which are steep, bowl-shaped hollows found high up in the valleys, well done.

Let's now look at learning cycle two, using maps and GIS to identify glacial landforms. Glacial erosion and deposition creates landforms that can still be seen in a post-glacial landscape.

We have two images here.

The one on the left looks at a corrie formation during glaciation, so what it would've looked like when glaciers covered the ground.

And then a corrie that we're more familiar with now in the UK once the glaciers have retreated, so after glaciation.

But both these landscapes have been created by glaciers.

There are landforms created by glacial erosion, transportation and deposition across Eryri National Park in North Wales, and we're going to look at some examples of each of them.

A glacial trough in the Nant Ffrancon Valley, a corrie in Cwm Idwal, an arete called Crib Goch, a ribbon lake in the Nant Ffrancon Valley, and moraines and erratics around Cwm Idwal.

We can use OS maps, aerial photos, and GIS to become more familiar with their characteristics in North Wales.

This image here shows you an OS map and how we may use the contour lines, the grid references, the symbols, to help us to identify glacial landforms alongside GIS imagery.

Putting the two together really helps us to understand what these glacial landforms look like.

And we can see here we've got an arete identified, a pyramidal peak, and steep valley sides.

Yr Wyddfa is a pyramidal peak.

And a pyramidal peak is a sharply-pointed mountain peak that's created due to the formation of three or more corries.

We can identify on this OS map steep ground, the back walls of three corries, and we know this because the contour lines are very close together.

The pyramidal peak is central to this, and we can see that as it is marked by a spot height which shows us that the height at Yr Wyddfa is 1,085 metres above sea level.

Check for you now then.

Contour lines on an OS map can help us to identify glacial landforms. Pause the video and decide whether that is true or false and why.

You should have said true, and that's because they show relief, how the shape of the land has been changed through glacial processes.

So we could see on that map of Yr Wyddfa the steep back walls of the corries creating that pyramidal peak because the contour lines were very close together, well done.

Crib Goch is the arete situated to the northeast of Yr Wyddfa, so the Llanberis pass to the north and Llyn Llydaw to the south.

And we can see there its location on the map.

Crib Goch, situated to the north of Yr Wyddfa, is between the valleys of Nant Gwynant to the south and Llyn Llydaw to the east.

We can see it is the ridge between two steep-sided valleys with rocky terrain.

We can see that 'cause the contour lines are close together and the black symbols indicate loose rock or scree.

Cwm Idwal is located in the Glyderau range of mountains in northern Eryri.

And we can see there we've got a GIS image of it and the OS map.

We can see the bowl-shaped hollow marked by the semi-circular contour lines, the flatter base with the lake at the bottom as the contour lines are further apart and there's that blue colour showing us the lake, the steep back wall of the corrie shown with the contour lines being very close together.

Check for you now.

Can you complete the labels around this OS map that allow you to identify this corrie? Pause the video and come back when you've decided what the missing words are.

You should have added in semi-circular shaped contour lines, contour lines that are close together showing the steep back wall, a small lake in the centre where the contour lines are more widely spaced, well done.

The Nant Ffrancon Valley in northern Eryri was carved by a powerful glacier moving northwestwards.

We can use this GIS imagery to identify some of the key characteristics.

The broad, flat base of the valley, very steep sides, truncated spurs, hanging valley, a smaller tributary glacier flowing into the large one, and a ribbon lake, long, deep, narrow lake.

Let's look now at the OS map.

The broad, flat base of the valley is shown without many contours as they're widely spaced.

The steep sides are shown by the contour lines being very, very close together.

The truncated spur is shown with those flat-ended contour lines and there's also black marking showing scree and loose rock.

The hanging valley is shown with a smaller, steeper valley joining the larger one because the contour lines are close together and there is a stream flowing down into the valley.

The ribbon lake, the large narrow lake in the base of the glacial trough.

Check for you now.

This OS map extract shows a glacial trough found at the base of Cader Idris in Eryri National Park.

What key features do these arrows point to? Pause the video and come back when you've identified them.

You should have been able to identify the steep valley sides shown by the contour lines being very close together, the flat, broad valley base due to the lack of contour lines as they're more widely spaced, and the ribbon lake, Tal-y-Ilyn is a ribbon lake, so the large, narrow blue area at the base of the valley.

Moraines are a depositional landform and they can be seen on this 3D GIS image of Cwm Idwal.

A terminal moraine is found at the mouth of the corrie.

A 300-meter lateral moraine runs parallel to Lyn Idwal.

The moraine rises to 15 metres in height in places.

Scattered erratics can be seen across the Snowdonia landscape, left behind as the ice retreated.

Glacial erratic boulders perched at the side of Llyn Idwal can be seen in this photograph, but also on the OS map by the black circles.

Check for you now.

Can you identify the landforms created by glacial erosion in North Wales? Pause the video and come back when you've had a go.

You should have identified A as a corrie or cwm, B as a pyramidal peak marked by the spot height, and C as a glacial trough.

Well done if you managed to do that.

That's good knowledge of the characteristics of these landforms and how we interpret them on an OS map.

A final task for you now.

Can you identify and explain the formation of one glacial feature shown on these OS maps? And Sam says, "I must make sure I explain the processes of erosion and link them to the landforms they create." Pause the video and come back when you've had a go.

Your answer for this question may have included something like this.

A glacial trough, and in this case it's the Nant Ffrancon Valley.

So a glacial trough is formed when a glacier moves through a preexisting V-shaped valley.

Over time, the glacier deepens and widens the valley through processes such as plucking and abrasion.

Plucking occurs when the glacier freezes around rocks, pulling them out as it moves, while abrasion happens as rocks embedded in the glacier scrape and wear away the bedrock.

These processes transform the V-shaped valley into a U-shape with steep sides and a flat floor.

Well done, that's some really good geography.

Let's look now at a summary.

Eryri National Park is an example of an upland glaciated landscape in North Wales.

During the Last Glacial Maximum, it was covered by the British-Irish Ice Sheet.

Glacial erosion, transportation, and deposition processes have created many different landforms. Yr Wyddfa is a pyramidal peak, Crib Goch is an arete, Nant Ffrancon Valley is a glacial trough, Tal-y-Ilyn is a ribbon lake, Cwm Idwal is a corrie, and lateral and terminal moraines are found around it.

Well done, I hope now you feel more familiar with an example of an upland glaciated landscape and you're able to remember some of the specific names of these different landforms that we find in North Wales.

I look forward to seeing you again soon.