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The Lake District, Snowdonia, the Cairngorms, Loch Lomond and the Trossachs and the Brecon Beacons.
In the past, many of the UK's great National Parks were shaped by the action of glaciers.
With corries, U-shaped valleys, pyramid peaks and arêtes, the large-scale landforms, that dominate these landscapes are magnificent sculptures carved out by flowing ice.
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But the more subtle features of these landscapes also have their own story to tell.
Look down this valley, it's a U-shaped valley that's been carved out by a glacier.
And down in the centre of the valley, we can actually see a depression, where a small glacier sat just 11,500 years ago, right at the end of the last ice age.
But if we look more closely, we can see that the bottom of the U-shaped valley isn't smooth.
We can see these lumps and bumps in the foreground, we can see these distinct ridges in the background.
What are these features?
Why are they here?
Let's go and take a closer look and find out what they're made of.
So we're down here on one of these subtle ridges down in the valley bottom.
And we've actually come right down to the stream, where the flow of water has been cutting, or incising down into the material and we can see what it's made of.
This type of sediment looks really familiar to me.
I've seen similar kinds of sediment, that are deposited at the margins of modern day glaciers in places like Iceland, Norway and Greenland.
And if we look closely, we can see how this sediment is made up of a mixture of fine sediment, of pebbles, of large boulders, and we call these types of sediment glacial till.
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So how does this glacial till get here?
This is how glaciers begin, as pristine ice, where snow has accumulated in a depression on a hill slope and then becomes compressed into ice over time.
As the glacier flows down the valley, it erodes the valley floor.
It picks up or entrains this sediment to produce dirty ice at the base of the glacier, a bit like this block of ice that we've picked out of the river.
This sediment is then transported down to the glacier margin or to the terminus.
And at the snout of the glacier, as the ice melts, this sediment is released to produce this glacial till.
So the glacier acts a bit like a conveyor belt, eroding, transporting and then depositing sediment.
This glacial sediment accumulates at the margin or the edge of the glacier to produce landforms that we call moraines.
Now in this Lake District valley, we can actually see several different types of moraine all created by the glacier in slightly different ways.
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So right at the end of the last ice age, a little glacier formed here in this valley.
It started up there in the cirque and it flowed right down the centre of the valley, and this is where the glacier came to a stop.
This mound or pile of material is made of glacial till and we call it a terminal moraine, deposited at the end or the snout of the glacier.
The terminal moraine reaches right across the centre of the valley.
But since the last ice age, the river flowing down this valley has been eroding away or incising the centre of the valley, and it's cut this moraine in half at its centre.
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We can actually see two terminal moraine ridges, which are parallel to each other.
And if we look at Skeiðarárjökull in Iceland, we can see as many as fifteen terminal moraine ridges.
These illustrate what we call a punctuated retreat: the glacier retreats during the summer and experiences little re-advances during the winter.
We call this recessional moraine and this shows how the glacier retreats and advances, as it responds to changes in climate.
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As the glacier here flowed down the valley, it scraped material, tearing rock and soil away from the valley side.
The glacier also made the sides of the valley steeper, and mass movements like landslides and rockfalls occurred.
We can actually see all this material from that erosion and the mass movements, still piled up here along the valley side.
This long ridge, this long mound is called a lateral moraine and it would have run along the side of the glacier.
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So like most valleys that have been glaciated, this valley actually has two lateral moraines running down the sides of it.
The lateral moraines come down either side of the valley and then they actually curve round to come together and meet in the middle, as part of the terminal moraine.
This big, curved deposit of glacial till tells us where the glacier came up to, when it was here at the end of the last ice age.
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Just like the tributaries of rivers, two glaciers can come together to produce a larger glacier.
In these situations, the lateral moraines come together as well to produce a medial moraine, that flows down the centre line of this larger glacier.
We often see these medial moraines on the surface of modern day glaciers.
However, they tend to be destroyed as the glacier recedes and as the ice melts.
So we don't see medial moraines in landscapes like this, where the ice melted several thousand years ago.
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There's also another type of moraine here, which is actually less well known.
Look at this chaotic, bumpy ground all around us.
It's not a nice straight line of terminal or lateral moraine, but it is made of glacial till.
This is called hummocky moraine and it was formed when a big part of the glacier broke off.
It probably became stuck on some rough ground or broke away from the main glacier and came to a stop right here.
The ice then melted, dropping all the sediment it was carrying, creating these lumps and bumps on the surface of the landscape.
This hummocky moraine is really the sign of a dying glacier, right at the end of its life.
So we've looked at the formation of different types of moraine.
Terminal moraine, which is deposited at the snout of the glacier and it runs right across the middle of the valley.
Recessional moraines, where we have a sequence of end moraines, that show how the glacier margin has retreated over time.
Lateral moraines, which have been carved from the valley sides and they run right down the valley from top to bottom.
And medial moraines, where these lateral moraines come together and the sediment is transported down the centre of the valley.
And finally hummocky moraine, where part of the glacier has broken away and melted, leaving a chaotic mess of sediment and creating bumpy ground.
By thinking like geographers, we can make sense of these smaller, more subtle landforms, that help to reveal the hidden secrets of our landscape's glacial past.
Every lump and bump in the landscape is actually there for a reason.
You can get out and explore our National Parks.
Or even start by exploring the entire planet, using a geographical information system, and see if you can spot these kinds of landforms and make sense of the story that they have to tell.
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