Key Stage 3 geography · Physical geography

KS3 glaciation and glacial landforms: a guide for parents

In Key Stage 3, pupils learn how glaciers form, move and shape the land, and how the landscapes of upland Britain were carved by ice during the last Ice Age. They study erosion, transport and deposition by ice and learn to name and explain landforms such as corries, arêtes and U-shaped valleys. It matters because it shows how a process that has largely finished in Britain still explains the scenery that people live in and visit.

Glaciation and glacial landforms, explained

A glacier is a large body of ice that moves slowly downhill under its own weight. It begins where more snow falls in winter than melts in summer. The snow is buried by newer snow and compressed, first into grainy firn and then into solid ice. When the ice is thick enough, gravity makes it creep downslope, sometimes only centimetres a day. Today glaciers survive in high mountains and polar regions, but during the last glacial period they and bigger ice sheets covered most of Scotland, Wales and northern England, which is why Britain’s upland scenery holds so many glacial features.

Ice is a powerful agent of erosion. Pupils learn two main glacial processes. Plucking happens when meltwater freezes onto rock at the base of the glacier and, as the ice moves, pulls chunks of rock away. Abrasion happens when rock fragments frozen into the base and sides of the glacier scrape and scour the surface beneath, like sandpaper. Freeze-thaw weathering on the slopes above supplies even more rock debris. The glacier carries this material and, when the ice melts, drops it as a mixture of clay, sand and stones called till, in landforms known as moraines.

The most common landforms form a sequence in lessons. A corrie is an armchair-shaped hollow high on a mountain where snow collected and ice eroded the rock. When two corries form back-to-back, the narrow ridge between them is an arête, and where three or more corries cut into a mountain the peak left behind is a pyramidal peak. A glacier flowing down a river valley makes it wider and deeper, turning a V-shaped valley into a U-shaped valley with steep sides and a flat floor. Smaller valleys feeding into it are cut off and left as hanging valleys, often with waterfalls. A long, narrow ribbon lake can fill the deepened floor.

Lowland landforms matter too. Moraines mark where ice carried debris and left it as ridges. Drumlins are smooth, egg-shaped hills of till that tend to occur in groups, shaped by ice moving over them. Erratics are boulders carried far from where they came from and left stranded on different rock. Schools choose their own examples, and many pick an upland area such as Snowdonia (Eryri), the Lake District or the Scottish Highlands; others look at an alpine glacier. The programme of study asks pupils to understand how processes interact to produce distinctive landscapes that change over time, and glacial landscapes are a strong example.

Human geography also enters. Glaciated areas attract tourists, hill walkers and climbers, provide upland farming and water supply, and support hydroelectric power. Visitors can also damage footpaths and fragile habitats, and glaciers around the world are shrinking, which links back to the study of climate change. A good answer at this stage names a landform, explains how it formed in clear steps using the correct terms, and uses a real example where possible.

Words your child will hear

Glacier: A mass of ice that moves slowly downhill under its own weight.
Plucking: Rock pulled away when meltwater freezes onto it and the glacier moves on.
Abrasion: Scraping and scouring of rock by stones frozen into the base of the ice.
Corrie: An armchair-shaped hollow in a mountainside carved by ice. Sometimes called a cirque or cwm.
Arête: A sharp ridge left between two corries.
U-shaped valley: A wide valley with steep sides and a flat floor, formed by a glacier.
Till: Unsorted clay, sand and stones dropped by melting ice.

What the National Curriculum says

The programme of study for Key Stage 3 says:

Pupils should be taught to understand, through the use of detailed place-based exemplars at a variety of scales, the key processes in physical and human geography
Physical geography relating to: geological timescales and plate tectonics; rocks, weathering and soils; weather and climate, including the change in climate from the Ice Age to the present; and glaciation, hydrology and coasts
Pupils should understand how geographical processes interact to create distinctive human and physical landscapes that change over time.

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

A model answer: how is a corrie formed?

Describe and explain how a corrie is formed.

Find the starting point. A corrie begins in a hollow on a mountainside, usually on a slope facing away from the strongest sun, such as north-east. Snow collects there, and shade means it lasts through the summer.
Describe the ice. Over many years the snow is compressed into ice. The ice grows heavy enough to move, and instead of flowing straight downhill it turns in a slight rotating motion, called rotational slip.
Explain the erosion at the back. Plucking pulls rock from the back wall and abrasion scrapes it, making the wall steeper. Freeze-thaw weathering above the ice adds more rock debris to the glacier.
Explain the floor. Rock-laden ice grinds the base of the hollow, deepening it into a bowl. At the front, where the ice is thinner and has less erosive power, a rock lip is left.
Finish when the ice melts. After the glacier melts, water collects in the bowl behind the lip, forming a small lake called a tarn. The steep back wall, the bowl and the lip together make the corrie.

Snow gathers in a shaded hollow and turns to ice. Rotational movement, plucking and abrasion deepen the hollow and steepen the back wall, leaving a rock lip at the front. When the ice melts, a tarn fills the bowl. The result is an armchair-shaped corrie.

Common mistakes and how to help

Thinking a glacier is frozen solid and doesn’t move

Ice looks fixed, and pictures show only a still scene.

What helps: Glaciers flow, slowly but measurably, sometimes just centimetres a day. Crevasses, which are cracks, appear because different parts move at different speeds.

Believing U-shaped valleys were cut by rivers

Rivers cause most valley-shaping, so pupils assume they did this too.

What helps: Rivers in upland areas cut V-shaped valleys. A U-shaped valley with a flat floor and steep sides usually means a glacier once flowed through. Look at the profile in a photograph and decide which it is.

Picturing a glacier as a bulldozer that simply pushes rock aside

Diagrams often show ice as a smooth block moving across a surface.

What helps: The ice itself is fairly soft. Most of its erosive power comes from rock fragments embedded in it, which scratch the rock like sandpaper, together with plucking.

Thinking glacial landforms exist only where glaciers exist today

Pupils link “glacial” with ice they can see.

What helps: Many British landscapes were shaped by ice that melted more than 11,000 years ago. The landforms remain even though the ice has gone.

How to help at home

Make an abrasion block. Freeze some small gravel or sand into a block of water in a plastic tub. Once solid, rub it firmly over a bar of soap or a lump of soft clay and look at the scratches. This shows how embedded stones do the scouring.
Spot the profile. Look at photos of mountain valleys in a book or a walking guide and sort them into V-shaped and U-shaped. Ask your child which was carved by a river and which by ice, and what clues in the picture helped.
Model a valley in clay. Shape a V-shaped valley in a tray of soft clay, then press and drag a rounded spoon along it to widen it into a U. Name the parts: steep sides, flat floor and hanging valleys where small side channels end.
Look for erratics. Boulders in a field or park that don’t match the rock around them may be erratics. Ask your child how a boulder like that might have travelled, and what it tells us about where ice once flowed.
Plan a hill walk. If you visit upland Britain, take a map with you and find a corrie, a ribbon lake or a U-shaped valley. Check the weather forecast first, stay on paths and keep away from steep edges, and use the map to match what you can see to the landforms.

Builds on

Key Stage 2: Climate zones, biomes and vegetation belts
Key Stage 2: Rivers and the water cycle
Key Stage 2: Mountains
Key Stage 2: Volcanoes and earthquakes
Key Stage 2: Settlements and land use
Key Stage 2: Economic activity and trade
Key Stage 2: Natural resources