The big idea: Glaciated and periglacial regions are shaped by ice.
A glacial environment is one that is covered by moving ice — glaciers erode, transport and deposit, carving out dramatic upland landscapes.
A periglacial environment is the cold fringe beyond the ice, underlain by permafrost (permanently frozen ground). Here it is the freezing and thawing of water in soil and rock — not flowing ice — that does the work.
Key terms for this micro
- Glacier — a slow-moving mass of ice that erodes, transports and deposits material.
- Permafrost — ground that stays frozen for two or more years; the surface layer that thaws in summer is the active layer.
- Freeze-thaw weathering — water freezes in cracks, expands and shatters the rock into angular fragments.
- Plucking — ice freezes onto rock and pulls it away as the glacier moves.
- Abrasion — rock embedded in the ice grinds the bedrock smooth, like sandpaper.
- Solifluction — the waterlogged active layer creeps slowly downslope over frozen ground in summer.
- Mass balance — the difference between accumulation (snow gained) and ablation (ice lost); it decides whether a glacier advances or retreats.
Ice that flows vs water that freezes: In a glacial landscape, moving ice erodes the land (plucking + abrasion → corries, aretes, troughs).
In a periglacial landscape, ice does not flow — instead the repeated freezing and thawing of water in the ground (freeze-thaw, solifluction, frost heave) builds the landforms.
How this is tested: Paper 1 Option C often asks you to Outline an erosional process and how it carves a landform, or to read a figure (a radial diagram of corrie directions, a photo of a glaciated valley). Always name the process and give the mechanism — naming alone scores nothing.
| Stage | What happens | Process at work |
|---|---|---|
| 1. Snow collects | Snow gathers in a shaded hollow on a mountainside and is compressed into ice | Accumulation |
| 2. Freeze-thaw at the back wall | Meltwater seeps into cracks, freezes, expands and shatters the rock | Freeze-thaw weathering |
| 3. Plucking deepens it | Ice freezes onto loose rock and pulls it away as the glacier moves, steepening the back wall | Plucking |
| 4. Abrasion scours the floor | Rock frozen into the ice base grinds the hollow, deepening it like sandpaper | Abrasion (rotational flow) |
| 5. A rock lip + tarn form | Erosion eases at the front, leaving a raised lip; when the ice melts a lake (tarn) fills the hollow | Rotational slip + deposition |
The two big erosion processes
- Plucking — meltwater freezes onto loose rock at the glacier base; as the ice moves it pulls the rock away, steepening the corrie's back wall.
- Abrasion — the rock now frozen into the ice acts like sandpaper, grinding and deepening the hollow as the glacier rotates.
- Freeze-thaw keeps feeding loose rock to the ice, so plucking and abrasion never run out of material.
Corries face the cold side: In the northern hemisphere most corries face north and east — the shaded, colder slopes where snow survives longest. A radial (rose) diagram of corrie directions shows this clustering: read the proportion facing each way straight off the rings.
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Beyond the ice sheets lies the periglacial zone — places like the Arctic tundra of Alaska and Siberia and the high Alps. The ground is frozen, but the top active layer thaws each summer, and it is this repeated freeze and thaw that shapes the land.
| Process | How it works | Landform it builds |
|---|---|---|
| Freeze-thaw weathering | Water in rock cracks freezes, expands ~9% and shatters the rock into angular fragments | Blockfields / scree / patterned ground |
| Solifluction | In summer the active layer thaws, becomes waterlogged and slowly creeps downslope over frozen ground | Solifluction lobes / terracettes |
| Ice segregation (frost heave) | Growing ice lenses push stones up and sort coarse from fine material at the surface | Patterned ground (stone circles, stripes) |
| Ground-ice growth | Water freezes under the surface and the expanding ice core domes the ground upward | Pingos |
| Thermokarst (thaw) | Ground ice melts, the surface collapses and hollows fill with water | Thermokarst lakes / subsidence |
Permafrost is a real challenge for people
- Arctic Alaska (the Prudhoe Bay oilfields) — pipelines must be raised on heated piles so the warm oil does not thaw the permafrost, which would cause the ground to subside and fracture the pipe.
- Siberia (Russia) — buildings are built on stilts so heat escaping from them does not melt the ground beneath and tip them over.
- The Alps — thawing of frozen rock (permafrost) on high peaks loosens the slopes and triggers rockfalls.
Why permafrost makes extraction hard: Heat from drilling, buildings and warm oil thaws the frozen ground. The thawed soil loses strength and the surface subsides, so foundations and pipelines crack. This is why Arctic infrastructure is insulated, raised or refrigerated — not because the frozen ground is simply 'too hard to drill'.
How this is tested — the [10] essay: Paper 1 Option C ends with a 10-mark markband essay — usually Examine or To what extent. Recurring versions: how important glacial erosion is in shaping upland landscapes (vs deposition, periglacial and fluvial action), and how central permafrost / freeze-thaw / solifluction are to periglacial landforms.
Top band needs: accurate terms, named landforms developed, a weighing of glacial erosion against other processes, and a clear judgement.
Landforms to bring as evidence
- Erosional: corrie, arete, pyramidal peak (horn), glacial trough (U-shaped valley), hanging valley.
- Depositional: moraine, drumlin, erratic — show that deposition shapes the lowlands.
- Periglacial: patterned ground, solifluction lobes, pingos — freeze-thaw and solifluction, not flowing ice.
Markband marks: (1) Develop named landforms (corrie, arete, trough), not just lists. (2) Weigh glacial erosion against other processes (deposition, freeze-thaw, rivers). (3) End on an explicit judgement that answers the command term.