What is What is a corrie (cwm)??

An armchair-shaped hollow in a mountainside formed by glacial erosion — rotational flow deepens the floor, plucking steepens the back wall.

Glacial Landforms — GCSE Geography Revision

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The basics

Snowdonia's Secret History

🏔️ Snowdonia's Secret History

Standing on the summit of Snowdon — Yr Wyddfa in Welsh — you are on a jagged peak shaped not by volcanic fire or shifting tectonic plates, but by ice. The hollow below to your left is Glaslyn, a dark and still lake occupying a corrie: an armchair-shaped hollow carved by a rotating mass of glacier ice. The valley behind you is U-shaped — wide, flat-bottomed, and steep-sided, cut through solid rock not by any river but by a glacier hundreds of metres thick. Every feature of this landscape is a geological record of the last ice age, which ended around 10,000 years ago. It took roughly 100,000 years to carve.

Glacial landforms are divided into two groups: erosional landforms, created as the glacier wore away rock (found primarily in upland areas), and depositional landforms, created when the glacier dropped its load of debris (found in both upland and lowland areas). For the OCR B J384 and AQA 8035 specifications, you need to know how each was formed and be able to name real UK examples. This topic covers all of them.

What is an arête?: A narrow, knife-edge ridge between two corries or glacial valleys, formed when glaciers erode from both sides of a ridge.

Key terms

Geography glossary

What is an arête?: A narrow, knife-edge ridge between two corries or glacial valleys, formed when glaciers erode from both sides of a ridge.
What is a corrie (cwm)?: An armchair-shaped hollow in a mountainside formed by glacial erosion — rotational flow deepens the floor, plucking steepens the back wall.

Spotlight

The Big Picture: Erosional vs Depositional

Before diving into individual landforms, it helps to understand the fundamental division that underpins the whole topic:

Exam tip

Earn the mark scheme marks

🧠 CATCH A DRUM — The Complete Glacial Landforms Mnemonic

Learn all the main glacial landforms in one mnemonic: CATCH A DRUM. The first five letters cover erosional upland features; the last five cover depositional features.

C — Corries (cirques/cwms) — armchair-shaped hollows formed by rotational flow + plucking + abrasion. Usually contain a tarn (corrie lake). North/northeast-facing in UK. Red Tarn (Helvellyn) and Glaslyn (Snowdon) are your named examples.

A — Arêtes — knife-edge ridges between two corries eroding from opposite sides. Striding Edge, Helvellyn = your named UK arête.

T — Truncated spurs — cliff-like triangular rock faces where glacier cut off interlocking spurs. Found on the sides of U-shaped valleys (e.g. Nant Ffrancon, Snowdonia).

C — Corrie lakes / Tarns fill the over-deepened hollow — when the glacier retreats, the rock lip retains meltwater. This also acts as a reminder that corries lead to tarns.

H — Hanging valleys — tributaries left hanging above the main U-valley floor because smaller glaciers eroded less deeply. Marked by waterfalls (e.g. Pistyll Rhaeadr, 73 m, Wales).

A — sAndar / Alluvial outwash — sorted, stratified fluvioglacial sediment deposited by meltwater rivers beyond the glacier snout. Flat, braided rivers, grades from coarse to fine.

D — Drumlins — smooth oval hills of till, stoss end upstream. Tell you the direction of past ice flow. Eden Valley, Cumbria = UK drumlin field. "Blunt end faces the attacker."

R — Ribbon lakes — long, narrow lakes in over-deepened glacial troughs. Often moraine-dammed at one end. Windermere (17 km, longest lake in England) is your named example.

U — U-shaped valleys (glacial troughs) — the master erosional landform. Flat floor, steep sides, misfit stream on the floor. Nant Ffrancon (Snowdonia) and Langdale (Lake District) are your named examples.

M — Moraines (and pyramidal peaks) — moraines are ridges of till marking retreat stages: lateral (valley sides), medial (centre), terminal (maximum extent). M also reminds you of the Matterhorn = pyramidal peak (3+ corries eroding one peak). Snowdon = UK pyramidal peak equivalent.

Additional memory tricks:

Till vs outwash: "Till is UNsorted like a builder's skip — everything dumped together. Outwash is SORTED like supermarket shelves — like sizes together."
Corrie → arête → pyramidal peak: "One glacier digs a bowl. Two glaciers carve a blade. Three glaciers make a crown."
Kettle holes: "A kettle hole forms where dead ice melts — the ground kettles (sinks) into the gap left by the vanishing ice."
Eskers: "An esker is a river's fossil — the sediment a subglacial river left behind when the ice melted and its tunnel walls dissolved."

Now try it yourself

Quiz · Question 1 of 17

What is the name for the small lake that forms in the floor of a corrie after glaciation?

Tap an answer to check it

This topic in real past papers

Every real exam question we've found on glacial landforms, with a full worked answer.

AQA Paper 1

Whenever a student answers Question 5 (Glacial), it includes a 4 mark question explaining the formation of a specific glacial landform, always level marked across two bands.

4 marks

AQA Paper 1

Whenever a student answers Question 5 (Glacial), it closes with a 6 mark question on tourism, development or conservation in glaciated upland areas, always using a given figure and an example.

6 marks

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