How do glacial systems create distinctive landscapes and landforms?
How glacial and periglacial erosion, transport and deposition create erosional, depositional, fluvioglacial and periglacial landforms.
An Edexcel A-Level Geography answer to how glacial systems shape the land, covering erosion, transport and deposition and the erosional, depositional, fluvioglacial and periglacial landforms they create using Cwm Idwal, Helvellyn and Icelandic sandur.
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What this dot point is asking
Edexcel wants you to explain how glacial systems shape the land through erosion, transport and deposition, and how these create erosional, depositional, fluvioglacial and periglacial landforms. You need the processes, the landforms in each group at macro, meso and micro scale, and named examples.
Glacial erosion, transport and deposition
Erosion has two main processes. Plucking (or quarrying) occurs where meltwater freezes onto loosened, jointed rock and the moving ice pulls it away, steepening back walls. Abrasion is the grinding of the bed by debris embedded in the base of the ice, smoothing and scratching it. Crushing breaks rock under the ice's weight, and subglacial meltwater lubricates movement and flushes debris.
Transport carries debris in three positions: supraglacial (on top, from frost-shattered valley sides), englacial (within the ice) and subglacial (dragged along the bed). Deposition of this debris produces till, an unsorted mix of all sizes laid down either as lodgement till (plastered onto the bed beneath moving ice) or ablation till (dropped as the ice melts). The key contrast with rivers is that till is unsorted, whereas meltwater (fluvioglacial) deposits are sorted by size.
Erosional and depositional landforms
Erosional landforms span three scales. Macro features include U-shaped troughs (glacial valleys), hanging valleys (tributaries left high above the main trough), truncated spurs (interlocking spurs sheared off by ice) and fjords (drowned troughs). Meso features include corries (cirques), armchair hollows often holding tarns; aretes, knife-edge ridges between two corries; pyramidal peaks, formed where three or more corries meet; and roches moutonnees, asymmetric bedrock bumps smoothed by abrasion on the up-ice side and plucked on the down-ice side. Micro features include striations (scratches recording ice direction) and crag and tail (a resistant crag sheltering a tapering tail of softer rock or till).
Depositional landforms include moraines (terminal at the snout, recessional marking pauses, lateral along the sides, medial where two laterals merge, and ground moraine beneath), drumlins (streamlined till mounds, blunt up-ice and tapering down-ice) and flat till plains.
Fluvioglacial and periglacial landforms
Meltwater and frozen ground create their own distinctive landforms beyond the ice itself.
Fluvioglacial landforms include kames (mounds of sorted sediment), kame terraces (along valley sides), eskers (sinuous subglacial stream ridges), outwash plains or sandur (flat sorted gravels beyond the snout), kettle holes (hollows from melted buried ice) and varves (annual sediment layers in proglacial lakes). Periglacial landforms form in frozen ground beyond the ice: ice wedges and patterned (polygonal) ground from repeated freezing, pingos (ice-cored mounds), blockfields of frost-shattered rock, solifluction lobes from slow downslope flow of saturated soil, and thermokarst where ground ice thaws.
Examples in context
Example 1: Cwm Idwal and Helvellyn. Cwm Idwal in Snowdonia is a classic corrie holding Llyn Idwal, ringed by aretes and plucked back walls, with striations and roches moutonnees nearby recording ice flow. In the Lake District, Red Tarn sits in a corrie below Helvellyn, flanked by the aretes of Striding Edge and Swirral Edge where adjacent corries cut back to back, textbook upland erosional landforms.
Example 2: Norwegian fjords and Icelandic sandur. Sognefjord in Norway is a 200 km drowned glacial trough over 1 km deep, the deepest fjord, showing macro-scale erosion. In Iceland, the meltwater plains in front of glaciers such as Solheimajokull are extensive sandur, flat sheets of sorted outwash gravel braided by meltwater streams, the classic fluvioglacial landscape.
Try this
Q1. Explain how plucking and abrasion combine to form a roche moutonnee. [4 marks]
- Cue. Abrasion smooths the up-ice (stoss) side; plucking steepens the down-ice (lee) side, giving the asymmetric bedrock bump.
Q2. Outline how you would tell a fluvioglacial landform from a glacial depositional landform in the field. [4 marks]
- Cue. Check the sediment: sorted, layered sand and gravel is fluvioglacial (esker, kame, sandur); unsorted till of mixed sizes is glacial (moraine, drumlin).
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel Paper 1 (style)12 marksAssess the relative importance of erosion in producing distinctive glaciated landscapes.Show worked answer →
AO1 should set out glacial erosion (plucking and abrasion), transport and deposition, while AO2 weighs erosion against deposition and fluvioglacial action. Erosion produces the most striking landforms: U-shaped troughs, corries, aretes and pyramidal peaks, well shown at Cwm Idwal in Snowdonia and Helvellyn with Red Tarn in the Lake District. Plucking and abrasion together carve and smooth these features, with striations recording ice direction.
A balanced judgement (AO3) notes that deposition (moraines, drumlins, till plains) and fluvioglacial processes (eskers, kames, outwash plains such as Icelandic sandur) are equally responsible for the lowland glaciated landscape. The supported conclusion is that erosion dominates upland landscapes while deposition and meltwater dominate lowland ones, so importance depends on location within the glacial system.
Edexcel 20198 marksExplain how a corrie is formed by glacial processes.Show worked answer →
AO1 and AO2. Explain that snow accumulates in a north or east-facing hollow, compacting into ice. Rotational sliding and abrasion deepen the hollow while plucking steepens the back wall, and freeze-thaw above the ice feeds debris in. When the ice melts, an armchair-shaped hollow remains, often holding a tarn dammed by a rock lip or terminal moraine.
Apply a named example. Red Tarn below Helvellyn in the Lake District sits in such a corrie, with the aretes of Striding Edge and Swirral Edge formed where adjacent corries cut back to back. Conclude that the combination of rotational movement, abrasion and plucking, with freeze-thaw weathering, produces the distinctive corrie form.
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Sources & how we know this
- Pearson Edexcel A-Level Geography (9GE0) specification — Pearson Edexcel (2016)