How do glacial and fluvioglacial processes create distinctive landforms, and how do these record past climate?
Erosional and depositional glacial landforms, periglacial landforms and fluvioglacial landforms; and how glaciated landscapes record Quaternary climate change.
An Eduqas A-Level Geography answer to glacial landforms and landscapes in Component 1, covering erosional landforms (corries, aretes, pyramidal peaks, U-shaped valleys), depositional landforms (moraines, drumlins, erratics), periglacial landforms and fluvioglacial landforms (eskers, kames, outwash), and how landscapes record Quaternary climate change, with UK examples.
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What this dot point is asking
Eduqas wants you to explain how glacial, periglacial and fluvioglacial processes create distinctive erosional and depositional landforms, and how the resulting landscapes record Quaternary climate change, distinguishing relict from active features.
The answer
Erosional landforms
Glacial erosion produces a recognisable upland suite. A corrie forms in a snow-collecting hollow as plucking steepens the back wall and abrasion deepens the floor, while rotational flow over-deepens the basin and leaves a rock lip. Where two corries erode back to back they leave a knife-edged arete, and where three or more meet they leave a pyramidal peak (a horn). Valley glaciers straighten and deepen former river valleys into steep-sided, flat-floored U-shaped valleys (glacial troughs), truncating interlocking spurs into truncated spurs and leaving tributary valleys as hanging valleys above the main trough. Smaller features include the roche moutonnee, with a smooth, abraded up-valley (stoss) side and a steep, plucked down-valley (lee) side.
Depositional, periglacial and fluvioglacial landforms
Periglacial landforms form in cold, non-glaciated ground where intense freeze-thaw and seasonally frozen ground (an active layer over permafrost) operate: patterned ground (sorted circles and polygons from frost heave), solifluction lobes (slow downslope flow of saturated, thawed soil) and ice-wedge polygons. The key distinction Eduqas tests is between unsorted, angular till dumped directly by ice and the sorted, rounded, layered sediment laid down by meltwater.
Recording Quaternary climate change
The Quaternary has seen repeated glacial and interglacial cycles, and the landscapes of upland Britain (Snowdonia, the Lake District, the Scottish Highlands) are relict, cut by Pleistocene ice and abandoned as the ice melted at the start of the present interglacial. Reading the limits of till and terminal moraines maps former ice extent, and the freshness of corries and troughs records the most recent glaciation. These landscapes are best understood as a palimpsest: an inherited record of past climate, overprinted by present-day weathering, mass movement, fluvial action and human use.
Examples in context
Example 1. Snowdonia, North Wales. Snowdonia is a classic relict glaciated upland. Cwm Idwal is a textbook corrie with a steep back wall and a tarn in its over-deepened basin; sharp aretes such as Crib Goch radiate from the pyramidal peak of Snowdon; and Nant Ffrancon is a deep U-shaped glacial trough with truncated spurs and hanging tributary valleys. None of these is being cut today, so Snowdonia is read as a record of the last Pleistocene glaciation, exposed and weathered since the ice melted. It is the most-used Eduqas case for the erosional suite.
Example 2. The Lake District and its depositional record. The Lake District combines erosional troughs (radiating from the central fells) with a depositional record on its lower ground: drumlins in the lowland valleys record the direction of ice flow by their streamlined long axes, erratics of distinctive Lake District rock are found far to the south, and moraines mark former ice limits. Fluvioglacial outwash sands and gravels lie beyond the moraines. Together the erosional uplands and depositional lowlands let students reconstruct ice extent and flow, the synoptic skill of reading a glaciated landscape as a climate archive.
Try this
Q1. Distinguish between a terminal moraine and a lateral moraine. [2 marks]
- Cue. A terminal moraine is the ridge of till deposited at the furthest point (snout) the glacier reached; a lateral moraine is the ridge of till deposited along the sides of the glacier.
Q2. Explain why fluvioglacial deposits are sorted while till is unsorted. [3 marks]
- Cue. Fluvioglacial deposits are laid down by meltwater, which sorts and rounds particles by size and deposits them in layers; till is dumped directly by ice with no water sorting, so it is a mix of angular particles of all sizes.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 2019 (style)6 marksExplain the formation of a corrie.Show worked answer →
Sequence the processes that hollow out and steepen a corrie.
Snow accumulates in a north or east-facing hollow, is compacted into ice, and freeze-thaw weathering and plucking steepen the back wall while abrasion deepens the floor.
Rotational movement of the ice deepens the basin and leaves a rock lip at the front, so that after deglaciation a circular tarn often fills the over-deepened hollow.
A located example such as a Snowdonia or Lake District corrie secures the marks.
Markers reward a sequenced, process-led explanation linking plucking, abrasion and rotational flow to the landform.
Eduqas 2022 (style)12 marksAssess the extent to which glaciated landscapes are best understood as a record of past climate change.Show worked answer →
A 12-mark extended response requiring a judgement.
Argue that many landforms record past climate directly: relict U-shaped valleys, corries and moraines in upland Britain were cut by Pleistocene ice and abandoned as the climate warmed, and the limits of till and outwash mark former ice extent.
But qualify: contemporary glaciated landscapes are still active, periglacial processes continue in some areas, and human activity (tourism, reservoirs) and present-day processes also shape the landscape, so it is not only a relict climate archive.
Conclude that glaciated landscapes are best understood as a palimpsest, an inherited record of Quaternary climate overprinted by ongoing process, with the relict climate signal strongest in deglaciated uplands and weakest where modern processes dominate.
Markers reward a balanced, exemplified judgement.
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Sources & how we know this
- Eduqas A-level Geography specification (from 2016) — Eduqas (2016)