Glacial Landforms & Landscapes (Edexcel A Level Geography): Flashcards
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Define freeze-thaw weathering.
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Define freeze-thaw weathering.
Repeated freezing and thawing of water in rock cracks, where expanding ice exerts pressure, eventually breaking rock into sharp scree.
In carbonation, acidic rain reacts with in rocks to form soluble calcium bicarbonate.
In carbonation, acidic rain reacts with calcium carbonate in rocks to form soluble calcium bicarbonate.
What is a nivation hollow?
A nivation hollow is a depression formed beneath or beside snow patches by freeze-thaw, chemical weathering, and removal of debris by meltwater.
Describe plucking in glacial erosion.
Plucking occurs when basal meltwater refreezes around bedrock, then moving ice pulls away blocks, steepening valley sides and corrie back walls.
True or False?
Glacial abrasion produces rock flour and striations.
True.
Rock fragments in the glacier base grind bedrock, creating fine rock flour and linear striations showing ice flow direction.
In basal melting, increased lowers the melting point, producing meltwater that enables basal sliding.
In basal melting, increased pressure lowers the melting point, producing meltwater that enables basal sliding.
Define corrie (cwm/cirque).
A bowl-shaped hollow on a mountainside formed by rotational ice movement, plucking, and abrasion, often containing a tarn after glacial melt.
How does a U-shaped valley form from a river valley?
A V-shaped river valley is widened and deepened by powerful glacial erosion, producing a steep-sided, flat-floored U-shaped trough.
An arête forms when two erode back-to-back, leaving a narrow, knife-edge ridge.
An arête forms when two corries erode back-to-back, leaving a narrow, knife-edge ridge.
True or False?
A ribbon lake forms in over-deepened softer rock.
True.
Glaciers erode softer bedrock more deeply, and after melting, water fills these elongated hollows to form ribbon lakes.
Define glacial striations.
Linear grooves or scratches on bedrock produced as debris in the glacier base abrades the surface, indicating ice flow direction.
Define scouring in glacial landscapes.
The ability of ice masses to erode large areas of pre-existing landscape, especially when glaciers or ice sheets overspill their valleys.
What is a knock and lochan landscape?
A lowland area of rounded resistant rock hills (knocks) and small rock-basin lakes (lochans) formed by intense ice-sheet scouring.
In a crag and tail, the is resistant rock, and the is streamlined softer material behind it.
In a crag and tail, the crag is resistant rock, and the tail is streamlined softer material behind it.
True or False?
On a roche moutonnée, plucking occurs on the stoss side.
False.
On a roche moutonnée, the stoss side is smoothed by abrasion, while plucking creates a jagged lee side.
Define ice contact deposition.
Deposition of debris directly by the ice mass rather than by meltwater, producing features like erratics, moraines, and drumlins.
Define till.
Unsorted, irregular glacial debris ranging from clay to stones and boulders of any size and shape, deposited directly by ice.
What is an erratic in glacial landscapes?
An erratic is a boulder of different rock type to the local area, transported long distances by a glacier and deposited out of place.
True or False?
Erratics are usually deposited in clear, regular patterns.
False.
Erratics show no clear pattern of deposition and often appear randomly scattered across the landscape.
Name and locate three types of moraine on a glacier.
Lateral moraines form along valley sides, medial moraines in the centre where glaciers meet, and terminal moraines at the glacier snout.
Unsorted mounds of glacial till are called .
Unsorted mounds of glacial till are called moraines.
Describe the shape and structure of a drumlin.
A drumlin is an elongated, egg-shaped hill of till with a steep stoss side and a gently sloping, tapered lee side.
What is a till plain (ground moraine)?
A till plain is a wide area where till is spread across the valley floor as the ice mass retreats.
True or False?
Lodgement till is material forced into bedrock beneath slow-moving ice.
True.
Lodgement till is subglacial, unconsolidated material pressed or lodged into the bedrock under slow-moving glaciers.
Define ablation till.
Ablation till is supra and englacial debris deposited as the glacier melts, mainly at or near the ice surface.
How can drumlin swarms help reconstruct former ice movement?
The orientation shows ice-flow direction, and their elongation indicates ice velocity, so drumlin swarms help infer past glacier speed and pathways.
Define fluvioglacial landscape.
A fluvioglacial landscape is an area shaped by flowing meltwater and its erosional and depositional processes at or beyond a glacier’s margin.
How does surface meltwater reach subglacial meltwater tunnels?
Surface meltwater flows into crevasses and moulins, descends to the glacier base, then joins subglacial meltwater tunnels exiting at the snout.
What is basal sliding in warm-based glaciers?
Basal sliding occurs when meltwater lubricates the glacier base, reducing friction and allowing the glacier to move more easily over bedrock.
True or False?
Fluvioglacial meltwater flow is usually seasonal and dynamic.
True.
In temperate regions, meltwater varies seasonally, causing frequent changes in meltwater channel position and discharge.
How do fluvioglacial deposits differ from glacial till?
Fluvioglacial deposits are smaller, smoother, rounded, sorted and stratified. Glacial till is unsorted, angular and non-stratified.
Define glacial varves.
Glacial varves are annual layers of sediment in meltwater lakes, showing seasonal contrasts between coarse summer and fine winter deposition.
Fluvioglacial deposits are typically , , and .
Fluvioglacial deposits are typically smaller, smoother, and rounder.
Why are fluvioglacial deposits often well sorted and stratified?
Flowing meltwater sorts material by size and weight, depositing layers under varying seasonal discharges, creating horizontally sorted, stratified sediments.
Describe the proximal zone of an outwash plain.
In the proximal zone near the snout, meltwater velocity is high, carrying large, angular particles, sometimes mixed with till and forming alluvial fans.
Describe the distal zone of an outwash plain.
In the distal zone, drainage resembles normal rivers; outwash is well-sorted, smaller and rounded due to reduced velocity and longer transport.
True or False?
Imbrication shows clasts tilted upstream in fast meltwater.
True.
Imbrication occurs when elongated clasts overlap and dip upstream, indicating the direction and strength of meltwater flow.
In an outwash plain, coarse material is deposited and progressively finer material .
In an outwash plain, coarse material is deposited up-valley and progressively finer material down-valley.
Subglacial meltwater exits the glacier snout through under pressure.
Subglacial meltwater exits the glacier snout through meltwater tunnels under hydrostatic pressure.
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