some of the glacial landforms
1. Corrie
erosional
- Build up of snow over a winter
- Firn
- The snow builds up
- Condenses into compact ice
- Nivation occurs, along with plucking and abrasion of the walls
- After the glacier melts, a corrie is left
2. Esker
Depositional
Large debris at the start of the easker, finer towards the end – ‘sorted deposition’
Periglacial landscape
- Deposition of till, and debris from the meltwater at the bottom of the valley on the valley floor – subglacial –
- Material in the subglacial stream comes from the glacier
- Sinuous – continuous line – where the stream would have been
3. rouche moutonee
erosional
in a glacial valley in a band of hard rock
- When the glacier is moving down the valley
- Hits a rock it cannot move, meets pressure melting point
- Meltwater moves over rock and refreaazes on the other side – basal sliding
- Plucking occurs taking the face off one of the rocks, leaving the aspect facing (lee) against the glacier untouched and the aspect facing the direction of flow is eroded (stoss)
4. Patterened ground
Periglacial
- When there is so much melt water, rocks are lifted from the soil to the surface, to create
- Permafrost area – freezing and thawing
- Fost heave – upwards and outward movement of the ground when the soil freezes
5. Pingo
Periglacial
Rounded ice-cored hills that can be can be as much as 90m in height and 800m in diameter
Formed by ground ice which develops during the winter months as temperatures fall.
- Open-system pingos form in valley bottoms where water from the surrounding slopes collects under gravity, freezes and expands under artesian pressure. The overlying surface material is forced to dome upwards.
- Closed-system pingos develop beneath lake beds where the supply of water is from the immediate local area. As permafrost grows during cold periods, groundwater beneath a lake is trapped by the permaforst below and the frozen lake above. The saturated talik, or unfrozen ground, is compressed by the expanding ice around it and is under hydrostatic pressure. When the talik itself eventfully freezes it forces up the overlying sediments.
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6. Pyrimidal peak
erosional
- When two or more glaciers meet.
- The back of the corrie receeds
- One or two other corries do the same, leaving a pyrimidal peak behind
- The faces experience plucking and abrasion – causing the steep degrees of the slopes
7. Drumlin
Depositional
- Deposition of firn and till from the glacier
- A mound of glacial debris that has been streamlined into an elongated hill.
- Often they are prominent landforms sometimes more than 1km in length and 100m high.
- They are pear shaped and aligned in the direction of ice flow.
- Their formation is not fully understood. They may be formed by:
- lodgement of subglacial debris as it melts out of the basal ice layers
- reshaping of previously deposited material during a subsequent re-advance
- accumulation of material around a bedrock obstruction - rock-cored drumlins
- thinning of ice as it spread out over a lowland area, reducing its ability to carry debris.
- Drumlins tend to occur in large groups or swarms, forming a so-called 'basket of eggs' topography.
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8. Kames
Depositional
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9. Terminal moraine
Depositional
- When the glacier looses kinetic energy and deposits the debris it has picked up along its journee
- Creates a cresent shape at the bottom of the valley from the deposit left
10. Ellipsoidal basin
Erosional
The lip of the basin where the glacier starts
- major erosional landforms created by ice sheets (rather than valley glaciers).
- The Laurentide ice sheet which existed between 95,000 - 12,000 years ago is responsible for forming a number of ellipsoidal basins including the Great Lakes along the Canada/USA border and the finger lakes of New York State shown in the image.