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Describe the processes by which glaciers move. (6 marks).

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Introduction

Describe the processes by which glaciers move. (6 marks). Glacier movement depends on whether it is warm or cold. This depends on the pressure melting point (PMP), which is when ice is on the verge of melting. An increase in pressure can increase melting and therefore movement due to lubrication. Accumulation is the inputs of the glacier system by precipitation as snow, avalanches, debris as rocks and melt water. Ablation is the outputs of the glacier system which include melt water, till-rock deposition, calving iceberg, evaporation and wind erosion. If there is more accumulation than ablation then the glacier advances due to gravity. If there is less accumulation than ablation there is more melt water, which acts as a lubricant, the glacier then moves down the valley but retreats due to climate, altitude and latitude. ...read more.

Middle

When the gradient of the valley floor decreases, the ice slows down and becomes thicker (compressing flow). When the valley floor gradient increases the ice moves faster and becomes thinner (extending flow). Surges occur rarely (30-100years) when there is a huge movement in the glacier as there is instability due to a large rapid accumulation of snowfall. These are three main processes by which glaciers move. (b) Explain how landscape evidence can be used to identify the direction and extent of ice movement. (15 marks) Evidence of past glacial ice movement and the extent of the movement can be seen in the uplands and lowlands of mountains. The depositional features form glaciation and the beginnings of fluvial features can mark out the extent of the ice movement. ...read more.

Conclusion

Roche moutonnee are smooth rounded rocks that face the direction of the ice flow and are steep an jagged on the opposite side due to plucking. Erratics are boulders picked up by ice and deposited in areas of different lithology, once the origin of the boulder is identified it shows the extent of the ice movement. Some deposits in north Norfolk coast originated from southern Norway. Recessional, terminal, push and medial moraine make parallel high mounds of material extending across the valley or lowland area at right angles to and marking out the extent of the maximum ice movement as material would not be transported it further unless by fluvial processes. Drumlins are smooth elongated mounds of till which have long, gentle lee slope due the being streamlined by ice movement. Kettles are formed by detached blocks of ice left by the glacier as it retreats, once they melt it leaves enclosed depressions which fill with water to form kettle hole lakes. ...read more.

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