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Glacier movement.

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Introduction

Glacier movement essay Distinguish between the terms accumulation and net ablation? (5) These are terms that identify with methods of adding of taking away the ice on a glacier, inputs and outputs if you will. Accumulation is a zone where snow collects either from a heavy downpour or an avalanche in sufficient quantities to remain long enough to be converted into firn. This is process that snow goes through before becoming ice. This is often on a plateau as the snow stands a higher chance of settling where as on a slope it is often disturbed. This often takes place in the winter. ON the other hand there is ablation is where mass leaves the glacier usually in the form of melt water in rivers. However some is lost due to evaporation and on coasts as icebergs. Ablation has a tendency to occur in the summer where temperatures are higher and therefore ice may melt and leave the glacier. ...read more.

Middle

Using modern equipment, scientists have recently found that glaciers move in TWO ways. Glaciers slide on water that has melted. They slide along the ground on a thin layer of melt water under the ice. This is known as basal sliding. Basal sliding, the second way ice moves, can happen several different ways. True basal sliding means that the base of the ice sheet is near the pressure melting point, and that some water is present. The pressure melting point is reached because high pressure actually reduces the temperature at which ice will melt. Ice at base of a 2200 meter (1.36 miles) thick ice sheet, will melt at -1.6�C (29.12�F), rather than at 0�C (32�F). The thicker the ice, the lower the temperature at which it will melt, and the higher the chance that some water will be available at the glacier base to enhance movement. Large parts of the West Antarctic Ice Sheet are at the basal melting point, so there may be large areas under the ice sheet where a thin water layer exists. ...read more.

Conclusion

The above are the processes by which glaciers move but the reasons behind why they move are simple geographical and physical reasons. Once a mass of compressed ice reaches a critical thickness, around 18 meters thick, it becomes so heavy that it begins to deform and move. The sheer girth of the ice, combined with gravity's influence, causes glaciers to flow very slowly. Ice may flow down mountain valleys; fan across plains, or in some locations, spread out to the sea. Movement along the underside of a glacier is slower than movement at the top due to the friction created as it slides along the ground's surface. Glaciers periodically retreat or advance, depending on the amount of snow accumulation or ablation that occurs. This retreat or advance refers only to the position of the terminus, or snout, of the glacier. Even as it retreats, the glacier still deforms and moves down slope, like a conveyor belt. For most glaciers, retreating and advancing are very slow occurrences, noticeable only over a long time. However, when glaciers retreat rapidly, movement may be visible over a few months or years. ...read more.

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