Using Case Studies And Examples, Describe And Explain The Landforms Found In The Glacial Landscape

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Using Case Studies And Examples, Describe And Explain The Landforms Found In The Glacial Landscape

It appears that roughly every 200-250 million years in the Earth's history there have been major periods of ice activity. The most recent of these occurred during the Pleistocene period of the Quaternary era. In the 2 million years since the onset of the Quaternary, there have been fluctuations in global temperature of between 5°C and 6°C, which have led to glacials and interglacials. In these periods, glaciers form and create many different landforms, either through erosion or deposition.

Glaciers are capable of moving large quantities of debris. The rock debris may be transported in one of three ways:

- Supraglacial debris is carried on the surface of the glacier as lateral and medial moraine

- Englacial debris is material carried within the body of a glacier

- Subglacial debris is moved along the floor of the valley by the ice, or by meltwater streams formed by pressure melting.

Ice that is stationary or contains little debris has limited erosive power, whereas moving ice carrying with it much morainic material can drastically alter the landscape. Virtually all the glacial processes of erosion are physical, as the climate tends to be too cold for chemical reactions to take place.

There are five main processes associated with glacial erosion:

- Frost Shattering

- Abrasion

- Plucking

- Rotational Movement

- Extending and Compressing Flow

These processes produce many different landforms. Two major erosional processes occur at the base of a glacier. At the base of a glacier, large amounts of rock and sediments are incorporated into the glacier's ice. The material in the ice then acts as an abrasive agent when combined with glacier movement. This process is known as abrasion. Abrasion creates a variety of features; the most conspicuous of these is striations. Striations appear as scratches of various sizes on rock surfaces. Striations can be found in virtually any glacial environment, a good example of these though is Lac Blanchet in Canada. In some cases, abrasion can polish the surface of some rock types smooth. This geomorphic feature is known as glacial polish. The abrasion also produces a fine clay-sized sediment that is often transported away from the glacier by meltwater. As a result of this process, glacial meltwater can have a light, cloudy appearance, and is called glacial milk.
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The second major erosional process that occurs at the base of a glacier is plucking. Plucking is the process of particle detachment by moving glacial ice. In this process, basal ice freezes in rock surface cracks. As the main body of the glacial ice moves material around the ice in the cracks is pulled and plucked out. The intensity of the plucking process is greatest on the lee-side of rock mounds. When combined with glacial abrasion, the action of plucking on rock mounds produces a unique asymmetrical feature known as Roche Moutonnee. Roche Moutonnee are smooth on the ...

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