Describe and explain the variety of landforms found in periglacial areas.

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Describe and explain the variety of landforms found in periglacial areas

The term periglacial literally means ‘around the ice’. Periglacial regions are characterised by persistently low temperatures, but are not covered by glacial ice. The processes associated with periglacial regions, usually take place in areas where the mean annual air temperature is below 3ºC. Such areas usually experience short cool summers and long cold winters. At present, areas such as the Tundra of northern Russia, the USA and Canada, together with high mountainous regions such as the Alps, experience a periglacial climate.

There are a number of different processes, which produce these periglacial landforms. These processes are frost action including shattering (wedging and splitting), heave and cracking, mass movement including solifluction, nivation and fluvial processes.

Frost action is one of the most important processes in periglacial regions, which results in the physical breakdown of rocks into finer particles as water turns to ice and expands. Frost action can also cause the ground surface to expand upwards by up to 5cm per year, a process known as frost heave. In some periglacial areas, frost heave produces irregular, hummocky surfaces covered with small frost mounds.

Frost action is responsible for the development of patterned ground, an array of small-scale, geometric features found at the surface of a regolith that has been disturbed by frost action. The group includes circles, polygons, and nets, which normally occur on level or gently sloping surfaces, and steps and stripes, which are found on steeper gradients. Both sorted and non-sorted varieties are recognized. The sorted varieties are typically outlined by coarse, stony material.

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There are two types of patterned ground. There are small dome shaped polygons and stripes due to frost sorting and there are large polygons with raised edges due to frost wedging/ice contraction. The first type, existing due to the process of frost sorting, is a result of the heave/thrust of stones to the surface, causing surface sediments to be up domed, followed by surface sorting. This occurs on slopes of less than 6º, and the polygons can be 1-5m in diameter. Elongated stripes are formed on slopes with a gradient over 6º. In autumn and winter, ice layers form in ...

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