Periglaciation

Periglacial means 'near to or at the fringe of an ice sheet, or often used to describe any area that has a cold climate. I will now just give a brief description of the different permafrost zones that lie in the Arctic regions of Canada, the USA and Russia.

Permafrost

• Permafrost is permanently frozen ground.
• It can be found where soil temperatures remain below freezing point for at least two consecutive years.
• It covers over 25% of the Earth's landscape, as shown below a considerable area of the Arctic is covered by continuous, discontinuous and sporadic permafrost, as shown below.

Continuous permafrost

• Found mainly within the Arctic circle.
• Mean annual temperature is below -5 degrees, winter temperatures may fall to -50 degrees
• Summers are too short to allow anything but a superficial melting of ice.

Discontinuous permafrost

• This form of permafrost lies further south in the northern hemisphere, reaching 50 degrees North of central Russia. It has a mean annual temperature of of between  of -1 degrees centigrade and -5 degrees centigrade. Discontinuous permafrost consists of islands of permanently frozen ground and separated by less cold areas which lie near rivers, lakes and seas. 

Sporadic permafrost

• The mean annual temperature are just below freezing point.
• It is an area where summer temperatures are above freezing. The surface layer thaws to form the active layer. This area is often saturated with meltwater, as it cannot infiltrate downwards through the impermeable permafrost. It is unlikely to evaporate or to drain downhill since most of the slopes are very gentle. This stationary meltwater is the main reason behind periglaciated areas containing many of the world's few remaining wetland environments.

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