Periglacial Processes

Geography: Edexcel A Level, topic 2.2.1

Periglacial Locations

Periglacial environments are currently widespread in high altitude and high latitude locations.

Periglacial environments are found at high latitudes, especially in the Arctic.
They are less common in the Southern Hemisphere because of the absence of land masses between 60°S and 70°S - it is mostly ocean!

Periglacial environments are found at high altitudes because temperatures are low (they fall by 1°C for every 100 m of height).
E.g. the Himalayan Plateau.
Periglacial environments are also found in continental interiors, away from the moderating influence of the sea.
E.g. Siberia.

Permafrost is permanently frozen ground, of which there are three types.

Continuous permafrost covers the largest areas with air temperatures below -5°C. The ground can be frozen to depths of several hundred metres.
Discontinuous permafrost occurs over smaller areas with mean air temperatures between -5°C and -1.5°C. Its depth is much shallower, up to 35m.
The surface tends to melt in summer and rivers and lakes cause the permafrost to be absent around them due to their ‘warming’ effect.
Sporadic permafrost covers the smallest areas where mean air temperatures are between -1.5°C and 0°C. Permafrost occurs only in markedly cold spots.

Permafrost has a seasonal (summer) active layer.
This is the upper layer which seasonally melts.
The depth varies from a few centimetres to several metres, depending on the average summer temperature.
This layer can become waterlogged (due to meltwater not being able to drain away).
This can cause it to be unstable and move, even on low angle slopes.

Periglacial environments are widespread in high altitude and high latitude locations today. They are characterised by distinctive processes.

Major periglacial processes are highly seasonal and are dependent on annual cycles of freezing and thawing.
Nivation is the collection of seasonal snow in hollows which encourage frost weathering beneath them.
Frost heave is the upward movement of soil due to the growth of lenses of ice in the soil. The lenses grow due to capillary movement of water in the soil.
Freeze-thaw weathering is the alternate freezing and thawing of water in cracks and crevices within rocks which causes them to split.

Solifluction is the downslope movement of saturated soil, on slopes with a gradient as low as 1 degree.
Erosion by high winds describes fine particles that may be blown away by strong winds on featureless plains.
Meltwater erosion describes strong flows of meltwater in the spring and summer washing away weathered material as well as eroding river banks.

Why are periglacial environments found at high altitude?
Which of these is an example of a continental interior where you would find a periglacial environment?
In which of the following locations would you find more periglacial environments?
What depth of ground is frozen in discontinuous permafrost?
What do we call the collection of seasonal snow in hollows which encourages frost weathering beneath?