Periglacial Landforms

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Impermeable, permanently frozen ground

Covers approx 20% of earth surface

Three types:

  • Continuous: Coldest! Mean annual temp = -5°C to -50°C
    • no plant life
    • e.g. Artic Tundra
  • Discontinuous: Mean annual temp = -1.5°C to -5°C
  • Sporadic: Mean annual temp = 0°C to -1.5°C
    • Can sustain trees

Above permafrost = ACTIVE LAYER --> Seasonally thaws and is associated with mass movements

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Distinct and often symmetrical shape found in soils subjected to intense frost action.

  • Polygons and circles
  • Stripes on steeper slopes

Exact formation unknown, but suspected:

  • Repeated freeze thaw cycles smooth out irregularities and odd shaped piles
  • ice sorting
  • differential frost heave
  • solifluction
  • effect of vegetation
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"Flowing Soil"

The movement downwards under gravity of thawed soil over frozen ground. The liquid limit in the soil is exceeded causing it to flow - the speed of movement will depend on the slop angle

Seasonal Variability

  • Winter - water freezes in soil causing it to exapnd
  • Spring - Melts and flows downhill


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A landscape of hummocks and wet hollows, resulting from subsidence caused by the melting of permafrost.

May be caused by:

  • Broad climatic changes
  • Local environment changes
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A pingo (also called a hydrolaccolith) is a mound of earth-covered ice

An ice core is formed by the accumulation and freezing of water under pressure

Causes overlying sediment to rise forming a mound

Two Types:

  • Open-system: source of water is distant + elevated
  • Closed-system: source of water is local + pingo arises becaue of expansion of permafrost
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