Cold Environments: Periglacial Processes and Landforms

Cold Environments: Periglacial Processes and Landforms

1. Periglacial: Environments experiencing long cold winters and short warm summers, typically with permafrost but not covered by ice (glacial)

2. Permafrost

   • Ground that becomes permanently frozen to depths of over 100 meters.
   • Permafrost Table: The upper surface of the permafrost.
   • Active Layer: The top few centimetres of soil that may temporarily melt during summer, when temperatures briefly rise above 0 degrees C.

3. Periglacial Processes

   • Frost Shattering and Frost Heave
     • Frost Shattering: Water that expands when turned to ice-breaking apart rocks and sediments and forming a rock-strewn landscape called a felsenmeer
     • Leads to accumulation of scree at base of cliffs.
     • Frost Heave: Soils become very bumpy and irregular. Freezing soil water just below the surface expands and pushes up the ground above.
   • Nivation
     • Covers a range of processes associated with snow.
     • Includes the effects of frost shattering, which operates around the edges of the snow - gradually causing the underlying rock to disintergrate.
     • Meltwater removes any rock debris to reveal an ever enlarging nivation hollow.

4. Periglacial Landforms

   • Solifluction Lobes
     • Downslope movement of rock and soil material in response to gravity.
     • Occur in reasonably think and saturated active layer
   • Ice Wedges
     • Meltwater flows into cracks when permafrost contracts. The Meltwater refreezes in the winter to form ice wedges, which expand and force the cracks to widen.
     • Influence ground surface by forming narrow ridges - due to frost heave
   • Patterned Ground
     • As ice wedges become more extensive, a polygonal pattern may be formed on the ground surface-with ice wedges and their ridges marking the sides of the polygons
     • Stone Polygons
       • Stone Polygons tend to form on shallower slopes, and are directly associated with ice wedges. Frost heave causes expansions of the ground and lifts soil particles upwards.
   • Pingos
     • Water collects underneath the ground, as the sediment gradually freezes, the water collected becomes trapped and pressurized freezes as well.
     • This expansion causes the land to lift, creating a hill or mound
     • In the summer, the ice melts and forces the ground above to collapse inwards
     • Can be up to 60 meters high, and 600 meters in diameter.

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