Periglacial Environments

Periglacial Environments

1. Distribution

   • Approx 20% of earths land experience periglacial conditions
   • Alaska, Siberia, Canada

2. Characteristics

   • Long cold winters. temperatures are rarely abouve 0 and at times may fall below -50.
   • Mean monthy temperature is less than -3, short summers and mean annual precipitation is less than 1000mm

3. PERMAFROST!!!

   • Continuous
     • Formed in the coldest areas where permafrost is thick sheet with no gaps and in areas with temperature as low as -40C
   • Discontinuous
     • permafrost is fragmented by warmer areas like nearer rivers and the coast.
     • Tend to be warmer areas
   • Permafrost is frozen ground, where the subsoil and underlying rock remain frozen for two consecutive years

4. PROCESSES

   • Freeze-Thaw Action
     • This process is when the temperature changes during the day and evening and freezes water that is in a crack and causes it to expand
     • Causes Scree slopes
   • Groudwater Freezing
     • This occurs when its cold enough for water within the active layer to freeze and expand which can lead to lumps, ie. PINGOS
   • Frost Cracking
     • this is similar to freeze-thaw except the ground is already frozen
     • Can lead to Ice Wedges
   • Frost Heave
     • This is the upward movement of material due to the expansion of freezing water underneath.
     • Causes stone sorted polygons
   • Nivation
     • The collective set of proesses which occur beneath snow patches . it consists of freeze-thaw and chemical weathering

5. PROCESSES

   • Scree Slopes
     • Largest boulders are at the base of the slope because they travel further
   • Pingos
     • Isolated hills containing a core of ice.
   • Ice Wedges
     • Areas of layered ice occupying deep cracks.
   • Patterned Ground
     • As the active layer freezes it causes slopes which then the rocks that appear from frost heave will roll down forming shapes.