Periglacial landforms

• What are periglacial landforms?

  Areas with permafrost, seasonal temperature variations, and freeze-thaw cycles dominating geothermal processes
• What is permafrost?


  Permanently frozen ground that is either frozen continuously or discontinuously for at least 2 years
• Where are periglacial landforms typically found?

  High latitudes (Antarctica), continental areas (Siberia), and high mountainous areas at lower latitudes (Alps)
• What percentage of the Earth’s land surface is covered in periglacial landforms?

  25%
• How does climate influence periglacial landforms?

  Temperatures must be between -6°C in winter to 0°C in summer
• Which process is dominant in periglacial environments?

  Freeze-thaw weathering
• What is frost heave?

  A subsurface process that leads to a vertical sorting of material in the active layer
• What is patterned ground?

  Rock particles distributed across the ground in a system of polygons and circles
• How is patterned ground formed?

  Through frost heave, where repeated cycles of freezing and thawing cause large stones to reach the surface and form a network of stone polygons
• Typically, how big is each stone polygon in patterned ground?

  1. 2 metres in diameter
• Give a named example of where patterned ground is found.

  Barrow, Alaska
• What are pingos?


  Rounded, dome-shaped ice core hills
• How are open system pingos formed?

  Water seeps into upper layers under artesian pressure, accumulates, and freezes, causing the overlying layers to dome
• How are closed system pingos formed?

  In continuous permafrost, unfrozen lakes drain, causing the lake bed to freeze and form an ice lens that expands and domes the surface
• What is continuous permafrost?

  Permafrost where there is little thawing, even in summer, often found in high altitude and latitude areas
• What is discontinuous permafrost?


  Permafrost with some patches of consistent permafrost, broken up by talik extending to the active layer
• What is the active layer?

  The thawed surface layer where plants can live for at least part of the year
• What is talik?


  Unfrozen ground beneath the ice surface
• What is deglaciation?


  The process when most landforms are viable, usually during ablation periods