13.3 Periglacial Processes and Landforms

Periglacial environments are cold, non-glacial areas with unique landforms shaped by frost action and permafrost. These regions, found in high latitudes and elevations, experience intense freezing-thawing cycles that create distinctive features like patterned ground and pingos.

Permafrost, a defining characteristic of periglacial environments, plays a crucial role in shaping landscapes and influencing geomorphological processes. As climate change causes permafrost to thaw, it impacts ecosystems, infrastructure, and greenhouse gas release, making the study of these regions increasingly important.

Periglacial environments and characteristics

Definition and location

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• Periglacial environments are cold, non-glacial areas characterized by intense frost action, permafrost, and unique landforms
• Typically found in high-latitude regions or at high elevations
  • Arctic
  • Antarctica
  • Alpine areas

Climate and temperature

• Long, cold winters and short, cool summers
• Mean annual temperatures below freezing

Permafrost

• Ground that remains frozen for at least two consecutive years
• Defining feature of periglacial environments

Geomorphological processes

• Driven by frost action
  • Freezing and thawing cycles
  • Frost heaving
  • Solifluction

Frost action in periglacial processes

Definition and mechanisms

• Physical weathering processes that occur due to the freezing and thawing of water in rocks, soils, and sediments
• Frost shattering
  • Water freezes and expands in rock cracks and crevices, causing the rock to break apart
• Frost heaving
  • Upward movement of soil or sediment caused by the formation of ice lenses during freezing conditions
• Frost creep
  • Slow downslope movement of soil particles due to repeated freezing and thawing cycles
• Solifluction
  • Downslope movement of water-saturated soil or sediment over permafrost or seasonally frozen ground
• Cryoturbation
  • Mixing of soil layers due to frost action, resulting in the formation of patterned ground and other periglacial features

Formation of periglacial features

Patterned ground

• Distinct geometric shapes formed on the ground surface
  • Circles
  • Polygons
  • Stripes
• Sorted patterned ground
  • Stone circles and polygons
  • Larger stones pushed to the edges by frost heaving, smaller particles settle in the center
• Non-sorted patterned ground
  • Frost boils and earth hummocks
  • Fine-grained soils subjected to intense frost action and cryoturbation

Pingos

• Ice-cored hills that form in permafrost regions
• Pressurized water freezes and pushes up the overlying soil and sediment
• Hydraulic pingos
  • Water under pressure freezes in a confined space (lake bed) and pushes up the overlying sediment
• Hydrostatic pingos
  • Groundwater under pressure is forced to the surface and freezes, creating a mound of ice and soil

Permafrost significance in periglacial environments

Landscape and geomorphological processes

• Shapes the landscape and influences geomorphological processes
• Affects hydrology by creating an impermeable layer
  • Restricts water infiltration
  • Promotes surface runoff
• Acts as a barrier to plant root growth
  • Limits vegetation cover
  • Influences the distribution of plant communities

Climate change impacts

• Thawing of permafrost due to climate change
  • Ground subsidence
  • Thermokarst formation
  • Release of greenhouse gases (methane and carbon dioxide)
• Permafrost degradation impacts on infrastructure
  • Buildings
  • Roads
  • Pipelines
  • Structural instability and damage

Importance of studying permafrost dynamics

• Understanding potential impacts of climate change on sensitive ecosystems and human activities
• Crucial for predicting and mitigating the consequences of permafrost thaw in periglacial regions