13.3 Periglacial Processes and Landforms
3 min read•july 30, 2024
Periglacial environments are cold, non-glacial areas with unique landforms shaped by and permafrost. These regions, found in high latitudes and elevations, experience intense freezing-thawing cycles that create distinctive features like and .
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
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- 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
Key Terms to Review (16)
Active layer: The active layer is the uppermost layer of soil in a permafrost region that thaws during the warm months and refreezes in the winter. This layer is crucial for understanding periglacial processes, as it plays a significant role in shaping landforms and affecting vegetation dynamics in cold climates. The thickness and characteristics of the active layer can vary based on factors such as climate, soil composition, and topography.
Continuous permafrost: Continuous permafrost is a type of permafrost that remains frozen year-round and covers large areas of the Arctic and sub-Arctic regions. This layer of permanently frozen ground is characterized by its consistent thickness, typically exceeding 1,500 meters in some places, and has significant implications for landforms, hydrology, and ecosystems in these cold environments.
Cryogenic environment: A cryogenic environment refers to conditions in which temperatures are extremely low, typically below -150°C (-238°F), causing the physical properties of materials, biological organisms, and geological processes to change dramatically. In such environments, permafrost and other frozen ground conditions prevail, shaping unique landforms and influencing periglacial processes.
Cryoturbation: Cryoturbation is a periglacial process that involves the mixing and disturbance of soil and sediment due to freeze-thaw cycles in cold environments. This process results in the movement of soil particles and can create distinctive landforms, such as patterned ground and frost mounds. It plays a significant role in shaping the landscape and influencing ecosystem dynamics in areas affected by permafrost.
Frost Action: Frost action refers to the mechanical weathering process that occurs when water infiltrates cracks in rocks, freezes, and expands, causing the rocks to fracture and break apart. This phenomenon plays a crucial role in periglacial environments, where repeated freeze-thaw cycles contribute to the formation of distinctive landforms and sediment characteristics, impacting soil development and landscape evolution.
Gelifluction: Gelifluction is the process of soil and sediment flow that occurs in periglacial environments, particularly in areas with seasonal freezing and thawing. This phenomenon is characterized by the slow movement of water-saturated soil or debris downhill due to the effects of gravity, often forming distinctive landforms like gelifluction lobes. Understanding gelifluction is essential in examining how periglacial landscapes evolve and how climate change can impact these sensitive regions.
Ice segregation: Ice segregation is a periglacial process where ice forms within the soil and causes the separation and upward movement of soil particles. This occurs when water in the soil freezes and expands, creating ice lenses that push the surrounding soil upwards, leading to unique landforms. This process significantly influences soil structure and contributes to the development of patterned ground features in periglacial environments.
Ice wedges: Ice wedges are vertical, crack-like features that form in permafrost regions when the ground expands and contracts due to freeze-thaw cycles. These structures develop as water infiltrates the cracks during warmer months and freezes during colder months, leading to the growth of wedge-shaped ice masses that can significantly influence landscape morphology in periglacial environments.
Infrastructure vulnerability: Infrastructure vulnerability refers to the susceptibility of built environments and essential systems, such as roads, bridges, utilities, and buildings, to damage or failure due to environmental stresses or climatic changes. In the context of periglacial processes and landforms, this vulnerability is exacerbated by freeze-thaw cycles, ground movement, and other permafrost-related phenomena that can severely impact infrastructure stability and functionality.
Patterned ground: Patterned ground refers to a distinctive landform created in cold climates, characterized by the arrangement of soil and sediment into various geometric shapes. These patterns often develop due to freeze-thaw cycles, where repeated freezing and thawing of the ground causes materials to shift and rearrange, creating features such as polygons, stripes, or circles. The presence of patterned ground is an indicator of periglacial processes at work in an area, showcasing how climate impacts landscape formation.
Periglacial Climate: A periglacial climate is characterized by areas that are influenced by the presence of permafrost, where temperatures remain below freezing for extended periods, but are not consistently cold enough to support glacial conditions. This climate type is often found in high-latitude regions, where the ground remains frozen beneath a layer of active soil that thaws during the warmer months. The periglacial environment creates unique landforms and processes due to the freeze-thaw cycles and the interplay between ice, soil, and vegetation.
Pingos: Pingos are dome-shaped mounds formed in permafrost regions, typically characterized by a core of ice surrounded by soil. These landforms arise from the freezing of groundwater or from the pressure exerted by underlying ice, which can cause the ground to heave upwards, creating a distinct shape. Pingos are important indicators of periglacial processes and serve as key features in the study of cryospheric environments.
Resource extraction effects: Resource extraction effects refer to the environmental, social, and economic consequences resulting from the extraction of natural resources such as minerals, fossil fuels, and timber. These effects can significantly alter landscapes, disrupt ecosystems, and impact local communities, particularly in periglacial regions where fragile environments are more susceptible to disturbance.
Subarctic climate: A subarctic climate is characterized by long, harsh winters and short, cool summers, typically found in high-latitude regions just below the Arctic Circle. This climate type experiences significant temperature variations between seasons, with average winter temperatures often dropping below freezing and summer temperatures rarely exceeding 10 to 15 degrees Celsius. Precipitation in subarctic regions is generally low, with most falling as snow during the winter months, influencing periglacial processes and landforms in these areas.
Tussocks: Tussocks are clumps of dense vegetation, typically consisting of grasses or sedges, that grow in wetland areas and can be prominent in periglacial environments. They play a significant role in stabilizing soil, promoting water retention, and providing habitat for various species. In periglacial settings, tussocks can also influence the microclimate and hydrology of the area, affecting other forms of vegetation and landscape features.
Vegetation adaptation: Vegetation adaptation refers to the various modifications and adjustments that plant species undergo in response to their environment, allowing them to survive and thrive in specific conditions. These adaptations can be physiological, morphological, or behavioral, and are crucial for plants to cope with factors such as temperature, moisture availability, and soil composition, especially in extreme environments like periglacial regions.