8.3 Periglacial landforms and processes
4 min read•july 30, 2024
shape cold, non-glaciated environments through intense and permafrost. These features, like and , form unique landscapes that provide insights into past and present conditions.
Freeze-thaw processes drive the creation of these landforms, with factors like and influencing their development. Understanding these processes helps predict landscape changes and potential hazards in periglacial regions, especially as climate shifts.
Periglacial Landforms
Types of Periglacial Landforms
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- Periglacial landforms develop in cold, non-glaciated environments characterized by intense frost action and permafrost presence
- Patterned ground forms geometric surface patterns through (stone circles, polygons, stripes)
- lobes create slow-moving, tongue-shaped masses of soil and rock debris on slopes due to freeze-thaw cycles
- form vertical, wedge-shaped ice bodies in permafrost regions through repeated frost cracking and ice growth
- Pingos develop ice-cored hills in permafrost areas from upward growth of massive ice lenses
- topography produces irregular depressions and hummocks from thawing of ice-rich permafrost
- generate lobate or tongue-shaped bodies of frozen debris moving downslope by internal ice deformation
Characteristics and Significance
- Periglacial landforms indicate past or present cold climate conditions
- These features provide insights into permafrost distribution and active layer dynamics
- Patterned ground variations reflect differences in soil composition and moisture content
- Solifluction lobes serve as indicators of slope instability in periglacial environments
- Ice wedges preserve paleoclimate information through their growth patterns and isotopic composition
- Pingos act as freshwater sources in arid periglacial regions (North Slope of Alaska)
- Thermokarst features highlight areas vulnerable to permafrost degradation
- Rock glaciers store significant amounts of water in arid mountain environments (Andes, Alps)
Formation of Periglacial Landforms
Freeze-Thaw Processes
- pushes soil particles and rocks upward when water freezes and expands in soil
- mixes and churns soil through repeated freeze-thaw cycles, crucial for patterned ground development
- initiates ice wedge and polygonal ground pattern formation from rapid cooling and shrinking of frozen ground
- Frost sorting separates coarse and fine materials in the active layer, creating stone circles and other patterned ground features
- Solifluction causes downslope movement of saturated active layer soil and debris during thaw periods
- Thermokarst processes melt ground ice, leading to surface subsidence and characteristic depressions and lakes
- Segregation ice lens growth in frost-susceptible soils contributes to frost heaving and various periglacial landform development
Environmental Factors
- Climate controls the intensity and frequency of freeze-thaw cycles (Arctic, Antarctic, high mountain environments)
- Soil properties influence susceptibility to frost action and (silt-rich soils are highly frost-susceptible)
- Topography affects drainage patterns and slope processes in periglacial environments
- impacts ground thermal regime and soil moisture content
- influences weathering rates and sediment supply for periglacial landform development
- play a role in ice segregation and pingo formation
- affects ground thermal insulation and processes
Frost Action in Periglacial Landscapes
Mechanical Weathering and Soil Disturbance
- Frost action breaks down rocks through freeze-thaw cycles and frost wedging, contributing to
- Ice segregation forms ice lenses causing significant frost heaving and soil disturbance
- Cryoturbation mixes and churns soil, developing patterned ground and disturbing soil horizons
- Combined effects of frost action, ice segregation, and cryoturbation create unique geomorphic processes shaping periglacial landscapes
- These processes form characteristic (earth hummocks, )
- Climate, soil properties, and topography influence the intensity and frequency of frost action processes
- Understanding these processes helps predict landscape evolution and potential hazards in periglacial environments, especially considering climate change
Impact on Vegetation and Ecosystems
- Frost action creates microhabitats for specialized plant communities adapted to periglacial conditions
- Cryoturbation affects soil nutrient cycling and organic matter distribution in periglacial
- Frost heaving can damage plant roots and affect vegetation patterns in tundra environments
- Solifluction processes influence plant succession and community composition on slopes
- Thermokarst development can lead to rapid changes in local hydrology and vegetation patterns
- Permafrost thaw releases stored carbon, potentially impacting global climate systems
- Periglacial processes create unique ecosystems supporting specialized flora and fauna (Arctic fox, musk ox)
Periglacial Processes and Landscape Evolution
Sediment Transport and Erosion
- Periglacial processes significantly weather and break down bedrock, producing transportable sediment
- Solifluction and act as important mass wasting processes, moving large sediment volumes downslope
- Nivation erodes and transports sediment by snow patches, forming nivation hollows
- Wind action in periglacial environments creates and transports fine-grained sediments, contributing to loess deposits
- in periglacial regions show high seasonal variability, with nival regimes dominating river discharge patterns
- Interaction between periglacial processes and other geomorphic agents (fluvial, aeolian) creates complex landscape evolution patterns
- Periglacial landforms and sediments provide valuable paleoenvironmental information for past climate and landscape change reconstruction
Long-term Landscape Development
- Periglacial processes contribute to the overall of landscapes over geological time scales
- Repeated cycles of freeze-thaw action gradually break down bedrock, creating extensive and
- form through long-term frost action and slope processes in periglacial environments
- Periglacial activity can modify pre-existing landforms, such as glacial features in paraglacial settings
- The development of thick permafrost can preserve ancient landscapes beneath ice-rich sediments ( in Siberia)
- Climate oscillations between glacial and interglacial periods drive cycles of periglacial landscape development
- Understanding periglacial landscape evolution helps interpret past environmental conditions and predict future changes in cold regions
Key Terms to Review (39)
Bedrock composition: Bedrock composition refers to the underlying solid rock layer beneath soil and loose material at the Earth's surface. This composition plays a crucial role in shaping landscapes, influencing the types of periglacial landforms and processes that develop in cold environments, such as frost action and the formation of patterned ground.
Blockfields: Blockfields are extensive areas of fragmented rock debris that accumulate in cold environments, particularly in periglacial regions. They are formed through freeze-thaw processes where repeated freezing and thawing of moisture within rock cracks leads to the disintegration of the rock, creating a landscape dominated by large, angular blocks. These blockfields are often associated with the active layer of permafrost and serve as important indicators of past and present climate conditions.
Climate: Climate refers to the long-term average of weather conditions, including temperature, humidity, wind, and precipitation, in a specific region over extended periods, typically 30 years or more. Understanding climate is essential because it influences various earth surface processes, such as soil formation, slope stability, the development of periglacial landforms, and karst processes that involve dissolution chemistry.
Cryophilic organisms: Cryophilic organisms are life forms that thrive in extremely cold environments, often found in permafrost, polar regions, and glacial areas. These organisms have adapted to survive and reproduce in temperatures that can drop below freezing, showcasing unique biological processes that allow them to withstand such harsh conditions. Their presence is significant in understanding ecosystem dynamics and the potential impacts of climate change on these fragile habitats.
Cryoplanation terraces: Cryoplanation terraces are flat or gently sloping landforms that develop in periglacial environments, resulting from a combination of freeze-thaw cycles and the processes of erosion and sedimentation. These terraces typically form on the surface of slopes and are characterized by their stepped appearance, created as materials are weathered and transported downhill by gravitational forces and frost action. They illustrate how climatic conditions influence landscape evolution in cold regions.
Cryoturbation: Cryoturbation refers to the mixing and disturbance of soil and sediment caused by freeze-thaw cycles in periglacial environments. This process is significant in shaping the characteristics of these regions, as it alters the soil structure, affects vegetation patterns, and influences the development of specific landforms. Cryoturbation plays a key role in periglacial environments where seasonal temperature fluctuations lead to the formation of features like patterned ground and thermokarst.
Denudation: Denudation is the process through which the Earth's surface is worn away, leading to a reduction in elevation and the removal of soil and rock material. This process can occur due to various natural forces, including weathering, erosion, and mass wasting, and plays a crucial role in shaping landscapes over time. Understanding denudation helps in recognizing how landforms evolve and change in response to climatic and geological factors.
E. M. Johnson: E. M. Johnson was a prominent geographer and researcher known for his contributions to the understanding of periglacial processes and landforms. His work focused on how cold climates shape the landscape, particularly in areas affected by freeze-thaw cycles, which are critical to the formation of periglacial features such as solifluction lobes and patterned ground.
Ecosystems: Ecosystems are dynamic systems composed of living organisms and their physical environment, interacting as a functional unit. They encompass the relationships among various biotic components, such as plants, animals, and microorganisms, along with abiotic factors like soil, water, and climate. The interplay between these components shapes the processes that sustain life, such as nutrient cycling and energy flow, which are essential in understanding how environments evolve and respond to changes.
Erosion: Erosion is the process by which soil, rock, and other surface materials are worn away and removed from their original location by natural forces such as water, wind, ice, or gravity. This process is essential in shaping landscapes and influencing sediment transport, which connects various components of the Earth's surface system.
Fluvial Processes: Fluvial processes refer to the various ways in which rivers shape the landscape through the movement of water, sediment, and other materials. These processes include erosion, transportation, and deposition, which work together to create and modify landforms along riverbanks and floodplains. Understanding fluvial processes is essential for grasping how rivers influence both periglacial environments and broader geomorphological features.
Frost action: Frost action refers to the mechanical weathering process that occurs when water seeps into cracks in rocks and soil, then freezes and expands, causing the material to fracture and break apart. This phenomenon is particularly significant in periglacial environments, where temperatures fluctuate around freezing, creating ideal conditions for repeated freeze-thaw cycles that shape the landscape and influence landforms.
Frost boils: Frost boils are small, circular mounds that form in periglacial environments due to freeze-thaw cycles and soil movement. These features arise from the repeated expansion and contraction of water within the soil, which pushes particles upward and creates distinct surface patterns. Frost boils are indicative of the dynamic processes occurring in cold regions, reflecting the interaction between temperature fluctuations and soil composition.
Frost Heaving: Frost heaving is a geological process where soil or pavement is lifted upwards due to the expansion of freezing water in the ground. This phenomenon primarily occurs in periglacial environments, where freeze-thaw cycles create conditions that cause water to migrate and freeze beneath the surface, leading to the uplift of materials. It plays a critical role in shaping the landscape, influencing soil structure, and affecting human infrastructure.
Frost sorting: Frost sorting is a process where soil and sediment particles are segregated by size due to freeze-thaw cycles, which leads to the movement of materials and the formation of distinct patterns on the ground surface. This sorting occurs primarily in periglacial environments, where temperatures fluctuate around freezing, causing water in the soil to freeze and thaw repeatedly. The movement and sorting of particles contribute to the unique landscape features characteristic of these regions.
Gelifluction: Gelifluction is the process of soil or sediment flow caused by the freeze-thaw cycles in periglacial environments, leading to the movement of water-saturated materials down slopes. This phenomenon occurs when the upper layer of ground thaws while the underlying permafrost remains frozen, allowing the saturated soil to become unstable and flow downhill, creating distinctive landforms. Gelifluction plays a crucial role in shaping landscapes and influencing the stability of periglacial environments.
Groundwater dynamics: Groundwater dynamics refers to the movement, distribution, and quality of groundwater within the subsurface. This process is influenced by factors such as recharge, discharge, aquifer properties, and hydraulic gradients, which all play critical roles in shaping the behavior of water beneath the Earth's surface. Understanding groundwater dynamics is essential for assessing water availability, managing resources, and evaluating the impacts of climate and human activities on hydrological systems.
Ice segregation: Ice segregation is a periglacial process where ice forms within soil or sediment, leading to the redistribution of water and soil particles due to freezing and thawing cycles. This process is critical in shaping periglacial landforms as it influences soil structure, ground stability, and vegetation patterns in cold regions. As ice segregates, it can create features like frost heave and patterned ground, which are key indicators of freeze-thaw dynamics in permafrost-affected areas.
Ice wedges: Ice wedges are vertical, wedge-shaped cracks that form in the ground due to the freeze-thaw cycles in permafrost regions. These features develop when moisture in the soil freezes, causing the ground to expand and crack, ultimately leading to the formation of ice-filled fissures. Ice wedges are significant indicators of permafrost dynamics and contribute to unique landforms in periglacial environments.
Mechanical weathering: Mechanical weathering is the process of breaking down rocks and minerals into smaller fragments without changing their chemical composition. This physical breakdown can occur through various natural forces, such as temperature fluctuations, frost action, and abrasion, leading to the formation of sediments. In periglacial environments, where freeze-thaw cycles are common, mechanical weathering plays a significant role in shaping the landscape and creating distinctive landforms.
Microrelief features: Microrelief features refer to small-scale topographical variations in the Earth's surface, typically created by processes such as freeze-thaw action, frost heaving, and cryoturbation. These features include forms like patterned ground, ice wedges, and solifluction lobes, which provide insight into past and present periglacial conditions. The study of these features helps to understand the influence of cold climate processes on landscape evolution.
Nivation: Nivation is a geomorphological process that occurs in areas where snow accumulates, resulting in the formation of features like nivation hollows or cirques. This process involves the combination of freeze-thaw cycles, snow melt, and the chemical weathering of the underlying substrate, which leads to erosion and the development of distinct landforms. Nivation plays a crucial role in shaping periglacial environments by contributing to soil movement and altering the landscape.
Patterned ground: Patterned ground refers to the distinctive surface features found in periglacial environments, resulting from freeze-thaw cycles and the movement of soil and rocks. These features often include polygons, stripes, and other geometric shapes formed due to the differential movement of materials in response to temperature changes, playing a crucial role in understanding the dynamics of permafrost and landforms in cold climates.
Periglacial landforms: Periglacial landforms are features created by processes related to freeze-thaw cycles and permafrost in cold, typically subarctic regions. These landforms arise from the unique physical and chemical weathering effects that occur in areas where the ground remains near or below freezing for extended periods, leading to distinctive landscape features like patterned ground and solifluction lobes.
Pingos: Pingos are mounded landforms found in permafrost regions, formed by the expansion of ice beneath the surface, which causes the ground to bulge upward. These unique structures showcase the interactions between permafrost dynamics and geological processes in cold environments. Pingos can indicate the presence of permafrost and reveal important insights into the characteristics of periglacial environments and their associated landforms and processes.
R. D. McCulloch: R. D. McCulloch was a prominent geographer and researcher known for his contributions to understanding periglacial landforms and processes. His work emphasized the importance of freeze-thaw cycles and their influence on landscape formation in cold climates, providing insights into how these processes create unique landforms such as patterned ground and solifluction lobes.
Rock glaciers: Rock glaciers are unique landforms found in periglacial environments, characterized by a mixture of rock debris and ice that moves slowly down slope due to gravity. These formations result from the interaction of ice and rock in cold climates, where permafrost conditions are prevalent, playing a crucial role in understanding both the physical landscape and the processes that shape it over time.
Sediment transport: Sediment transport refers to the movement of solid particles, typically resulting from processes such as erosion, weathering, and deposition, through various environmental mediums like water, wind, or ice. This process is crucial for shaping landscapes and influencing ecological systems, as it plays a key role in sediment delivery to river channels, coastal areas, and other depositional environments.
Snow cover distribution: Snow cover distribution refers to the spatial extent and variability of snow accumulation across a given landscape, influenced by factors such as topography, climate, and vegetation. This distribution plays a crucial role in various environmental processes, including hydrology, ecosystem dynamics, and periglacial landform development, as the presence and characteristics of snow cover can significantly affect ground temperatures and freeze-thaw cycles.
Soil properties: Soil properties refer to the physical, chemical, and biological characteristics of soil that influence its behavior and suitability for various uses. These properties play a crucial role in understanding how soil interacts with water, plants, and the environment, making them essential for assessing land use, agriculture, and ecosystem health.
Solifluction: Solifluction is a type of mass wasting process characterized by the slow, downslope flow of water-saturated soil and sediment, particularly in periglacial environments. This process typically occurs in areas with a layer of frozen ground beneath the active layer, causing the upper soil layers to become saturated during warmer months and slowly flow downhill due to gravity. Understanding solifluction is important because it highlights how periglacial conditions influence landforms and processes, while also linking to broader environmental changes.
Thermal contraction cracking: Thermal contraction cracking refers to the process where the ground, particularly in periglacial environments, undergoes cracks due to temperature drops, causing materials to shrink. As temperatures fall, the volume of soil and rock diminishes, leading to stress within these materials that can result in visible fractures. This phenomenon is significant in understanding how periglacial landforms develop and evolve over time.
Thermokarst: Thermokarst refers to a type of landform that develops in periglacial environments due to the thawing of ice-rich permafrost. This process results in the uneven subsidence of the ground, creating features such as depressions, mounds, and lakes. The formation of thermokarst significantly impacts the landscape and hydrology, contributing to various landforms and processes that define periglacial regions.
Topography: Topography refers to the arrangement of the natural and artificial physical features of an area, including its landforms, elevations, and depressions. It plays a crucial role in influencing soil formation, determining climate and vegetation patterns, and shaping the characteristics of periglacial environments, where the landscape is heavily affected by freeze-thaw cycles and ice processes. Understanding topography helps explain the distribution and creation of various landforms and processes occurring in these unique settings.
Tors: Tors are isolated rock outcrops that rise prominently from the surrounding terrain, commonly formed in granite or other igneous rock landscapes through processes like weathering and erosion. They are significant features in periglacial environments, often serving as indicators of past glacial activity and providing unique habitats for flora and fauna adapted to harsh conditions.
Tundra vegetation: Tundra vegetation refers to the unique plant life that thrives in the cold, harsh conditions of the tundra biome, characterized by a short growing season, permafrost, and low temperatures. This vegetation is adapted to survive extreme environmental stresses, and it plays a crucial role in the periglacial landscapes, influencing soil stability and local ecosystems.
Vegetation Cover: Vegetation cover refers to the layer of plant life that covers the ground in a specific area, playing a crucial role in environmental processes. It affects soil formation, influences hydrological cycles, and interacts with erosion and landform development. The type and extent of vegetation cover can significantly impact ecological dynamics, climate regulation, and land use practices.
Ventifacts: Ventifacts are stones or rock surfaces that have been shaped and polished by the wind, often seen in arid or semi-arid environments where wind erosion is prevalent. These formations are created when particles carried by wind impact the surface of rocks, gradually wearing them down and sculpting them into unique shapes. This process is significant in understanding how wind influences landforms and contributes to landscape evolution.
Yedoma deposits: Yedoma deposits are a type of permafrost accumulation characterized by a mix of ice and organic-rich sediments found primarily in Siberia and parts of Alaska. These deposits play a crucial role in understanding climate change because they contain ancient carbon and provide insights into past environmental conditions, as well as influencing the landscape through processes such as thermokarst and sediment flux.