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317; Lecture 18

TermDefinition
Periglacial An environment in the zone peripheral to glaciers OR near-glacial climate conditions
Periglaciation The geomorphic processes that result from repeated cycles of freezing and thawing (physical weathering)
Permafrost Perminantly frozen layer of soil/regolith that is bound together by ice & remains @ or below 0 degrees Celcius for @ least 2 years
Active layer Ground above permafrost which endures seasonal thawing during summer months
Talik A body of unfrozen ground occurring in permafrost
Continuous Permafrost underlying 90% of the landscape
Discontinuous Permafrost with a complex and patchy distribution that is underlying 50-90% of the landscape
Sporadic Permafrost preserved @ scattered sites, northfacing slopes or peat bogs where the peat insulates the permafrost & prevents melting
Pore/Interstitial Ice Ice forms in pore spaces & cements the soil matrix
Segregated ground ice Bodies of pure ice
Frost weathering & shattering A weathering process that creates angular rock debris
Frost Heaving & Thrusting A process where surface stones may be lifted when ice forms
Frost cracking A process where polygonal fracture patterns from expansion & contraction (heating & cooling, wetting & drying)
Solifluction The slow flowage of saturated regolith near the ground surface, either by freeze-thaw or liquefaction
Freeze-thaw Cycle A cycle in which temperatures fluctuate both above and below the freezing point of water
Liquefaction The process by which water-saturated sediment temporarily loses strength & acts as a fluid
Nivation The process of erosion of the ground beneath & @ the sides of a snow bank resulting from freezing & thawing
Frost creep Solifluction that moves material downslope during alternate freeze-thaw cycles
Gelifluction Regolith becomes saturated because water doesn't percolate through frozen permafrost, therefore collecting @ the surface, saturating the soil & creating high hydrostatic pressures which cause liquifaction
Ice wedges V-shaped masses of ground ice that penetrate the active layer & run down into the permafrost
Pingo A perennial frost mound consisting of a core of massive ice covered by soil and vegetation
Frost blisters Seasonal pingos formed in a single winter & melting over a single summer
Thermokarst Irregular terrain characterized by topographic depressions with hummocks (ridges) between them
Thaw lakes A body of water located in thermokarst depressions
Solifluction lobes Tongue-shaped features that form due to differential downhill flow rates
Solifluction sheets Areas of widespread solifluction lobes
Rock glaciers Lobes of frozen angular rock & fine debris mixed with interstitial/pore ice & ice lenses
Ice lens Bodies of ice formed when moisture, diffused within soil or rock, accumulates in a localized zone
Cryoplanation terraces A series of steps & benches that form by scarp retreat as the result of nivation
Richter slopes A landform where debris supply and removal are balanced
Permafrost degradation The deepening of the active layer (more soil ice melts every summer)
Created by: turboqueen