Periglacial processes & Landforms Flashcards
What does ‘Periglacial’ describe?
‘Periglacial’ describes a landscape that undergoes seasonal freezing and thawing, typically on the fringes of past and present glaciated regions.
These landscapes produce unique landforms governed by specific depositional and erosional processes.
What is freeze-thaw weathering?
Freeze-thaw weathering (frost action) is the process when water enters cracks in the rock, freezes, and expands by about 9% in volume, causing rock to fracture.
This leads to the formation of frost-shattered debris or scree.
What is solifluction?
Solifluction (Soil Flow) is the gradual movement of a mass down a slope related to freeze-thaw activity, particularly in regions with permafrost.
It reaches its maximum potential in late spring and summer.
What causes frost heaving?
Frost heaving is caused by the upwards swelling of soil during freezing conditions due to the presence of ice growing towards the surface.
It occurs from the freezing front penetrating into the soil.
Define permafrost.
Permafrost is permanently frozen ground that remains continuously below 0 °C for two or more years.
It restricts plant root growth and affects drainage.
What is continuous permafrost?
Continuous permafrost forms at mean annual air temperatures below -5 °C and is laterally continuous across large areas.
Found in polar regions such as most of Alaska and Siberia.
What characterizes discontinuous permafrost?
Discontinuous permafrost forms where the mean annual air temperature is between -2 and -4 °C, allowing permafrost to persist in 50 to 90 percent of the landscape.
Typically occurs around the edges of polar regions.
What is sporadic permafrost?
Sporadic permafrost is present where 10 to <50 percent of the landscape is underlain by permafrost and mean annual air temperature is between 0 and -2 °C.
Found in high mountain regions of cooler climates.
What defines isolated permafrost?
Isolated permafrost is where less than 10 percent of the landscape is underlain by permafrost.
This indicates very limited permafrost presence.
What are pingos?
Pingos are intrapermafrost ice-cored hills, 3–70 m high and 30–1,000 m in diameter.
They are typically conical in shape and grow only in permafrost environments.
How are closed system pingos formed?
Closed system pingos are formed as a result of hydrostatic pressure within the core due to water, occurring in regions of continuous permafrost.
They are found in flat, poorly drained areas.
What characterizes hydraulic (open-system) pingos?
Hydraulic (open-system) pingos are formed by doming of frozen ground caused by groundwater that moves downslope through taliks.
This groundwater freezes on the pingo surface.
Define patterned ground.
Patterned ground is a surface feature consisting of repeated geometric patterns in the soil or rock, often in the form of polygons, circles, or stripes.
Examples include sorted polygons and frost ripples.
What is thermokarst?
Thermokarst is an erosional process unique to permafrost with excess ice, resulting from the thawing of ice-rich permafrost and/or melting of massive ice.
It creates depressions, ponds, or wetlands.
