GL 5 Flashcards
What is a periglacial landscape?
Landscape that undergoes seasonal freezing and thawing
What is permafrost
Ground that remains frozen for 2 or more consecutive years
Where is permafrost found
Tundra environment, and areas on the fringes of past and present glacial areas, high latitudes and altitudes
What are some factors that impact permafrost
Proximity to water bodies - Land in contact with bodies will remain unfrozen
Slope angle and orientation - influence amount of solar radiation received - active layer is higher depth on south facing slopes
What surface is made from - absorb more/less solar radiation
Vegetation cover - insulates ground, defends from sun’s rays, intercepts snowfall (encourages permafrost)
presence of snow - Slows freezing and thawing
What percentage of the Earth’s landscape contains permafrost
25%
What is the mean annual temperature needed for permafrost to occur?
-2 degrees celcius
How deep can permafrost be?
up to 1500m
What is the active layer
Thin layer of soil on top of permafrost that can thaw, plants grow here
Why is there more permafrost at the poles
at poles, there is lower temperature, as less of the sun’s insolation reaches poles
What is continuous permafrost?
Forms in the colder areas of the world, where temperatures are below -6 degrees Celsius, extending down hundreds of meters
What is sporadic permafrost?
Like continuous but fragmented and thinner
What is discontinuous permafrost?
Occurs at margins of periglacial environments and is fragmented and only a few meters thick
Why is the melting of permafrost so detrimental to climate change
Permafrost contains lots of methane, due to dead organisms being broken down during anabolic respiration the melting of which releases it.
What are some negative impacts of permafrost melting?
What percentage of animals live in permafrost environments
Half
If permafrost melts, how many miles of habitats will be lost
9 million miles
What makes methane worse for global warming then carbon dioxide
Methane is 25x more potent, meaning high global warming potential
What is cryoturbation
Ground is mixed and broken (involutions) up by frost shattering
What is segregated ice, how is it formed
forms in active layer, when freezing rates are unequal, due to capillary movement, when water moves up, towards freezing front
How is pore ice formed?
Develops in pore space between sediment particle
What is needle ice?
narrow ice slivers, up to several cm long
How is needle ice formed?
form in moist soils overnight
What is an ice lenses
cause up doming of ground (earth hummocks) during frost heave, up to several meters in high and diameter
Explain the formation of an ice lenses
bodies of ice are formed when moisture, mixed within soil or rock, accumulates in a localised zone, because rates of freezing are unequal in the active layer
What are ice wedges
downward narrowing lens, up to 3 meters wide and extend below ground up to 10 meter
Explain the formation of ice wedges
In winter, ice is in the crack, in summer, this ice thaws, in the second winter Water freezes and expands by 9%, forming layer, annual freezing and thawing causes expansion, ridges form as sediment is pushed off.
Explain the formation of ice wedge polygons
Ground contracts and cracks in winter, in summer crack fill with water, this freezes and keeps the cracks open
What is patterned ground?
stones arranged in geometric shapes, (stripes, circles and polygons)
Explain why stones move to the surface in periglacial environments?
Ground will freeze downwards, stones are good conductors of heat, so when temperatures drop and expanding ground begins to lift the stone. Small amounts of moisture beneath the stone freeze and turn into ice, expanding by 9%. Cryostatic pressure, raises the stone (frost heave). Ice thaws, wet sediment slumps into gap beneath the stone, after many repetitions, stones break through the surface.
What happens after stones break through the surface
Sones roll to the base of mound, steep hills, cause stripes, gradual gradients form polygons or circles
Why are patterns formed in patterned ground?
Different patterns are formed by the topography of the ground (rocks roll)
What is a pingo
Ice cored hill, height of 3 to 70m, diameter of 30 to 1000m.
What is a closed system, what is an open system
Closed - no transfer in or out
Open - transfer in or out
What is the largest pingo
Kadleroshilik Pingo, Alaska, 54m high
Where are closed system pingos found, where are open system pingos found
Closed - continuous permafrost
Open - discontinuous permafrost
Explain stage 1 open system pingo formation
Groundwater is confined beneath the permafrost. It finds a weakness in the permafrost and rises due to artesian pressure. As the water rises, it cools and freezes, if it reaches the surface by summer it may form a spring.
Explain stage 2 of open system pingo
During winter the rising water freezes before reaching the active layer, forming an ice lens. As more groundwater rises from below the permafrost, it grows, displacing the overlying sediment, forming a domed ice hill, known as an open system pingo
Explain stage 1 of closed system pingo
Lakes form withing active layer during summer months, during winter this begins to freeze. Unfrozen water and lake sediment insulate the underlying ground, preventing ground from freezing (talik)
Explain stage 2 of a closed system pingo
During cold, permafrost advances, encroach on Talik, liquid water freezes, becoming an ice lens. Ice lens grows, exerting cryostatic pressure, displacing overlying lake, sediment at bottom of lake now covers top.
What is a thermokarst landscape
irregular surfaces, marshy hollows and depressions
What is a thermokarst landscape formed by
Permafrost thawing due to warming climate.
What is solifluction, what is this caused by
Wet, saturated active layer moves slowly downhill, due to gravity
What is beaded draining in a thermokaust landscape
Due to unequal thawing patterns of active layer, leading to small pools of meltwater, interlocked by small streams
What are thermokaust lakes
Formed in a depression by meltwater from thawing permafrost
What is one cause of thermokaust lakes
Pingo collapse, water cannot percolate downwards into impermeable permafrost
Explain pingo collapse
Temperatures warm, increased meltwater, ice lens begins to be exposed, solifluction of sediment in both directions atop the ice lens occurs, causing a depression when ice lens is reduced.
What is the Batagay crater, where is it, what is happening to it
In russia, permafrost is melting, forming a crater
What is causing the batagay crater?
Global warming - artic warms 2x faster (artic amplification)
South facing slopes experiencing most melting
mass solifluction
What proportion of Russia has permafrost?
Over half
What is the problem with melting permafrost in Russia?
In villages like bataguy, the ground gives way and buildings collapse
How much is the bataguy crater increasing each year?
10-15cm
What is a block field
surface covered by large angular rocks, product of freeze thaw on a flat plateau
What is an example of a block field
Glyder Fawr - Nant Ffrancon valley
What is a scree slope, example
An accumulation of freeze thawed weathered rocks at the base of a cliff, Nant Ffrancon valley
Explain the formation of a scree slope
Freeze thaw occurs at the top of a drop, this reduces slope angle, overtime weathered rock from the top accumulates at the base
Explain the formation of a protalus Rampart, Example
Same formation as a scree slope, but with added ice in the middle, this causes rocks to build up around the ice. When the ice melts, a bulge in a slope is left. Cwm Idwal
What type of mass movement is saturated soil moving due to gravity
Soliflucation
Outline the process of solifluction
Active layer thaws, permafrost remains frozen, surface layer becomes water logged because water cannot infiltrate and percolate into permafrost.
Explain frost creep
On slopes, during summer, the active layer thaws, in winter, when this freezes, it expands outwards (frost heave), during the next summer, particles drop vertically, forming terracettes
Explain solifluction sheets and lobes
Solifluction occurs at different rates due to the topography of the land, causing lobes and sheets to be formed
Where can scree slopes, protalus ramparts, solifluction lobes, terracettes be found
Nant Ffrancon valley
Explain the formation of dry valleys in periglacial environments
Develop in areas of permeable rock in active layer, surrounded by permafrost, When ice masses retreat, meltwater erodes and deepens river ‘V’ shaped valleys, when permafrost has melted, water can infiltrate, reducing surface run off and leaving river valley dry
Give an example of a dry valley
Yorkshire dales
What is Loess deposits
Fine rock debris transported (deflation) and deposited by winds, creating flat plateaus
Explain Loess deposits
derived from glacial abrasion, which is transported by meltwater to sandurs, during colder months, large parts of the sandur will dry out, exposed to strong winds
How can wind impact of glacial depris
Loess deposit
Abrasion
