Glaciated Landscapes SG6 Flashcards
Define Periglacial
Areas with permafrost mainly in high latitude locations with temperatures fluctuating around 0 degrees C
What % of Alaska is periglacial?
90%
What % of the earth’s surface is periglacial?
25%
Define Permafrost
Ground that remains frozen for at least two consecutive years overlain by an active layer
Define Active Layer
Thawed permafrost when temperatures exceed 0 degrees C
Define Talik
Unfrozen ground, normal/loose soil
What are the three types of permafrost?
Continuous, Discontinuous, Sporadic
What is the depths of the three types of permafrost?
Continuous - 396m
Discontinuous - 45m
Sporadic - 12m
What is the depths of the active layers above the three types of permafrost?
Continuous - 0.5m
Discontinuous - 1-1.5m
Sporadic - 1.5-3m
Define Solifluction
The upper layer of soil in the active layer undergoes seasonal thawing. Water can’t drain away due to the impermeable permafrost below so active layer may begin to move downslope when saturated
What angle are the slopes at on which solifluction takes place?
2 degrees
Explain the process of freeze-thaw weathering?
Water enters cracks in the rock. When temps are below 0 degrees C the water freezes and expands by 9% putting pressure on the rock causing it to crack further. It then thaws when temps increase slightly
What are the five geomorphic processes in periglacial landscapes?
Solifluction, Weathering, Nivation, Ground Ice, Frost Heave
Define Nivation
A collection of geomorphic processes which can occur under a permanent snow patch high up in the mountain
Define Ground Ice
A generic term which includes ice lenses and ice needles
Define Ice Lens
An accumulation of ice beneath the surface which forms a lens shape parallel to the ground surface and the thickening of the ice at its centre causes the ground to heave upwards
Define Ice Needles
A needle-like column ice column which lifts or pushes away small soil particles
Are ice lenses or needles more likely to form in areas which experience lower temperatures for longer periods of time?
Ice Lenses
Define Frost Heave
A subsurface process that leads to vertical sorting of material in the active layer
Define Specific Heat Capacity
The amount of heat required to raise the temperature of a given mass of a substance by one degree C
A substance with a low heat capacity will…
Heat and cool quickly
A substance with a high heat capacity will…
Heat and cool slowly
Define Patterned Ground
The collective term for a number of fairly small scale features of periglacial landscapes including stone polygons and stone stripes
What angle are the slopes which stone polygons form on?
Less than 6 degrees
What angle are the slopes which stone stripes form on?
More than 6 degrees
Define Pingos
Rounded ice cored hills that can be as much as 90m in height and 800m in diameter
At what rate do pingos grow?
A couple of cm/year
What are the two types of pingo?
Open system and closed system
Define Artesian Pressure
When groundwater is put under enough pressure it can be lifted up to a higher level than the surface of the ground
Define Ognip
The remains of a collapsed pingo forming a depression surrounded by circular earth ramparts
Define Thermokarst
Used to refer to areas of hummocky, irregular ground interposed by waterlogged depressions created as ground ice thaws. Depressions fill with water to form shallow lakes less than 5m deep and 1-km wide
Define Ice Wedge Polygon
A crack in the ground formed by a narrow or thin piece of ice that measures up to 3-4m in length at ground level and extends downwards into the ground up to several meters
How long is the Trans-Alaskan Pipeline (TAPs)?
800 miles log
What are four reasons the oil industry is important to Alaska?
Resource availability, Demand for oil, US energy security, Benefits for Alaska
What is the depth of the continuous permafrost at Prudhoe Bay?
660m
What is the depth of the active layer at Prudhoe Bay?
0.5m
What are four consequences of changes on the landscape?
Increased solifluction, Development of thermokarst landscapes, Formation of Alases, Degradation of Ice Wedge Polygons
Define Alas
A flat floored, steep sided depression ranging from 5-50m in depth and 100m-15km in length
