Periglacial Shite Flashcards
(25 cards)
What are the 3 types of permafrost?
Continuous
Discontinuous
Sporadic
What is continuous permafrost?
Found in coldest regions
Little thawing in Summer
-5 to -50 degrees
Up to 700m in Canada
What is discontinuous permafrost?
Slightly warmer conditions
Breaks in permafrost under lakes, rivers, sea etc
20-30m avg
-1.5 to -5 degrees
What is sporadic permafrost?
Mean annual temp. just below freezing
Permafrost occurs in isolated spots
Local climate cold enough to prevent complete thawing
0 to -1.5 degrees
What is permafrost?
Layer of soil, sediment, or rock below surface remains permanently frozen
What is the active layer?
Topsoil in permafrost environments
Thaws in summer
Freezes in winter
Which factors influence prescence of permafrost?
Rock + soil types (Depth)
Vegetation (Insulation)
Snow cover
Slope angle (Solar radiation)
Proximity to water bodies
List periglacial processes
Freeze thaw
Nivation
Frost heave
Groundwater freezing
Solifluction
Meltwater erosion
List periglacial landforms
Nivation hollows
Patterned ground
Ice wedges
Pingos
Solifluction lobes
Braiding
Scree
Loess
Which landform does freeze thaw create?
Scree
Which landform does nivation create?
Nivation Hollow
Which landform does frost heave create?
Patterned ground
Some pingos
Which landform does groundwater freezing create?
Pingos
Which landform does solifluction create?
Solifluction lobes
Which landform does meltwater erosion create?
Braiding
How is a nivation hollow created?
Snow falls into hollow/depression
Protected from wind + sun
Compaction by further snowfall
Underlying rocks weakened + eroded
How is a solifluction lobe created?
Active layer thaws
Meltwater reduces friction between soil particles
AL moves downslope
Rounded tongue like features form terraces in valley
What is gelifluction?
Combination of solifluction with frost heave and permafrost
How is patterned ground created?
AL freezes, ice lenses develop
Soil volume rises + forced upwards
Frost heave - fine grain soil expands unevenly
Stones heat up faster than ground, cool + expand when ground freezes
Freeze thaw, crystals heave rocks upwards
How is an ice lens created?
Soil moisture becomes free
Lens develops
Fed by water from capillary action + movement through frost susceptible soil
Lens expands, land lifts + heaves
What are the 2 types of pingo?
Open system
Closed system
How is a pingo formed?
Groundwater freezes into ice lens
Lens trapped within layers of land
Lens forces overlying land + sediments upwards
What is the difference between the 2 types of pingo?
OS - Water able to seep through permafrost
CS - Water unable to seep through frozen ground
How is an ognip created?
Pingo grows overly large
Lens exposed
Lens melts
Pingo collapses
