2.3 Flashcards
What are the different types of permafrost?
Continuous permafrost - permanently frozen ground
Discontinuous permafrost - frozen ground with unfrozen ground (talik) likely to be present.
Where is continuous permafrost found?
At high latitudes. This means low temperatures. This means thick permafrost and thin active layer
Where is discontinuous permafrost found?
Discontinuous permafrost is found at areas at lower latitudes. This will lead to warmer temperatures, which will lead to to a shallower permafrost depth and a thicker active layer.
What factors affect the distribution and character of permafrost?
- Climate
- Proximity to water (e.g. lakes)
- Slope orientation
- Character of ground surface
How does climate influence the distribution of permafrost?
Temperature and amount of moisture available, determines the depth and extent of permafrost.
How does proximity to water affect distribution of permafrost?
If an area is close to a lake, it can act as an insulator to the ground beneath. More insulation leads to less permafrost.
How does slope orientation influence distribution of permafrost?
Slopes that are north facing are less likely to receive solar radiation and therefore likely to be of a lower temperature. As a result the depth of permafrost with likely be larger.
How will the character of ground surface influence the distribution of permafrost?
If an area is of light nature - e.g. snow cover will lead to the albedo effect taking place lowering the temperature.
Areas of a dark nature - bare rock is likely to absorb more radiation - as a result the temperatures will be higher leading to less permafrost.
Describe the formation of stone polygons
Step 1: Water freezes when it comes into contact with rocks, as it has a lower temperature than the soil.
Step 2: This causes the formation of ice lenses.
Step 3: When water freezes it expands by 9%. This causes the ice lenses to heave the rocks above them, causing them to dislocate the ground above it. The rocks then reach the surface. This is a continuous process, which occurs in cycles to eventually push the rocks to the surface creating a dome shape.
Describe what happens once stone polygons have reached the surface
The stones reach the surface. Due to the gradient of the land now created, the largest rocks are pulled by gravity to migrate outwards, which form circles. The smaller rocks are then removed by wind of meltwater.
Describe the process of nivation.
- Takes place on north facing slopes and high altitudes.
- Snow can get into a hollow in the ground.
- Freeze thaw weathering can occur, disintegrating the underlying rock.
- Some of the snow turns to meltwater in the spring. Thus carries away debris.
- Over a long period of time, this process repeats creating a larger hollow.
- This is called nivation, forming nivation hollows.
