Periglacial Processes + Landforms Flashcards
What do periglacial areas contain?
Permafrost- permanently frozen ground with a top layer that can melt in summer (ACTIVE LAYER)
What is continuous permafrost?
All the ground is frozen
What is discontinuous permafrost?
Only patches of the ground are frozen
What’s sporadic permafrost?
The annual temp is around freezing point and permafrost only occurs in isolated spots
What does the temperature have to be like for discontinuous permafrost to form?
Below 0° for at least two years
What does the temperature have to be like for continuous permafrost to form?
Mean annual temp must be below -5°
What is solifluction?
As the layer of permafrost is impermeable if the temp gets above 0° in summer the active layer melts but the water can’t go anywhere
-meaning the active layer gets waterlogged and will easily flow -SOLIFLUCTION
How do ice wedges form?
When the temperature drops low in the wings the group contracts and cracks from in the permafrost
- in the warmer month the increase in temp cause the active layer to thaw and meltwater to seep into cracks
- the permafrost layer is still frozen so water will freeze in the cracks
What is frost heave?
When water in the ground makes humps on the surface
How is frost heave formed?
When the active layer freezes the ice forms a lens shape
- in the fine grained soil the ice lifts up the surface layers of the soil
- ice lenses also form underneath stones due to them kissing heat quacking and faster than the surrounding soil
What happens as the ice lens expands in frost heave?
They push stones upwards toward the surface of the ground and eventually the stones rise above the surface of the ground
What is patterned ground?
When stones get pushed to the surface by frost heave,once they reach the surface they roll down to the edges of the mounds that have formed
What is nivation?
When the snow gets into a hollow in the ground and increases the size of the hollow
- as the temp is periglacial freezing and thawing happens
- every time the ice freezes it expands,leading to frost shattering eventually breaking off parts of the rock at the base
What happens to material in nivation?
Material gets carried away by meltwater and eventually the hollow becomes deeper and wider
-this is the beginning of a corrie
What are pingos?
Ice filled periglacial hills
-they are conical hills with a core of ice that can be as large as 80m high and 500m wide
What are then two types of pingos?
Open & closed systems
What are open system pingos?
These form where there discontinuous permafrost
- the groundwater is forced up through the gaps between the areas of permafrost
- water collects together and freezes forming a core of ice that pushes the ground upwards
What are closed systems pingos?
Form in areas of continuous permafrost where there’s a lake at the surface
- the lake insulates the ground so the area beneath remains frozen
- When the lake fries up and the ground is no longer insulated,permafrost advance the area of the area of unfrozen ground
What happens to the water that collects in the unfrozen ground of a closed pingo?
The water freezes to create the core of ice that pushes the ground up
