Periglacial landscapes and landforms Flashcards
How is patterned ground formed?
Freeze thaw weathering causes ice lenses in the permafrost.
Capillary action causes water to draws to ice lenses allowing the expansion of the lens. Stones around the ice lens are pushed up. Larger stones roll downhill from their weight, finer sediments fill the space around.rocks. This makes the rocks appear to be a flat surface with shapes or lines.
How are ice wedges formed?
Water infiltrates small cracks and expands when it freezes during the winter. The repeated process causes the crack to expand and leave large ice wedges in the ground.
How do open pingos form?
It forms in discontinuous permafrost when water moves through unfrozen ground in the permafrost. Capillary action causes the water to group together and then freeze in the colder winter months which creates water lenses.
The ice lens continues to grow and pushes unfrozen ground up, creating a mound.
How do closed pingos form?
Closed pingos form in continuous permafrost.
Under a lake permafrost is insulated and melts. The lake eventually drys up or freezes leaving a patch of unfrozen ground beneath.
Capillary action happens and creates an ice lens.
As the temperatures drop the permafrost advances and frost heaves the unfrozen ground up, creating a mound.
How do terracettes form?
It is not wholly known or agreed upon but geographers believe that:
- Frost heave pushes the soil up when it would usually go downhill due to the process of creep.
- Vegetation stops soil from falling so it forms a step shape.
How do solifluction lobes form?
When the active layer thaws and solifluction occurs, tongue shaped loves of soil fall down a slope.
What is thermokarst?
Boggy wetlands caused from permafrost melting.
Any ice lenses within the ground would melt and collapse leaving holes in the ground.
These holes may fill with meltwater.
