Glaciated Landscapes: Periglacial Landforms Flashcards
How are solifluction lobes and sheets formed?
Solifluction (movement of the active layer) downslope forms rounded terraces and sheets of soil
How are pingos (in general) formed?
Groundwater freezing forms an ice lens, which forms a dome of up to 500m in diameter and 50m in height
How do closed-system/hydrostatic/Mackenzie pingos form?
A frozen lake with sediment of the floor insulates the ground below against the cold, which allows talik to exist. The frozen lake then forms into an ice lens as the permafrost around advances, increasing in size due to hydrostatic pressure, which pushes the lake sediment up. Cracks can also appear on the surface due to ground swelling
How do open-system/hydraulic/East Greenland pingos form?
Water trapped between the permafrost and freezing active layer forms an ice lens, which rises and grows in size due to hydraulic pressure, which causes the soil above to expand and rise. Cracks can also appear on the surface due to ground swelling
How do ognips form?
Both types of pingos can collapse when they become too large, as ground cracks expose the ice lens to the sun or the temperature rises, which causes melting and eventual collapse. This leaves the ruptured pingo as a rampart (which is prone to solifluction) around a depression, which can fill with water forming a lake
How is patterned ground formed?
Large stones are pushed to the surface by frost heave, creating domes. The stones then move radially after reaching the surface, creating shapes made up of lines of rocks which make up stone polygons, garlands and stripes
On what angle are stone garlands formed?
3-5 degrees
How large are stone polygons normally?
1-2m
On what angle are stone stripes formed?
6 degrees and over
What’s the difference between stone polygons, stone garlands and stone stripes?
Stone polygons are the patterns formed on flat ground, stone garlands on slopes of 3-5 degrees, and stone stripes on slopes of 6 degrees or more
