Solifluction: This is the slow downslope flow of saturated soil. During summer, the active layer thaws but the underlying permafrost remains impermeable, preventing drainage; the water-logged soil becomes fluid and moves under gravity, forming solifluction lobes.
Frost Creep: A variation of mass movement where frost heave lifts particles perpendicular to the slope, and subsequent thawing drops them vertically due to gravity. This results in a zig-zag downward migration of soil.
Nivation: A collective process involving freeze-thaw and meltwater erosion beneath snow patches. It hollows out the ground, eventually creating nivation hollows which may develop into cirques if glacial conditions take over.
| Feature | Description | Formation Mechanism |
|---|---|---|
| Patterned Ground | Geometric shapes like polygons or circles | Frost heave sorts stones by size; larger stones move to the edges. |
| Stone Stripes | Parallel lines of stones on slopes | Gravity elongates polygons into stripes as they move downhill. |
| Closed-System Pingo | Found in flat lake beds | Trapped water in a former lake bed freezes and pushes the ground up. |
| Open-System Pingo | Found on valley slopes | Groundwater from higher elevations flows under pressure and freezes. |
Identify the Trigger: When asked about periglacial movement, always check if the process is driven by gravity (solifluction) or expansion (frost heave).
Distinguish from Glacial: Remember that periglacial landforms are created by ground ice and freeze-thaw, whereas glacial landforms are created by the movement of surface ice masses.
Scale and Time: Emphasize that these features are cyclical. A single freeze-thaw cycle does not create a pingo; it requires centuries of consistent thermal conditions.
Common Error: Do not confuse 'permafrost' with 'glacier'. Permafrost is frozen ground (soil/rock), not a moving body of ice on the surface.
