How does solifluction occur in sub-Arctic regions?

In sub-Arctic and polar regions, solifluction occurs when the active layer of soil—the surface layer that thaws seasonally—becomes oversaturated with water. Because the underlying permafrost is impermeable, it prevents downward drainage, causing the waterlogged soil to become highly mobile.123

Driven by gravity, this saturated material flows downslope in a semifluid state. The process is significantly aided by frost action, which weakens and opens the soil structure, making it more susceptible to movement. This phenomenon typically manifests as lobelike or sheetlike flows, often resulting in the formation of solifluction terraces and lobes on slopes. Over time, this mass transport of material can produce smooth, concave slopes and may even cause rock slabs to stand on end.132