Gelifluction

Gelifluction is a periglacial process involving the downslope movement of soil and regolith that has been rendered capable of flowing by the presence of a saturated active layer. This active layer, which thaws seasonally above permafrost, becomes waterlogged due to poor drainage, especially if there is a significant amount of ice in the underlying permafrost. The water saturates the soil particles, reducing the internal friction and making the material behave like a viscous fluid.

The process is driven by gravity, causing the saturated soil to move slowly down even gentle slopes. Gelifluction is particularly common in Arctic, subarctic, and high-altitude regions where permafrost is present. Evidence of gelifluction can be observed in the landscape through features such as lobate debris spreads, sorted polygons, and terracettes, which are small, step-like formations on hillsides.

The rate of gelifluction can vary significantly depending on factors like the degree of soil saturation, the slope angle, the temperature fluctuations, and the texture of the soil. Fine-grained soils, such as clays and silts, are more prone to gelifluction than coarser materials like sands and gravels, as they retain more water and become more viscous when saturated. Understanding gelifluction is important for assessing the stability of slopes in periglacial environments and for predicting how these landscapes might respond to climate change.