How does solifluction move soil on slopes above permafrost?

Solifluction is the slow, downslope flow of water-saturated soil, a process driven by the presence of permafrost. Because permafrost is impermeable to water, it prevents downward drainage, causing the overlying "active layer" of soil to become oversaturated and mobile during the summer thaw.213

This movement occurs through the following mechanisms:

• Gravity and Saturation: Once the active layer becomes waterlogged, it loses stability and slides downslope under the influence of gravity.234
• Frost Action: The process is facilitated by the freeze-thaw cycle, which weakens and opens the soil structure, making it more susceptible to flow.231
• Mass Transport: The material moves in a semifluid state, often forming distinct solifluction lobes or terraces. This mass transport can occur even on low-angle slopes, resulting in smooth, concave landforms and the contortion of original soil stratifications.312

When this movement specifically involves the active layer of permafrost, it is sometimes referred to as gelifluction.4