10.3.1 Solifluction

It produces distinctive lobes on hill slopes. These occur in areas where the soil remains saturated with water for long period of time. Solifluction, also known as soil fluction, is a type of landslide where waterlogged sediment moves slowly downslope, over impermeable material. It can occur on slopes as shallow as 0.5 degrees at a rate of between 0.5 and 15 cm per year. It occurs in periglacial environments where melting during the warm season leads to water saturation in the thawed surface material (active layer), causing a form of downslope flow to occur. A Solifluction lobe is a type of slope failure where sediments form a tongue-shaped feature due to differential downhill flow rates (figure 8).  Where the underlying ground is permanently frozen (permafrost), the process is often called gelifluction.

 

Figure 8: Rock and soil moves vertically back to the surface in Solifluction