Solifluction

By: Dr. Pranab Kr. Das, Assistant Professor, Department of Geography, Sree Chaitanya College, Habra

Anderson (1906) first observed this solifluction in the mud glaciers of Bear Island, in the north Atlantic and stone river area in Falkland Island, south Atlantic. He concluded that it was a product of the slow movement of soil, saturated with glacial melt water in permafrost grounds due to gravity. Basically, it is a type of mass wasting which is very slow but faster than soil creep, a few inches per day. It is significantly slower than mud flow but more continuous; it is not confined to a channel as a mud flow usually is. Solifluction occurs under severe subarctic or alpine climate rather than under arid or semiarid climate as mud flow do. The permafrost regions are generally impermeable to water, soil overlying it may become oversaturated and slide downslope under the pull of gravity. Soil that has been opened and weakened by frost action is most susceptible. Eventually, it produces smooth, gentle, concave slopes.

Four conditions promote the solifluction – a) a good supply of water from the melting of snow and ground ice/glaciers; b) moderate to steep slope, relatively free of vegetation; c) permanently frozen surface or ground, d) rapid production of debris or rock waste by weathering.

Features of Solifluction:

Solifluction is the gravitative transfer of water-saturated soil down a steep slope.
It reaches its peak during the late spring and summer months when soils are saturated by thaw.
Solifluction can occur on slopes of less than 1 degree, but it is more common on slopes of 5 to 20 degrees.
Soil saturation normally reduces as water runs down the slope as runoff with more relief.
Solifluction is responsible for stratified and multi-layered slope deposits in many places. Example: the Colorado Front Range.
The circulation of water and the development of soils will be impacted by such deposits.
Increased pore pressures in saturated soils result in unstable circumstances due to a lack of friction and cohesiveness.

Deposits:

Slow periglacial solifluction deposits various particles ranging in size from clay to boulders in a poorly stratified and shorted.
A buried organic soil is often visible when stratification is being noticed.

Landforms:

Sometime soil catena is formed by developing different soil types in various heights in a mountain slope.
Slope failure may occured with lobes and sheets.
Due to differing downhill flow speeds, sediments create a tongue-shaped feature in solifluction lobes.
In contrast to solifluction lobes, solifluction sheet sediments travel more or less uniformly downslope, making them a less selective form of erosion.