What Is Solifluction?

When Waterlogged Soil Flows, Geologists Call It Solifluction

Solifluction is the name for the slow downhill flow of soil in arctic regions. It occurs slowly and is measured in millimeters or centimeters per year. It more or less uniformly affects the whole thickness of the soil rather than collecting in certain areas. It results from the complete waterlogging of sediment rather than short-lived episodes of saturation from storm runoff.

When Does Solifluction Occur?

Solifluction happens during the summer thaw when the water in the soil is trapped there by frozen permafrost beneath it. This waterlogged sludge moves downslope by gravity, helped along by freeze-and-thaw cycles that push the top of the soil outward from the slope (the mechanism of frost heave).

How Do Geologists Identify Solifluction?

The major sign of solifluction in the landscape is hillsides that have lobe-shaped slumps in them, similar to small, thin earthflows. Other signs include patterned ground, the name for various signs of order in the stones and soils of alpine landscapes.

A landscape affected by solifluction looks similar to the hummocky ground produced by extensive landsliding but it has a more fluid look, like melted ice cream or runny cake frosting. The signs may persist long after arctic conditions have changed, as in subarctic places that were once glaciated during the Pleistocene ice ages. Solifluction is considered a periglacial process, as it only requires chronic freezing conditions rather than the permanent presence of ice bodies.