Soil creep . Gradual downward movement of soil particles under the force of gravity. Causes fences to lean downhill and trees to have curved bases. Commonly associated with freeze-thaw activity. Freezing pushes surface particles outward, perpendicular to the slope.
Thawing allows the particles to drop vertically back to the surface.
Net downslope movement occurs. Gradual downward slumping of muddy, saturated soil, as it slides over the top of permanently frozen soil below. A common process only in tundra environments during their brief summer, when thawing creates a thin active layer over permafrost. C. Sudden mass wasting processes 1. Failure of slope along planar or curved surfaces.