Lines of dowels originally inserted vertically to depths of 100 and 200 mm in generally fine grained soil across sorted circles were repeatedly surveyed over a 3 year period. Measurements of dowel heave, lean, and lateral displacement provided evidence of circle activity. They suggest that the cumulative soil displacement was radial and that its velocity near the surface increased linearly from zero at the center of a circle to a maximum at the stony border. This permits an estimate of the minimum age of circles. Radial displacement decreased with depth and was probably negligible below an average depth of about 100 mm. Although this displacement pattern supports the soil-circulation hypothesis for well-developed sorted circles, the data also suggest some limitations.

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