Illustration of "erosion from below" shows how the fluctuation of the water table above and below the soil-rock contact develops cover collapse sinkholes. This is Figure 18 on pages 22 and 23 of Newton, John G., "Development of sinkholes resulting from man's activities in the eastern United States", US Geological Survey, 1987, CIRCULAR 968. Available at https://pubs.usgs.gov/circ/1987/0968/report.pdf

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