Land subsidence caused by solution mining in the Mogilno salt dome

Occurrence of land surface subsidence is a result of rock salt extraction. The process is observed by geodetic measurements. On the Palędzie I salt mining field, such measurements are conducted every five years. The most recent series of measurements was carried out in 2009. The analysis of land levelling results indicated that a twin-centre subsidence is still being formed above the salt mining area. Its maximum load on the SW side of the salt dome exceeded −100 mm in 1986–2009. The second subsidence centre behind the NE edge pillar is 50% smaller than the first one. Along with the extraction moving up to shallower areas of the salt bed, the rate of land surface subsidence is increasing, with the decreasing perimeter of the depression. The indicators that describe the land surface subsidence – vertical displacement of benchmarks and the caverns volume – are presented on the function of time and a parameter, determining the distance from the measurement point to the exploitation field edges