A reoccurring phenomenon
The Rosshag Sinkhole is the most recent of several cracks in the shell limestone around the Göschweiler-Reiselfingen region. These sinkhole occurrences on shell limestone are always connected to subterranean cave systems. They are caused by naturally acidic rains which dissolve the limestone by entering the rocks through crevasses until they meet a water-resistant layer (e.g. clay) upon which they drain off underground, causing progressive corrosion. This leads to irregular, hollow, tunnel-like formations with narrowing cross sections at the top. Further corrosion causes the rooves of these tunnels to continue growing upwards until they are on the brink of collapse. An initial geological analysis of the sinkhole showed that it was caused by an underground cavity with a roof that reached a height of 8 m before it collapsed. The bottom of this underground cave reached 60 - 70 m below the surface, right into the middle shell limestone with its highly soluble gypsum layers. Perhaps this makes it partially responsible for the high occurrence of sinkholes in the Göschweiler-Reiselfingen region. Dr Dieter Heim and Dr Dieter Mellert, Göschweiler