A large sinkhole in the Verchnekamsky potash basin in the urals

One of the world’s largest sinkholes (80 m long, 40 m wide and 200 m deep) developed in July 1986 as a result of potash mining 425–435 m below the land surface. The depth of the 3rd Bereznikovsky potash mine did not contribute to the collapse, and in fact, the sinkhole occurred in a location where the depth of the mine and the nature of the overburden were considered to be very favorable for mining. The nature and cause of the mine flooding and the collpase have been investigated and are elucidated. This case study is an example of how dangerous flooding can be in evaporite strata, even in deposits where geological conditions of mining appear to be very favorable.