Coal mining in Nova Scotia has taken place since the 1600s. This activity has left many areas affected by historical underground coal mining. Such undermined lands may be affected by events known as mine subsidence. There are two types of subsidence: sinkhole (i.e. open holes) and sag or trough (i.e. shallow, saucer-shaped depressions). Subsidence effects on surface development depend on the depth and size of the mining excavation (length, width & height), type of rock and geological structure, groundwater conditions, as well as the type, construction and condition of surface structures. Subsidence events can occur many years after mining has ceased. It is very difficult to predict where and when these events will occur because of the unknown details and condition of the underground workings. Despite these limitations, general guidelines and generic precautionary and remedial approaches are available.
Mine subsidence can cause conditions that are very hazardous. Do not enter any area that is suspicious or that has been designated or fenced off as a subsidence hazard area. If you suspect mine subsidence on your land please call your local planning office.