Shallow mineworkings are the abandoned mining tunnels in coal seams and metalliferous veins which lie at a depth which might cause surface subsidence if the roof of open workings collapse.
The roof of coal workings is rock, either shale or sandstone, which may deteriorate with time. Only relatively recent workings or access drifts would have temporary supports such as timber pit props in place.
Lead veins were commonly worked upto rockhead, leaving only clay spanning the vertical voids where the ore has been extracted.
These shallow workings mostly pre-date the Mines Act of 1872 which required mine owners to keep plans of their workings and therefore the only method of locating the workings is by physical investigation. Very shallow workings, for example at outcrop, can be investigated by excavation but for most sites drilling is required and the skill and experience of the driller is paramount if a geologist is not in attendance.