Colliery and surface hazards through coal-pyrite oxidation (Pennsylvanian Sydney Coalfield, Nova Scotia, Canada)

Based on these studies, and on direct observations over several years, a conceptual model of roof-rock instability is proposed. This model explains rock falls in tunnels (slopes) during once-operating coal mines (short-term hazard), as well as surface subsidence in land areas undermined long ago by room-and-pillar methods in the Sydney Coalfield (long-term hazard). The model invites testing in other Pennsylvanian coalfields that have similar geochemical conditions and employ similar mining methods.