Subsidence

The sinking, cracking or sudden collapse of the ground surface caused by the failure or movement of underground workings beneath it — ranging from a slow, shallow sag spread across a wide area to a sudden, narrow 'crown hole' opening without warning.

Historical usage

A recognised hazard wherever shallow underground workings lay beneath land still in use — farmland, roads, railways, and, in later 20th-century Britain, whole streets of housing above old coalfields. Concern over unrecorded or poorly mapped historic workings has remained a live planning issue long after the mines themselves closed, since a void driven and abandoned a century or more ago can still collapse to the surface without warning.

How it worked

Where pillars or unsupported roof spans are left to carry the weight of the ground above indefinitely, they can weaken, crack or crush over time, especially once water reaches the void; the roof then fails and the collapse works its way upward through the overlying rock and soil until it finally reaches the surface — either as a sudden, steep-sided 'crown hole' directly above old shallow workings and roadway junctions, or as a broader, gradual subsidence trough where a wide area has been worked out, as beneath a longwall coal panel.

Risks & limitations

Because subsidence can lag mine abandonment by decades, it remains a genuine hazard long after a site itself is forgotten: a crown hole can open beneath a road, a garden or a railway line with no surface sign the ground beneath was ever worked, as it did without warning at Lindal Moor in 1892 and again in 1893.

Regional variation

Coalfield subsidence, spread across wide longwall-worked panels, tends to produce a broad, gradual trough; subsidence over shallower metal-mine or salt-mine workings, and over old shaft and roadway junctions generally, is more often the sudden, localised crown-hole type.

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Combe Down Stone Mines — Somerset (well documented example)
  The mine's own recorded history explicitly describes roof falls causing subsidence above ground, confirmed by a 1994 survey.
• Lindal Moor — Cumbria (well documented example)
  The mine's own recorded summary, history and surface remains explicitly describe the 1892 subsidence that swallowed a locomotive, and further subsidence in 1893.
• Oakeley Quarry — Gwynedd (well documented example)
  The mine's own recorded current condition explicitly describes closure following the discovery of subsidence.
• Winsford Rock Salt Mine — Cheshire (well documented example)
  The mine's own recorded geology explicitly describes serious ground subsidence caused by salt mining near Northwich.

Sources

1. (secondary) A sinking feeling | Subsidence and old mine workings: underground dangers — isurv
2. (secondary) Chapter 11: Coal mining subsidence in the UK — Geological Society, London, Engineering Geology Special Publications

Record created: 24 August 2026 · Last researched: 24 August 2026