Coal Mine Subsidence near Sheridan, Wyoming. Surface subsidence effects above
abandoned coal mines 10 to 15 kilometers north of Sheridan. Subsidence
depressions and pits above the Old Monarch Mine in operation from 1904 to 1921.
Rectangular depressions, some of which are bounded by pits, are evident on the
right. Some of the pits are sealed at the bottom and provide sufficient
moisture to support trees (foreground). Overburden thickness is estimated to
be approximately 10 to 15 meters. The depressions occur where much of the coal
is removed and the remaining coal cannot support the weight of the overburden.
Pits at the margins of the depressions commonly are caused by piping failure
and the local flow of surface water to underground mines via subsidence cracks.
May 1978. Frontispiece A, Geological Survey Professional Paper 1164.
Digital File:dcr00006
ID. Dunrud, C.R. 6cp