During the late 1970s and early 1980s, John Bell of NBMG studied the subsidence of Las Vegas Valley caused by groundwater extraction. Don Helm, a noted expert in the field of subsidence prediction, joined John and NBMG in late 1989. Removal of solid material from depth dominates the first, along with the subsequent bridging of overlying strata that weaken and eventually collapse into the excavation. Gradual compression of small pore spaces over a large region in response to interstitial fluid removal dominates the second cause, along with rearrangement of the particulate structure of sedimentary material that slowly reaches a sturdier, more compact configuration. Long Beach, Mexico City, and parts of the San Joaquin Valley have subsided as much as 9 meters due to fluid withdrawal.
Land subsidence is the surface expression of cumulative deformation at depth.
See also Nevada Bureau of Mines and Geology - Home Page. With links to additional pages. Land Reclamation Division, Illinois Department of Natural Resources. 2.To ensure the repair of damage to land and structures from mine subsidence caused by active underground mines. Subsidence in Las Vegas Valley.