In 2013, a sinkhole 200 feet across and 90 feet deep appeared in Wallace County in western Kansas. Some people speculated that excessive pumping of water from the Ogallala aquifer may have contributed to the collapse, but the KGS determined that natural dissolution of underground halite (commonly known as rock salt) was the more likely cause. Under this theory, groundwater seeped through fractures in layers of Cretaceous chalk and slowly dissolved the 200-foot-thick bed of halite 2,000 feet beneath the surface, eventually creating a substantial void. When the rock above could no longer sustain the weight, everything from the surface down suddenly collapsed.
In other parts of the state where more is known about the subsurface, most notably around Hutchinson where salt has been mined for decades, catastrophic sinks have been more definitively linked to the dissolution of underground salt, gypsum, or other evaporites.
The Wallace County sinkhole is not unique. Several historical collapses, including the Old Maid sinkhole, have been documented in Wallace County alone, and sinkholes have been reported in at least a quarter of the 105 Kansas counties.