Sinkholes are a documented and active geological concern across large areas of Texas. A sinkhole is a depression or hole in the ground surface created by the collapse of the overlying layer into a subterranean void. This collapse is driven by the dissolution of soluble bedrock, a process that happens naturally or can be accelerated by human activities. Texas’s diverse geology, ranging from limestone plateaus to deep salt beds, makes it particularly susceptible to these collapses.
Geological Causes of Texas Sinkholes
The primary natural mechanism for sinkhole formation in Texas is the process of dissolution, which creates what geologists call karst topography. This formation occurs when water, made slightly acidic by absorbing carbon dioxide from the atmosphere and soil, travels through underground rock layers. The resulting mild carbonic acid slowly dissolves certain types of rock, carving out caves, channels, and underground voids.
In Central Texas, the Edwards Plateau and Hill Country regions are characterized by thick layers of Cretaceous-age limestone and dolomite. These carbonate rocks are highly susceptible to dissolution by percolating rainwater, leading to an extensive network of underground conduits that form the Edwards Aquifer. As the bedrock dissolves, the overlying soil and rock lose support, eventually collapsing to form dissolution sinkholes at the surface.
A significant natural cause is the dissolution of evaporite minerals, such as gypsum and halite (rock salt), found predominantly in West Texas and the Panhandle. Gypsum and salt are much more soluble in water than limestone, meaning they can dissolve and create subsurface cavities much faster. When groundwater contacts these salt and gypsum beds, it leaches out the minerals, creating large, deep voids. The overlying rock layers then subside or collapse into the cavity, resulting in a collapse sink.
Man-Made Subsidence and Collapse
Many of the most dramatic ground collapses in Texas are directly or indirectly related to human resource extraction. Large-scale removal of subsurface fluids, such as groundwater, oil, or natural gas, destabilizes the rock structure above. This withdrawal reduces the buoyant support and pore pressure within the rock, leading to ground subsidence, which is a gradual sinking of the land surface.
In West Texas, extensive oil and gas activities, which have “punctured” the region since the 1940s, have been linked to significant ground movement. The injection of massive volumes of wastewater and carbon dioxide into the earth can alter subsurface stresses and fluid pressures. Conversely, the extraction of hydrocarbons and resulting depressurization can lead to massive areas of subsidence, with ground surfaces sinking by as much as 40 inches across 4,000-square-mile areas of the Permian Basin.
A specific type of human-induced collapse is associated with the dissolution of deep salt layers. The famous Wink Sinks, a pair of large, expanding sinkholes in West Texas, illustrate this phenomenon. These collapses likely occurred because older, improperly cased, and abandoned oil wells created a conduit for fresh water to travel downward. The water reached the highly soluble Salado salt formation, rapidly dissolving the salt and creating massive underground cavities that migrated upward until the surface failed. Solution mining, which intentionally pumps water into salt beds to create brine for commercial use, has also caused catastrophic collapses when the resulting underground voids failed.
Regions Where Sinkholes Are Prevalent
Sinkhole activity in Texas is concentrated in two major geographical zones, each defined by distinct geological conditions. The first zone encompasses Central Texas, including the Edwards Plateau, the Hill Country, and the Balcones Fault Zone. This region is dominated by Karst terrain, where the dissolution of Cretaceous limestone formations is widespread.
The concentration of sinkholes here is directly related to the underlying Edwards Aquifer, a vast network of highly permeable limestone channels. State geological surveys have mapped thousands of caves and sinkholes in this region, which act as direct entry points for surface water to recharge the aquifer. The geological concern in Central Texas is primarily the risk of sudden collapse and the potential for groundwater contamination.
The second major zone is located in West and Panhandle Texas, specifically within the Permian Basin. This area is prone to sinkholes caused by both natural evaporite dissolution and human-induced subsidence. The most concerning activity in the Permian Basin is the large-scale subsidence and formation of collapse sinks driven by decades of oil field activities. This combination of natural gypsum karst and man-made salt dissolution makes West Texas a high-risk area for ongoing and future collapse events.