What Causes Sinkholes?

Sinkholes are depressions that form when the underlying limestone bedrock is eroded or dissolved by groundwater. Water, especially when it is slightly acidic, can dissolve soluble rocks like limestone over time (see also acid rain). The wearing away of limestone in contact with the water creates underground cavities and voids. When the structural integrity of the surface above these areas is compromised, it can collapse, creating in a sinkhole. This natural process is relatively common in areas with karst topography, where the landscape is characterized by such soluble rocks.

Fluctuations in water levels can also lead to sinkhole formation. When groundwater levels drop, the physical reinforcement that the water provides to the underground cavity also falls, which increases the likelihood of the cavity’s ceiling giving way. Conversely, heavy rainfall or flooding can saturate the ground, adding weight and pressure above a cavity that can also trigger a collapse. Such changes in water levels can be natural occurrences or driven by or exacerbated by human activities, such as excessive removal of groundwater for irrigation. In addition, building construction, drilling, mining, and other activities that disturb the ground can weaken the structural integrity of the surface and make it more susceptible to collapse.