Sinkholes are caused primarily by the collapse of the surface layer due to loss of support from underlying voids or cavities formed by the dissolution or erosion of soluble rock beneath the ground. They commonly occur where bedrock is limestone, carbonate, salt beds, gypsum, or other soluble rock. Groundwater percolation dissolves this rock over time, creating underground voids. When the surface material above these voids can no longer support its own weight, it collapses, forming a sinkhole. Three main processes cause sinkholes:
- Dissolution: Acidic rainwater or groundwater dissolves the soluble rock, gradually creating underground cavities.
- Collapse: When the supported ground above a cavity collapses suddenly, often triggered by heavy rainfall or added surface weight.
- Erosion: Water washing away soil and sediment weakens the ground, contributing to a collapse.
Additional factors can trigger or accelerate sinkhole formation such as changes in water tables, heavy rain, drought, human activities like groundwater extraction, mining, leaking pipes, construction, and altering surface drainage. These factors destabilize the underground voids or saturate surface soils, leading to collapse. In summary, sinkholes form when the ground beneath the surface dissolves or erodes away, removing support and causing the surface to suddenly or gradually cave in.
