Sinkholes are caused primarily by the collapse of the surface layer due to a loss of support from below. This loss of support typically happens when underground rock, particularly soluble rocks like limestone, chalk, dolomite, salt beds, or gypsum, is dissolved by naturally acidic rainwater or groundwater. The water seeps into cracks and fissures, dissolving the rock and creating underground voids or cavities over time. When these voids become large enough, the ground above can no longer support itself, leading to a sudden collapse and formation of a sinkhole. Several processes contribute to sinkhole formation:
- Dissolution: Acidic water dissolves the rock below the surface, creating cavities.
- Collapse: The surface layer collapses when the cavity becomes too large to support the weight above.
- Erosion: Water erodes soil and sediments above these voids, weakening the ground.
- Human activities: Changes in groundwater levels due to pumping, mining, leaking pipes, heavy construction, and surface drainage changes can accelerate or trigger sinkholes by destabilizing the ground.
Triggers like heavy rain, drought followed by intense rain, or human disturbance can saturate, weaken, or remove soil and rock support, causing the surface to cave in. Sinkholes can form over many years but sometimes collapse rapidly when conditions change. In summary, sinkholes form due to a combination of natural erosion and dissolution of underlying soluble rocks and human factors that affect the stability of the ground above underground voids.
