Sinkholes are primarily caused by the collapse of the surface layer due to the loss of support from underground voids. These voids form when soluble rocks like limestone, chalk, salt beds, or gypsum dissolve over time through natural processes such as groundwater percolation and acidic rainwater erosion, which gradually remove the rock beneath the surface. This process is called dissolution. There are three main processes leading to sinkholes:
- Dissolution: Acidic water slowly dissolves carbonate rocks, creating underground cavities.
- Collapse: When the surface layer can no longer support its own weight due to void expansion below, it suddenly collapses.
- Erosion: Surface materials like soil can be washed away by water, further weakening the ground and causing it to cave in.
Sinkholes can develop naturally over many years but can also be triggered or accelerated by human activities like groundwater extraction, mining, leaking pipes, heavy rainfall, surface water drainage changes, soil disturbance, and construction. Changes in the water table, either through heavy rainfall or drought, also play a significant role in triggering sinkholes. The stability of the surface decreases as water moves or is removed, causing overlying material to collapse into the void below.
