Sinkholes are depressions in the ground formed primarily by what process?

• A. Dissolution of limestone
• B. Volcanic explosions
• C. River erosion
• D. Tectonic movements

Answer: (A)

Sinkholes form when acidic groundwater dissolves soluble rocks like limestone, creating underground voids and caverns. Water that has absorbed carbon dioxide from the air or soil becomes carbonic acid, which dissolves the rock over time. When these underground cavities grow too large, the support for the overlying ground can fail and the surface collapses, producing a sinkhole. This process is typical in karst landscapes where limestone is common, which is why dissolution of limestone is the primary cause. Other processes—volcanic explosions, river erosion, and tectonic movements—can create depressions or other features, but they don’t produce the characteristic dissolution-driven voids and collapse seen in sinkholes.