sinkholes

A sinkhole is a depression in the ground formed by the collapse of surface material into an underlying void, or by the dissolution of soluble rock near the surface by groundwater. They are common in karst landscapes where limestone, dolomite, gypsum, or salt rocks are present.

Most sinkholes develop as groundwater dissolves soluble rocks, enlarging cavities over time. In areas covered by sediment, voids underground can cause the overlying strata to sag (subsidence) or suddenly collapse if the cover becomes too thin or is forced away by drainage changes or water withdrawal.

Types include dissolution (solution) sinkholes, which form gradually as rock is dissolved; and collapse sinkholes, which occur when a cavern roof fails and the overlying material drops abruptly. There are also cover-subsidence sinkholes where surface settlement is slow and diffuse.

Sinkholes occur worldwide, particularly in regions with widespread soluble rocks, such as parts of the United States (notably Florida and Kentucky), Europe, China, and Turkey. They vary greatly in size, from a few meters to hundreds of meters in diameter, and can be shallow or deep.

Impacts and mitigation: They can damage roads, buildings, and utilities and affect water quality. Monitoring and risk management include hydrogeological surveys, drainage management, backfilling or grouting of voids, and land-use planning to avoid development over known hazard zones.