Sinkhole is a bowl-shaped depression in Earth’s surface that forms where the ground sinks, collapses, or washes into underground openings. Sinkholes are also called sinks or dolines. As sinkholes develop, they can damage roads, buildings, and other structures that lie above them. Rarely, sinkholes that form suddenly can kill or injure people. They can also allow polluted water to drain rapidly, contaminating supplies of ground water (water beneath the surface) used for drinking. Large sinkholes may fill with water to become lakes or ponds.
The openings that can cause sinkholes form where mildly acidic ground water dissolves underground rock. These openings most often develop in a rock called limestone, but sinkholes also form in anhydrite, dolomite, gypsum, marble, and other easily dissolved rocks. Depressions that resemble sinkholes can develop where fast-flowing water quickly erodes the soil. However, geologists only consider a depression a sinkhole if it is caused by the dissolving of underground rock.
Sinkholes often form during droughts or when farmers drill many wells to get water for irrigation. The ground water becomes depleted, causing the rock and soil above to collapse. Intense rainstorms can also cause sinkholes by weakening the soil above an opening.
Rocks that can develop sinkholes lie beneath about 10 percent of Earth’s ice-free land. Sinkholes are more common in the Northern Hemisphere, where limestone is more widespread. In the United States, sinkholes develop most often in the East and Southeast, where they can cause extensive and costly damage.
