Sinkholes are holes or depressions in the ground caused by the collapse of the surface layers into holes or caverns hidden beneath the surface of the Earth. They can occur suddenly or develop over the course of time and may be either of natural or artificial origin. Their size varies from 1m in depth and diameter to as much as 600m.
Safeopedia Explains Sinkholes
Natural sinkholes are most often formed when limestone rock beneath the ground’s surface is dissolved and eroded by water creating a cavity below the surface. If the upper layers collapse into the cavity, a sinkhole is formed. However, sinkholes also occur as a result of mining activities, burst water-mains and excessive pumping out of ground water that leaves underground caverns empty. Sinkholes can range in their effects from a minor inconvenience to a major calamity that can swallow up buildings. Florida is particularly prone to natural sinkholes, and many of the lakes in Florida are remnants of old sinkholes.