Learn About Sinkholes

Sinkholes are one of the most predominant landforms in Florida. They are a naturally occurring, common geologic event that can pose great hazard to property. Many sinkholes develop naturally throughout Florida, yet in recent years sinkholes have seemed to develop with a much greater frequency - a much greater frequency that non-coincidentally occurs at the same time as Florida has experienced vastly greater development of land and ground water resources.

Sinkholes Like Drains

A sinkhole occurring in a field or in a farm grove is at best annoying or a nuisance. A sinkhole occurring in a neighborhood, under a street or highway, or around homes or buildings can be a disaster and cause substantial damage to property and structures.  Sinkholes can impact the environment, and they can often act like a natural "drain" and deplete rivers, streams and lakes by transferring the surface water directly into below ground aquifers - without the normal filtering that usually occurs to ground water before it enters the aquifer.

Ground Water Use

Much of Florida’s fresh water is obtained from these below ground aquifers - fresh water circulates into and out of storage in voids in and below the carbonate limestone underlying Florida. As greater population growth requires more and more water usage, ground water levels can drop to precipitously low levels, causing a sudden acceleration in sinkhole growth.

Karst

The limestone is slowly dissolved and weathered over millions of years, perhaps as quickly as a few millimeters annually. The dissolution and weather process which causes sinkholes is known as the geological term "karst." Karst topography includes springs, caves, disappearing streams, internally drained basins - and sinkholes!

Types Of Sinkholes

Sinkholes typically fall into four categories:

Dissolution Sinkholes - depressions in the limestone surface caused by the chemical erosion of limestone.

Cover-Subsidence sinkholes - formed over time as overhead materials slowly and gradually fill in surface voids and cavities.

Cover-Collapse Sinkholes - formed by movement of overlying cover soils into subsurface voids, but instead of happening slowly, a cover collapse sinkhole typically will occur very rapidly.

In fact, most lakes in Florida are actually sinkholes - they are subsidence depressions that have slowly formed over time, and water has formed in the depression bowl. Some storm water runoff lakes are in fact sinkhole drains - designed to quickly drain storm water into the aquifer.  

Sinkholes Seasonal

Since water has such a huge impact on sinkhole formation, it is understandable that sinkhole formation typically can follow the "wet" or "dry" seasons of Florida weather. Most sinkholes occur when groundwater levels are particularly low - such as during prolonged droughts or during the dry season from January through May. In fact, from 1948 through 1997, most new sinkholes formed in April and May - the end of the "dry" season, and also in January - when nightly freezes and frost can lead to excessive plant watering, thus depleting the ground water levels.