What is a sinkhole?
Sinkholes are part of the slow, natural process of erosion in Florida’s limestone terrain that occur over thousands of years. These common geologic phenomena generally occur where the limestone is within a few hundred feet of the land’s surface.
Though most are only 10 to 12 feet in diameter, sinkholes have been known to expand to hundreds of feet in diameter. Many of central and north Florida’s lakes actually are the result of old sinkholes.
How do sinkholes form?
Rainfall percolating, or seeping, through the soil absorbs carbon dioxide and reacts with decaying vegetation, creating a slightly acidic water. That water moves through spaces and cracks underground, slowly dissolving limestone and creating a network of cavities and voids. As the limestone dissolves, pores and cracks are enlarged and carry even more acidic water. Sinkholes are formed when the land surface above collapses or sinks into the cavities or when surface material is carried downward into the voids.
Drought, along with resulting high groundwater withdrawals, can make conditions favorable for sinkholes to form. Also, heavy rains after droughts often cause enough pressure on the ground to create sinkholes.
Sinkholes can be triggered by human activities such as:
- Overwithdrawal of groundwater
- Diverting surface water from a large area and concentrating it in a single point
- Artificially creating ponds of surface water
- Drilling new water wells
In urban or suburban areas, sinkholes are hazardous because they can destroy highways and buildings. Sinkholes also can cause water quality problems. During a collapse, surface waters may leak into the aquifer, our underground source of drinking water.