Sinkholes

Although limestone dissolves very slowly in pure water, it is readily dissolved by carbonic acid, found in rainwater and decaying plant and organic materials.

As the Florida peninsula emerged from the ocean, it was populated by plants and animals and inundated with rain.

As rainwater passed through the soil, it picked up traces of carbonic acid and other various organic acids, which eroded and dissolved the limestone platform to create tunnels, caverns, ponds, streams, springs and sinkholes.

people standing in a sinkhole filled with water Sinkholes are a common occurrence in Florida; SWFWMD file photo.

Common to Karst

Sinkholes are a common feature in karst landscapes and are found throughout the Alafia River watershed. Where and when they occur depends on the thickness and chemical structure of the soil mantle (the “overburden”) as well as the circulation of the water stored in the limestone underground.

Slow and Fast

Sinkholes are most numerous in areas where the overburden is 30 to 200 feet thick. If it consists mostly of permeable sand, sinkholes tend to develop more slowly. If the overburden consists of impermeable clay, sinkholes can occur suddenly, without any warning.

Once a Lake

Some geologists believe that Tampa Bay was once a huge, shallow lake that began as a large sinkhole. Many thousands of years ago, as the earth warmed, the sea level rose until it breached the lake’s southwestern shore and Tampa Bay was formed.

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