The sudden and sometimes catastrophic subsidence associated with localized collapse of subsurface cavities (sinkholes) (fig. 8) is detailed in two case studies. This type of subsidence is commonly triggered by ground-water-level declines caused by pumping and by enhanced percolation of ground water. Collapse features tend to be associated with specific rock types, such as evaporites (salt, gypsum, and anhydrite) and carbonates (limestone and dolomite) (fig. 9). These rocks are susceptible to dissolution in water and the formation of cavities Salt and gypsum are much more soluble than limestone, the rock type most often associated with catastrophic sinkhole formation.

Evaporite rocks underlie about 35 to 40 percent of the United States, though in many areas they are buried at great depths (Martinez and others, 1998). Natural solution-related subsidence has occured in each of the major salt basins in the United States (Ege, 1984). The high solubilities of salt and gypsum permit cavities to form in days to years, whereas cavity formation in carbonate bedrock is a very slow process that generally occurs over centuries to millennia. Human activities can expedite cavity formation in these susceptible materials and trigger their collapse, as well as the collapse of pre-existing subsurface cavities. Though the collapse features tend to be highly localized, their impacts can extend beyond the collapse zone via the potential introduction of contaminants to the ground-water system. Two cavity-collapse case studies — Retsof, New York, and west-central Florida — document human-induced cavity collapses in salt and limestone, respectively.

SOURCE: USGS Land Subsidence in the United States

Florida has more sinkholes than any other state...

Sinkholes: What is a sinkhole?

Sinkholes are depressions or holes in the land surface that occur throughout west central Florida. They can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone.

Hydrologic conditions, including lack of rainfall, lowered water levels, or, conversely, excessive rainfall in a short period of time, can all contribute to sinkhole development. More facts about sinkholes can be found in the District’s Sinkhole Brochure.

View the Department of Environmental Protection's sinkhole database

Sinkholes are a common naturally occurring geologic phenomenon and one of the predominant land forms in Florida.

Many of the lakes in Florida are relic sinkholes. Sinkholes can be classified as geologic hazards sometimes causing extensive damage to structures and roads resulting in costly repairs. Sinkholes can also threaten water supplies by draining unfiltered water from streams, lakes and wetlands directly into the aquifer (underground water supply).
What if a sinkhole opens on my property?

• If your home is threatened, contact your homeowners insurance company.
• If extensive damage occurs to your house or property, notify the Office of Emergency Management for the county.
• If desired, the resident may make contact with a private contractor to evaluate the hole to officially determine if it is a sinkhole.

More information about sinkholes:
Florida Sinkhole Research Institute

Contact the Institute at UCF’s Civil and Environmental Engineering Department
P.O. Box 162450, Orlando, FL 32816-2450
phone: (407) 823-2280

Winter Park, Florida, 1981

A picture of the side of a sinkhole showing its strata

A picture of a cave showing stalagtites and stalagmites When groundwater discharges from an underground drainage system, it is a spring, such as Wakulla Springs, Silver Springs, or Rainbow Springs. Sinkholes can occur in the beds of streams, sometimes taking all of the stream's flow, creating a disappearing stream. Dry caves are parts of karst drainage systems that are above the water table, such as Marianna Caverns.

A picture of a cave showing stalagtites and stalagmites

Suggested reading: Lane, Ed, 1986, Karst in Florida: Florida Geological Survey Special Publication 29, 100 p. 

SOURCE:  Florida Department of Environmental Protection's sinkhole database

Blue Grotto is actually a sinkhole with good visibilty.  Depths reach 100 ft. Upon entering the sink you will encounter a very large cavern with writing on the walls. At a depth of 30 feet there is a fresh air bell so you can take off your mask and breath some fresh air. Continuing down, there is a large shaft that slopes down at a 90 degree angle.  At around 90 feet you will encounter silt that can be easily stired up. There are lights at 30 ft to illuminate the cavern. The owner, is very friendly and also manufactures dive, wreck and video lights...

Source: http://underwaterflorida.homestead.com/grotto.html

For More on the Underwater Sinkholes, Caves and Springs See Here
For More on Florida Caverns See Here

The bare minimum that a property owner needs to know about sinkholes or any other sudden subsidence of soils at a property is that these conditions might be very dangerous. Someone falling into a sink hole or into a collapsing septic tank could be seriously injured or even die. If a suspicious hole, subsidence, or depression appears at a property the owner should rope off and prevent access to the area to prevent anyone from falling into the opening, and then should seek prompt assistance from a qualified expert, geotechnical engineer, septic contractor, excavator, or the like.

Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice - Huge Data Base on Sinkholes around the USA

Sinkhole Information Site