Sinkholes
are a common feature of Florida's landscape. They are only
one of many kinds of karst landforms, which include caves,
disappearing streams, springs, and underground drainage
systems, all of which occur in Florida. Karst is a generic
term which refers to the characteristic terrain produced by
erosional processes associated with the chemical weathering
and dissolution of limestone or dolomite, the two most
common carbonate rocks in Florida. Dissolution of carbonate
rocks begins when they are exposed to acidic water. Most
rainwater is slightly acidic and usually becomes more acidic
as it moves through decaying plant debris.
Limestones
in Florida are porous, allowing the acidic water to
percolate through their strata, dissolving some limestone
and carrying it away in solution. Over eons of time, this
persistent erosional process has created extensive
underground voids and drainage systems in much of the
carbonate rocks throughout the state. Collapse of overlying
sediments into the underground cavities produces sinkholes.
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.
Other subterranean events can cause holes, depressions or
subsidence of the land surface that may mimic sinkhole
activity. These include subsurface expansive clay or
organic layers which compress as water is removed,
collapsed or broken sewer and drain pipes or broken septic
tanks, improperly compacted soil after excavation work, and
even buried trash, logs and other debris. Often a
depression is not verified by a licensed professional
geologist or engineer to be a true sinkhole, and the cause
of subsidence is not known. Such events are called
subsidence incidents.
Suggested Reading
For sinkhole questions call 850-617-0301
Sinkhole Resources