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