ARROW Geology Water Karst - Apalachicola Region Resources on the Web

Land
Weather
Water
Types
Karst
Aquifers

Water: Karst
Windows into the truth

Millions of gallons a day of fresh water pouring out of holes in the ground, fresh water bubbling up into salt water, rivers that disappear only to pop up again a mile or more downstream - what kind of science fiction landscape is this?

It's karst, a kind of landform where the underground rock is easily dissolved by water. The word comes from a region in Slovenia called Kras that is famous for its caves.

Students get a sinking feeling on the Florida State University campus, 1962 (photo courtesy Florida Photographic Archives)

Not all the rock dissolves at the same speed, so the landscape get pockets here and there, some of which are big enough to form tunnels and caverns. If environmental conditions are right, these pockets fill with water. The pockets range in size from a pinhead to a concert hall. Some pockets are close to the ground surface, and if the weight of the soil on the pocket's roof becomes too great, the pocket collapses, forming a hole. These holes in the ground could become springs if there's enough water close to the surface that is under enough pressure. Otherwise, they become sinkholes - conduits into the underground water-storing rocks.

In the ARROW region are two karst areas, one in central and eastern Wakulla County and one in northern Jackson County. There's practically no barrier between the top of the land and the water-bearing rock below. The connection between the land surface and the aquifer is direct. It's why Chad Taylor of Jackson County calls karst features "windows into the truth."

Sources:

Fernald, E.A., and E.D. Purdum (eds.). 1998. Water resources atlas of Florida. Institute of Science and Public Affairs, Florida State University, Tallahassee.

Miller, J.A. 1999. Ground water atlas of the United States. U.S. Geological Survey.