Florida’s natural geographical water movement systems are unique with many “methods” of movement. Many of the methods are easy for all to see. Such as rain, a river, lakes, bogs, and natural springs to mention a few. However, many methods occur every day, unknowingly all around us.
One method of water movement is evaporated water stored in the atmosphere as clouds and condenses, then falls as rain. Another water movement system is water discharged from the ground as natural springs, and it evaporates and condenses, forming new clouds. So a continuous cycle of evaporation and condensation is formed from atmospheric heating by day, causing water to rise as evaporation and fall to earth in the form of rain. All this rain water accumulates “re-charging” rivers and lakes above ground and below ground as well in the form of springs and aquifers. (2) This is called a “hydrologic cycle.” Meaning the water moves based on hydrological forces above and below ground. Each method in the “system” is critical in creating a naturally occurring, stable, and sustained water movement phenomenon. The topic of discussion here will be one method called “karst” rock based methods of water movement.
How Does Karst Rock Originate?
As sea level would rise and fall, covering then receding over the Florida peninsula occurring for millennia (thousands of years) and the Appalachian mountain range eroded, sand and clay were deposited on what became the Florida peninsula (1). This allowed a geological formation of confining materials that assist in accumulating water. Lower land areas that could hold water formed lakes, ponds, bogs, along with other forms of natural water confinement.
Karst is a naturally occurring limestone-based rock in southwest central Florida. It is southwest central Florida’s type of bedrock. Karst lies beneath the Tampa Bay, FL area and runs north along the Florida gulf coast to the Big Bend area in the northwest peninsula of Florida and inland about 40 to 50 miles.
How Does Rain Water Effect Karst Rock?
Rainwater, which is normally only slightly acidic, fills confined spaces and slowly dissolved the limestone substrate, creating holes, crevices (2), caves, and in some cases, sinkholes falling into vast underground caverns, and aquifers. Florida’s karst rock deposits are a direct result of the above described ancient geological formations. The cracks, caves, and channels are inner connected and form a “conduit” through which water can flow forming underground “rivers” or aquifer and spring systems.
Karst Landscape Characteristics
A karst landscape is very efficient at moving water from the surface down to the aquifers underground. (2) The characteristics of karst landscape form on permeable soluble formations such as limestone, which is the case here. Karst landscapes are naturally acidic and appear parched. The grass is sparse as is all but a few hardy floras such as palmetto plants and sand spurs. The sandy soil is dry, hot, and uninviting because of the karst landscape absorbs vast amounts of southwest central Florida’s tropical rains leaving little moister at the surface.
Regionally, karst at the surface lies near the Gulf of Mexico, from Tampa Bay, where karst rock is at or near the surface, then continues northward along the gulf. South of Tampa Bay, a thick layer of clay confines the karst rock. Increased confinement reduces re-charge of “aggressive” water slowing chemical dissolution, making the karst rocks less susceptible to dissolving (1). Subsidence activity is naturally less frequent, and karst features are sparse at land surface, meaning less naturally occurring “near surface” aquifers and springs.
Karst Aquifers Create Artesian Springs
Natural springs forming in karst rock are “artesian” in nature and frequently discharge large volumes of crystal clear water. One example of karst rock springs is located in Crystal River, FL. Enough fresh water is discharged from 3 primary springs (2 small and 1 large) daily forming a crystal clear river some 10 miles long and as much as a half mile wide. The river and tributaries continue flowing eventually into the Gulf of Mexico. This is one of Florida’s many freshwater scuba diving hot spots.
The most abundant concentrations of springs in the world are located in northern and central Florida. Wakulla Springs, just outside Tallahassee, claims the distinction of being the largest and deepest spring discovered on the planet.
Karst is shown to be the basis for many of southwest central Florida’s unique naturally occurring water movement system methods. It employs cracks, holes, caverns, aquifers to confine rain water. By doing so, karst rock perpetuates Florida’s hydrologic cycles, creating fresh, clean water on a daily basis.
Karst Topography. USGS,
Karst topography | Alafia River Watershed Excursion. Southwest Florida Water management District