The Everglades stands as a vast wetland ecosystem in South Florida, recognized globally for its distinctive character. Often described as a “river of grass,” this unique environment features expansive shallow waters flowing slowly across a broad landscape. Its ecological significance derives from this continuous water movement, which supports an array of plant and animal life. The formation of the Everglades is a story deeply intertwined with ancient geological processes, the movement of water, and the influence of biological activity.
Underlying Geological History
The foundation of the Florida peninsula, including the Everglades, began forming millions of years ago when the area was submerged under a warm, shallow sea. Over eons, marine organisms’ calcium carbonate remains accumulated on the seafloor. This deposition created thick layers of limestone bedrock, which today lies beneath the entire state. This porous limestone led to the development of karst topography, with features like underground caves and channels formed by the dissolution of rock by slightly acidic rainwater. This geological base dictates how water interacts with the land, influencing its storage and movement across the region.
The Water’s Journey
The defining characteristic of the Everglades is its unique hydrological system, which initiates far north of the wetland itself. Water originates in the Kissimmee River basin, north of Orlando, flowing southward through a chain of lakes, eventually reaching Lake Okeechobee. From Lake Okeechobee, a broad, shallow sheet of fresh water historically spilled over its southern banks. This “sheet flow” moved slowly across the nearly flat landscape, often less than a meter deep and sometimes up to 60 miles wide, extending towards Florida Bay at the peninsula’s tip. This continuous, slow-moving water created the conditions needed for the Everglades ecosystem to develop and thrive.
Shaping the Landscape with Life
The Everglades’ distinctive geological and hydrological conditions fostered specialized plant communities that further shaped the landscape, with sawgrass prairies (composed of a sedge, Cladium jamaicense) adapting to the slow-moving water and becoming a dominant feature. The decomposition of this dense vegetation, particularly in waterlogged, anaerobic conditions, led to the accumulation of peat and muck soils over thousands of years. This biological process contributed to the formation of elevated landforms known as tree islands or hammocks, which are slightly higher patches of ground supporting woody vegetation. The continuous sheet flow also carved out deeper, linear channels called sloughs, which are low-lying areas that channel water and generally remain wet year-round. These interactions between water flow, geology, and vegetation created the complex mosaic of ridges, sloughs, and tree islands that define the Everglades environment.