Together with a warm, wet, subtropical climate, the geology of South Florida provides well-suited conditions for the Everglades large marshland and ecosystem. The water-bearing rock and soil are due to the layers of porous and permeable limestone that affect the climate, weather and the hydrology of South Florida.
The geologic history explains the properties of the rock underneath the Everglades. At one point, the crust underneath Florida was part of the African region of the supercontinent Gondwana. North America merged with Africa about 300 million years ago. Sedimentary rock with igneous rock covered Florida due to volcanic activity centered on the eastern side.
About 180 million years ago, continental rifting began to separate North America from Gondwana. As part of Africa, Florida was initially above water. During the cooler Jurassic Period, the Florida Platform became a shallow marine environment and sedimentary rocks were deposited. Most of Florida remained a tropical sea floor during the Cretaceous Period. Since the bedrock was formed, the peninsula has been covered by seawater at least seven times.
Consistent flooding in the Everglades is fed by the flowing rivers in central Florida:
The Kissimmee River empties directly into Lake Okeechobee. The lake is vast but considered a shallow lake. It covers 730 square miles with an average depth of 9 feet. Where the land is consistently flooded throughout the year, soil deposits from the Everglades basis indicate deposits of peat. When the flooding is shorter, calcium deposit is left behind.
Where water rises and falls depending on the rainfall, deposits occur. This does not occur where water is being stored in the rock from one year to the next. When limestone is exposed, calcium deposits are more present.
At one point, from the tip of Florida to Orlando there was a single drainage unit. When Lake Okeechobee capacity was exceeded due to rainfall, in a southwestern direction, it emptied into the Florida Bay. The Everglades began at the southern edge of Lake Okeechobee and flowed for approximately 100 miles, emptying into the Gulf of Mexico prior to urban and agricultural development.
The Kissimmee river travels slowly at about a half a mile a day. The slow movement of the broad and shallow river is known as sheet flow. This is how the Everglades got its nickname River of Grass. With the water traveling so slow, it can take months and sometimes years for it to reach its final destination, the Florida Bay.