The reworking process, also known as the rising and falling of sea levels allowed the concentration of these deposits in certain geographic areas like Florida. These deposits still serve a purpose for the United States today, for they account for a significant portion of the phosphate produced in the country. .
Although fossils of animals were seen before the Pliocene Epoch, this Era played the largest role for land animals in Florida. North America and South America were still connected allowing animals to migrate from continent to continent, this would be why similar fossils of animals are found in both North and South America. The Gulf of Mexico became isolated because ocean currents were interrupted. The Great American Interchange emerged from the exchange of flora and fauna from South America.2 Some of the most diverse faunas accumulated southwest Florida at this time because sea levels were fluctuating greatly. However, animals quickly became extinct due to the Ice Age and animals such as mammoths strolled across Florida. The glacial period led to low sea levels, so erosion and dissolution of limestone occurred. But as the ice age ended, sea levels rose leading Florida to shrink in size. This also created a change in the climate in which it became much wetter. The wetter habitat and thick layer of peat being deposited led to the formation of the Everglades. .
The erosion of limestone continued causing karst development. Karst is a type of topology underlain by soluble limestone. The karst landscape came to be largely due to the dissolving action of ground water made weak through acidic rain. After time this caused unusual surface-subsurface features that include sinkholes, vertical shafts, disappearing streams, springs and even complex underground drainage systems and caves. Skipping a bit ahead to our current era the Holocene Epoch, sea levels reached its current state and man began to take over the land.