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The
Geology of South Florida
South Florida is one of the youngest areas, geologically, in the continental United States. The sub-tropical climate and the long hours of sunshine throughout the year make this an ideal place for growing tropical plants. Temperatures rarely go below 32 degrees F. in the winter and usually this is only for a few hours. Total yearly rainfall can approach that of tropical climes with 10 inches in 24 hours possible. The cities of south Florida were built along the Atlantic Coastal Ridge. This is the highest naturally formed land in south Florida and runs along the east coast. The original settlers built on it because this area was not prone to flooding. At a height up to 14 feet above the water table only hurricanes or an unusually heavy rainy season would cause flood conditions. The Atlantic Coastal Ridge is mostly a rock formation made up of oolitic limestone. This limestone has been used extensively in architecture here and is typical of "old Florida" structures. Often this rock is referred to as coral rock, but usually it is oolitic limestone. Oolites form when microscopic particles that are floating in the ocean are coated with calcium carbonate and eventually fall to the floor. The particles are egg shaped and hence the name oolite. The rock was formed through the process of sedimentation when south Florida was under water several times during the last few ice ages.
Coral rock also occurs in this area but it can be distinguished from oolite by the coral fossils found in the rock (oolite has few fossils). Key Largo, the northern most island in the Florida Keys, is where coral rock has been extensively mined and is where the name "Key Stone" comes from. West of the Atlantic Coastal Ridge is the Everglades. This swampy "Sea of Grass" is only a foot or two above sea level and contains extensive limestone formations. The rock in the Everglades is also characterized by fossils, but in this instance over 95% of those fossils are of a single species of Bryozoa (a small aquatic animal that forms moss-like colonies). The native flora of south Florida is a mixture of temperate plants at the southern most point of their range and tropical plants at their northern most limit. There are few endemic plants found here because this area is too young geologically for new species of plants to have evolved. The species of animals and insects found here also come from both climatic zones. The natural history of this remarkable area is fascinating and over the next few months articles relating to this subject will be added to this section.
Contact:
Jeff Shimonski
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