Geology - Florida Keys As land masses go, all of Florida is a mere child, having emerged from the sea as recently as 20 to 30 million years ago. For eons its bedrock base lay beneath the warm waters of the southern sea. Slowly it collected sediment, building limestone deposits that would eventually rise above the surface. As distant glaciers froze and melted, the seas rose and fell, forming and reforming the shores of Florida, depositing silt and bits of sea life.
The Florida Keys lie on a thick layer of limestone. The rock is covered by an ancient coral reef. In the lower islands, the porous Miami oolite, with its rich vegetation, appears once again. Low-lying islands with slight variations in elevation, the Keys boast a high point of 18 feet, on Windley Key. For the most part, however, they are very flat. There are over 800 islands large enough to appear on government charts, though many other tiny mangrove islets exist and are still aborning. About 30 of the Keys are enhabited.
To the east of the Florida Keys lies the only living coral reef in the continental United States. It is located between four and seven miles offshore, running parallel to the Keys from Key Largo to the Dry Tortugas. This living marine marvel, rising as high as a few feet below the surface of the water and descending to depths near the Gulf Stream, protects the Keys from the waves of the pounding Atlantic surf and hence from the development of sand beaches, a great surprise to many first-time visitors. |
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