Windley Key State Park has great historical, cultural, geological, and biological significance to the area. It is the site of a 20th century quarry for Key Largo limestone, which was used to build the Overseas Railroad. Completed in 1912, the Overseas Railroad was the first terrestrial connection between the mainland of Florida and Key West. After being largely destroyed by the Labor Day Hurricane of 1935, the rail line was abandoned and the remaining infrastructure was sold to the State of Florida. Utilizing surviving supports, the state converted them to the highway known as U.S. 1 in 1938. This highway was utilized until the early 1980s, when a new highway was constructed beside it. The most impressive part of the construction is a bridge that extends all the way from Marathon to Little Duck Key, a seven mile stretch! The original stretch of the aptly named “Seven Mile Bridge” is accessible by foot and is worth a visit.
Even after the railroad was completed in 1912, quarrying continued for the highly decorative Key Largo limestone that can be found in some of the older architecture of the area. Though the quarry is now defunct, examples of quarry equipment remain on the land today for visitors to view.
From a geological and biological standpoint, the Windley Key site offers exciting clues to the natural history of the region. The highest elevation in the entire Keys (16 feet) occurs within the Park, the remains of an ancient reef that flourished here tens of thousands of years ago.
Though initial sedimentation began millions of years ago, the uppermost limestone formations found here are the result of an ancient reef that reached its peak around 100,000 years ago, when sea levels were 25 feet higher than they currently are. At that time, this ancient reef was under 10 or more feet of water. A modern reef flourished at this time and it teemed with life.
Later, at the height of glaciation (26,000 ybp), sea levels dropped 350 feet below current levels and these reefs were exposed as land…the predecessors of the current island chain. As water receded, the life on the former reefs were compacted and fossilized into what is called Key Largo Limestone. It contains a countless number of marine organisms, cemented together with calcareous sediment and is prized for its aesthetic appeal. This Key Largo limestone differs from Miami Limestone (which is found in Miami and the Lower Keys) in this respect. Miami limestone is composed mainly of smaller sediments, while Key Largo limestone has numerous inclusions of large marine fossils…a result of being a massive ancient reef.
As the last glacial period came to a close, melting glaciers began to refill the oceans. By about 6,000 years ago sea level had risen to about its current level, leaving the chain of small islands now known as the Florida Keys. During the sea level rise, as water spilled over the continental shelf, it cut passes between the limestone structures, creating the individual islands of the Keys. The larger masses in the Upper Keys were able to withstand a lot more flow without channeling and now are able to shield shallow, eastward reefs from the influx of water from the Florida Bay. Ancient, highly fossilized limestone is preserved near the surface in these areas. The Lower Keys were more diminutive, so more channeling occurred. They do not offer such protection to the eastern/southern side, so developed shallow reefs are sparse there. Miami limestone dominates the upper layers of rock in the south because large amounts of precipitated calcareous sediment have accumulated on top of the lower-lying Key Largo limestone as a result of the influx of warmer, more saline and nutrient rich waters from the Florida Bay.
Looking at a map of the Florida Keys, it is possible to see the difference between these areas visually. The Upper Keys (north of Big Pine Key) are much longer on an east-west axis than their Lower Keys counterparts. The Lower Keys have a longer north-south dimension to them, riddled with numerous passes from the Florida Bay to the Atlantic Ocean.
A thin layer of rich soil developed on the islands, allowing for vegetative growth. The culmination of the events that created Windley Key provide for a very diverse assemblage of trees on the Island. The park offers five different hiking trails to explore the habitat, highlighting over 40 species of native trees and plants in the tropical hardwood hammock forest. Visitors are likely to see many birds, insects and small reptiles, but mammals are sparse in this island forest community.
At the end of the trails, an education center helps to fill in where the trail guidebook leaves off. Displays help to demonstrate the formation of coral reefs and island forest communities. Information is presented on a level that appeals both to serious scientists and curious children.
Windley Key State Park is a must see for visitors in my opinion. If you enjoy birds, reptiles, trees, plants, hiking or history…you won’t be disappointed.
Read dive logs from each day of the trip!
Dive Log – Saving Coral Reefs: