The Blue Hole EarthCache
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This Earthcache is located on The National Key Deer Refuge, which was established in 1957 to protect and preserve Key deer and other wildlife resources in the Florida Keys. The refuge consists of approximately 9,200 acres of land that includes pine rockland forests, tropical hardwood hammocks, freshwater wetlands, salt marsh wetlands, and mangrove forests. These natural communities are critical habitat for hundreds of endemic and migratory species including 17 federally-listed species.
The Blue Hole
Approximately 100,000 years ago, the Florida Keys were a thriving coral reef! Most of Florida’s land mass was reduced to a thin strip of land called the Lake Wales Ridge. However,as time went on, the Earth’s climate shifted toward an ice age, glaciers began to form sucking up the ocean and our reef rose from beneath the waves! Eventually, plants and animals, including the white-tailed deer, colonized this new habitat.
The Florida Keys, as we know them today, were created around 10 thousand years ago when the earth gradually warmed from the preceding ice age. Sea levels rose from 350 feet below current levels, flooding much of Florida. Sea level rise created our chain of islands, isolating the plants and animals, including the white-tailed deer, from the mainland and the rest of their population. Species like the deer began to adapt to their island ecosystem until they eventually evolved into their own sub-species!
The geology of the Lower Florida Keys (Big Pine Key west to Key West) has been described in detail by Hoffmeister (1974). Marine carbonate sediments nearly 20,000 feet in depth underlie the Keys. Along this submerged platform, coral reefs developed in a band from present day Miami to the Dry Tortugas. Two limestone formations of marine origin are found in the Lower Florida Keys. Miami oolite, a medium-to hard limestone, overlies the Key Largo limestone formation. In the Lower Keys, Key Largo limestone is exposed only in a narrow band on the extreme southeast end of Big Pine Key. Elsewhere in the Lower Keys, it is overlain by Miami oolite, formed during the Pleistocene era in a high-energy, shallow water environment containing an abundance of calcium carbonate. The configuration of limestone strata in the Lower Keys allows for the development of the freshwater lenses found there.
"The Miami Limestone consists of two facies: an oolitic facies and a bryozoan facies. The oolitic facies consists of white to orangish gray, oolitic limestone with scattered concentrations of fossils. Ooliths are small rounded grains so named because they look like fish eggs. Ooliths are formed by the deposition of layers of calcite around tiny particles, such as sand grains or shell fragments. The bryozoan facies consists of white to orangish gray, sandy, fossiliferous limestone. Beds of quartz sand and limey sandstones may also be present. Fossils present include mollusks, bryozoans, and corals." (visit link)
The Blue Hole is an old limestone quarry. The rock was used to build many of the original roads on Big Pine Key in the 1930’s and 40’s. There is no inlet or outlet to the Blue Hole, its existence is dependent on rainfall and from saltwater which flows through the surrounding porous limestone. Because freshwater is lighter than saltwater, it floats on top, forming a lens. Freshwater is very important in this island ecosystem and the Blue Hole provides a vital resource to many animals, including the Key deer, American alligator, turtles, and many species of birds. The Blue Hole also is home to many different types of fish, in fact, there are both saltwater and freshwater species here!
Stop by the Refuge Visitor Center on your way to this Earthcache for a checkoff list of bird species, and other helpful information like how to identify poisonwood! The Visitor Center is located in the Big Pine Key Winn Dixie Shopping Plaza on Key Deer Blvd, just north of the light on US1. You can also call at (305) 872-0774
To receive credit for finding this Earthcache:
1) When was the National Key Deer Refuge established?
2) What is the purpose of the Refuge?
3) Approximately how large is the Refuge?
4) Name at least 3 of the habitats of the Refuge.
There once was a gator named Allig
Who lived in a place called Blue Hole.
Some people fed him while others they swam
But most of the water was his dinner bowl.
So Allig grew bigger with each passing week
And no longer called his visitors Sir.
He mistook a young miss for his usual fish
And one morning before breakfast Allig-ate-her.
Alligators are wild animals and should be treated as such. Swimming or feeding the alligators is prohibited for your own protection.
PLEASE BE ADVISED: ONLY REFUGE STAFF MAY PLACE CACHES ON REFUGE LANDS. ANY ILLEGAL CACHES WILL BE REMOVED.
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