Welcome to an EarthCache!
Unlike traditional geocaches, there is no container to find and no logbook to sign. Instead, EarthCaches bring you to a location where you can learn about the unique geology of our planet. At this site, you’ll explore a monument built from fossil reef limestone and discover how its porous structure connects directly to Florida’s underground aquifer system. To claim credit, you’ll make observations and answer questions about what you see.
Logging Tasks
To log this EarthCache, visit the coordinates and make observations about the example of fossil reef limestone:
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Porosity Observation: Describe the holes and cavities you see in the rock. Are they small and uniform, or large and irregular? Do they look like coral patterns, or weathered voids?
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Water Connection: Based on what you see, explain how water could move through this rock. Would it travel quickly, slowly, evenly, or in unpredictable paths?
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Weathering Evidence: Look closely—are some of the pores smooth and rounded, while others look sharp or jagged? What does this suggest about the way weathering (rain, salt spray, or wind) has shaped the rock since it was quarried or exposed?
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Size Comparison: Compare two blocks of stone. Which one seems more porous, and how might that affect its ability to store or transmit water?
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Photo: Post a picture of yourself (or your GPS) with the fossil reef sample behind you.
Earth Science Lesson
When you look at this locaqtion, you’re not just seeing rock—you’re looking into Florida’s ancient water system. This stone is Key Largo Limestone, a fossilized coral reef that formed about 100,000 years ago when sea levels were higher and the Keys were under shallow, warm seas. Over time, coral skeletons and marine debris compacted and hardened into limestone.
What makes this rock unique is its porosity: all the holes, tunnels, and cavities you see are not random. They are the preserved framework of ancient corals and the spaces between them. These openings make the limestone act like a sponge, capable of holding and transmitting water.
In Florida, this porous limestone is directly tied to the aquifer system—the underground reservoir that supplies drinking water to millions of people. Water soaks into the limestone, flows through it, and emerges in springs and wells. But this same porosity also makes the aquifer vulnerable: pollutants and saltwater intrusion can travel through the rock just as easily as clean water.
By observing this fossil reef rock, you can see firsthand why Florida’s water supply is related to the geology and is both abundant and fragile.
Why This Spot?
Most Floridians benefit daily from water that flows through this very type of rock, yet few realize they can see the aquifer’s structure in plain sight. This wall gives a unique, dry-land window into Florida’s water story—where ancient coral reefs became both the rock beneath our feet and the water reservoir that sustains life today.
References
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U.S. Geological Survey (USGS) – Florida’s Geology and Groundwater.
https://www.usgs.gov
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Florida Geological Survey (FGS) – Geology of Florida.
https://floridadep.gov/fgs
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South Florida Water Management District (SFWMD) – Water Resources and the Biscayne Aquifer.
https://www.sfwmd.gov
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University of Florida, IFAS Extension – Florida’s Aquifers.
https://edis.ifas.ufl.edu
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National Park Service (NPS) – Geology of Biscayne and Everglades National Parks.
https://www.nps.gov
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Randazzo, A.F. & Jones, D.S. (1997). The Geology of Florida. University Press of Florida.
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Fish, J.E., & Stewart, M.T. (1991). Hydrogeology of the Surficial Aquifer System, Dade County, Florida. USGS Water Resources Investigations Report 90–4108.
Credits: The Earth science information for this cache was compiled from U.S. Geological Survey, Florida Geological Survey, University of Florida, and other reputable sources to provide an accurate and educational learning experience.
AI Disclaimer: Parts of the text on this EarthCache page were edited with the assistance of AI tools (ChatGPT). AI was used to check scientific sources, ensure against plagiarism, and help craft a lesson that is unique and not duplicative of nearby EarthCaches. The cache owner created, verified, and is fully responsible for all content presented here.