This Earthcache is placed with the permission of Miami-Dade County’s Department of Parks, Recreation and Open Spaces, and The Environmentally Endangered Lands (EEL) Program. Miami-Dade County’s Endangered Lands Program’s focus is the purchase and conservation of environmentally endangered lands. The purchase and conservation of these lands ensure that they are shielded from development and will continue to thrive as natural habitats. For more information about the EEL Program, please use this link: Visit the EEL Program
SOLUTION HOLES
A solution hole is a geologic feature that is quite common in the Florida landscape. Much of Florida is karst terrain. Karst terrain is the generic term for landforms that have been shaped by chemical weathering due to the dissolution of the underlying carbonate rocks. In Florida, the carbonate may be limestone or dolomite. In this southern part of Florida, we have mostly limestone (Miami Limestone). Karst areas are characterized by solution holes, sinkholes, springs, caves, disappearing streams, and underground drainage channels. As rain falls through the atmosphere, carbon dioxide (from decomposition of organic material), nitric oxide (from lightning discharges), and sulphur dioxide (from burning fossil fuels) dissolve into the rainwater, forming an acidic solution, sometimes referred to as acid rain. In Florida, when this rainwater passes through decaying organic material in the soil, it becomes even more acidic creating the acid Carbonic Acid. Then, the acidic water contacts the limestone, which is made up of Calcium Carbonate, and a chemical reaction occurs that dissolves some of the carbonate rock, creating Calcium Bicarbonate which is always aqueous (liquid form).
This solution weathering process is called carbonation. Here are the formulae for the reactions:
CO2 + H2O → H2CO3
carbon dioxide + water → carbonic acid
and then...
H2CO3 + CaCO3 → Ca(HCO3)2
carbonic acid + calcium carbonate → calcium bicarbonate
This constant weathering and removal of small amounts of the limestone from cracks or voids, begins to create holes in the limestone base. This is a slow process, but over very long periods of time, solution holes form and continue to grow as the acidic rainwater collects and passes by gravity in the cracks and holes more frequently than the higher areas around the holes. With enough time, and depending on the nature of the limestone formation, a sinkhole, cave, or other larger feature may form.
HATTIE BAUER SOLUTION HOLE
This Park is at the highest natural elevation of the Atlantic Coastal Ridge (see GC42P2M), south of the Coconut Grove area. The southern terminus of the Ridge is in the area of Long Pine Key in the Everglades National Park. On the Ridge, you can find pine rocklands and tropical hardwood hammocks. This Park is a tropical hardwood hammock which generally contains visible small solution holes.
At the posted coordinates, you can see and study a very large solution hole. This solution hole is likely still growing, but measuring its growth would take many years. It is easy to see, as you walked into the park, how much organic material is available from the falling leaves and branches in this park. Additionally, you can observe numerous small solution holes in many areas of the park. You will also find a sign that discusses the largest solution hole. Please make all your observations from the area near the sign. Please do not cross the barrier that is in place around the solution hole.
We would appreciate if you could please report the following either in your log or via Email to eel@miamidade.gov. The number of cachers in your party. Any evidence of illegal dumping. Any evidence of human habitation in the preserve. Any evidence of damage to the shrubs or trees.
References: Florida Geological Survey. Florida Department of Environmental Protection. Washington University, Department of Chemistry, Acid Rain. National Parks Service. Wikipedia.
Optional photo: A photo of you or your party in the forest would be a nice addition to your log.
To get credit for completing this Earthcache, please send to our Profile Email, your best answers to the following questions:
1. What kind of water or rainwater can dissolve limestone rocks?
2. What compound is limestone made up of?
3. What is your estimated diameter (ft or m) across the opening of this solution hole?
4. What is your estimated depth (ft or m) from top to bottom of the solution hole?
5. From the sign at the posted coordinates, after the exotic invasive vines were removed, what kind of plant does this solution hole now support?
"When one tugs at a single thing in nature, he finds it attached to the rest of the world." - John Muir
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