Disappearing River EarthCache
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If you have found other EarthCaches in Florida, you are probably well advanced in your knowledge of karst geology. Karst landforms are generally the result of mildly acidic water acting on soluble bedrock such as limestone. The carbonic acid that causes these features is formed as rain passes through the atmosphere picking up CO2, which dissolves in the water. Once the rain reaches the ground, it may pass through soil that may provide further CO2 to form a weak carbonic acid solution: H2O + CO2 ? H2CO3 (the acid). Recent studies of sulfates, in karst waters, suggests sulfuric acid and hydrosulfuric acid may also play an important role in karst formation.
This mildly acidic water begins to dissolve the surface along with any fractures or bedding planes in the limestone bedrock. Over time, these fractures enlarge as the bedrock continues to dissolve. Openings in the rock increase in size, and an underground drainage system begins to develop, allowing more water to pass through the area, and accelerating the formation of underground karst features. This geological process, which will take thousands of years, is characterized by unique features such as sinkholes, fissures, caves, disappearing streams & rivers, springs, rolling topography, and underground drainage systems.
The Santa Fe River is a big, dark brown river that drains a 1,380 square mile area.
In O’Leno State Park in High Springs, FL, the Santa Fe River suddenly disappears underground into a sinkhole (a karst formation) and does not reappear until 3 miles downstream in River Rise State Park.
To see this phenomenon yourself drive to the park, pay the small admission fee and proceed to the day use area. Park and walk to the suspension bridge over the river. Here you have a choice; you can cross the bridge and walk the entire River Loop trail (1.4 miles) or without crossing the river, turn right and follow the River loop for .5 miles of easy walking to the sink.
To secure your new found knowledge, make these observations along the way. Please e-mail your answers to us (not in the log!) and post a picture of yourself and your GPS at the sink.
1. Observe and estimate the rate of flow of the river at the suspension bridge. You can answer in feet per minute watching a small branch or leaf in the river and estimating the distance it covers in a minute. Conversely, you can use slow, medium, fast or very fast. How does this compare to the river flow as it approaches the sink?
2. Can you tell exactly where the water falls into the sinkhole?
3. The area just beyond the sink is called a ______________ ____________. How did the early settlers and later the federal government utilize this geological feature?
4. A sign at the GZ mentions concern about two living creatures. What are they?
5. Ranger Andrew who gave us permission to place this Earth Cache poses this question. Scientists who have studied the sink and rise of the Santa Fe river say that the volume of water that exits at the rise exceeds that that sinks where you are standing. (Hint look at the sign near the sink). Can you explain why?
O’Leno has an interesting history of the Civilian Conservation Corps, was the site of a once vibrant small town and offers recreational opportunities for the whole family. To visit River Rise State Park, revisit the ranger station for directions and a combination for the gate.
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