Savannah of the Alachua EarthCache
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Visiting Paynes Prairie State Park and the town of Micanopy could make a great break from traveling I75 or a family friendly day long expedition. Both host an abundance of caches to delight every member of the family.
The Mystery
As a kid, I spent the summers here in Micanopy with my grandparents. When you visit this area, you can’t help but notice that there is more water than land, with many shallow lakes dotting the landscape. Also, there are lots of sinkholes. One of my grandfather’s favorite stories was about the tragedy that befell local farmers in 1891.
To start the story, forget Twitter, the internet and even phones. Your news came from someone who talked to somebody who had talked to somebody who had been into town (Gainesville). As far back as anyone could remember, Paynes Prairie had been a big grassy depression in the otherwise semi-tropical tangle of forest and hard won farm lands.
For the last generation, many families like yours made their living growing citrus, vegetables and melons. This would have been unheard of not too long ago when the long horse drawn cart journey over inhospitable roads made it impossible to get fresh produce to market. However, since the big rains of the 1870s Alachua Lake was a big. In fact it was so big that a steamship line developed to carry the produce across the lake to the Florida Railroad depot and from there to the markets hungry for oranges, grapefruit and out of season produce across the United States.
It is September of 1891 and the summer crops are in. It has been a drought year and no one is too alarmed that the lake level has dropped. However, one morning the lake is really down. Lots of lake bed showing. Fish flopping around. Over the next week this huge lake entirely disappears stranding boats, leaving alligators, fish and other wildlife high and dry and farmers with no means to get fruit to market.
So, what happened here? It might help to know that the other name of Alachua Lake is the Alachua Sink.
SINKHOLES and the AQUIFER
Sinkholes originate beneath the surface when groundwater moves through the limestone and erodes large voids, or cavities, in the bedrock. When water fills a cavity, it supports the walls and ceiling, but if the water-table drops, the limestone cavity is exposed to further erosional processes that eventually result in the collapse of the cavity, causing a surface indenture, or sinkhole. The sinkhole becomes a primary site of recharge, where surface water can enter the aquifer and replenish the groundwater supply.
On the surface, sinkholes may develop progressively as subtle, bowl-shaped depressions, or they may collapse suddenly into steeply sided, water-filled craters. The shape of the sinkhole, and the speed that it forms, depend on the size of the subsurface cavity and the thickness of the overburden (sediments or organic matter that rest on the limestone bedrock).
Alachua Sink is a SOLUTION SINKHOLE. For this kind of sinkhole, the overburden is thin or absent and the surface of the limestone bedrock is broken down by erosion from wind and surface water. A bowl-shaped depression, or solution sinkhole, naturally forms slowly and continuously as chemical and physical processes erode the rock. Many lakes in Florida are formed in this fashion.
The story is that the Alachua sink became clogged in 1871 with logs and other debris, retarding the escape of water. In 1891, drought and other conditions caused the sink to “unplug” and the water accumulated over many years drained back into the aquifer. Talk about “business interruptions”. How long do you suppose it took word to get back to New York that one source of fresh Florida produce had disappeared in such a dramatic fashion?
This happened more recently in 1999 when Lake Jackson in Tallahassee suddenly lost all its water into the aquifer. See (visit link) for pictures and more information.
Today
While there are many excellent examples of limestone erosion (Karst topography) throughout the Southeast, Paynes Prairie is unusual because of the size of the bowl. One theory for the size of the expanse you are viewing today is that it was formed by sucessive sinkholes ringing the edge of the Prarie that slowly, over time crumbled and expanded the original crater. If you hike one of the trails, you will pass innumerable sinkholes of all sizes.
The cords bring you to the Visitors Center at Paynes Prairie State Park.The second floor observation deck behind the visitor center is open whenever the park is open to visitors. Climb up one flight and look out to the prairie. Take a picture of yourself and your GPS with the prairie in the background and post in your log.
To show that you learned something about solution sinkholes, answer these questions and e-mail the answers to us. Do not post them in your log.
1. Using the compass on your GPS, what direction are your facing when you look out over the Prairie?
2. Estimate the distance across the soulution sinkhole from this view point. (Hint - look to the opposite tree line)
3. Can you see water across the bottom of the depression? If not, provide a reason why not.
4. If the sink again became clogged and a hurricane or two provided flood conditions, would the lake that was formed be deep or shallow?
5. If you want to climb the higher observation tower closest to the visitors center, is it to your right or left as you stand on the balcony and look out to the Prairie?
Paynes Prairie has nine well maintained trails, the La Chua Trail offering the best view the Alachua Sink and a year round supply of gator and migratory Sandhill Crane sightings.If you plan to hike, come prepared with water, sunscreen, bug repellant, hats, camera and hiking attire.
For a more tame experience, immerse yourself in the Florida of the 1930’s at the Marjorie Kinnan Rawlings Historic State Park in nearby Cross Creek or wander downtown Micanopy where it still feels like the 1950s.
FTF congratulations to AMTG who added to the lore of the Aluchua Sink!
Additional Hints
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