From the time I was very young I remember visiting the fresh water springs found all around Central Florida. My entire family (aunts, uncles, grandparents, cousins, friends, etc.) would pile in cars early in the morning and drive to one of the local state parks for swimming and a big picnic.
For those of you who have never been to one, the springs around central Florida spill millions of gallons of crystal-clear, 72°F water straight up from the aquifer below. That means the water coming out of the giant hole in the ground was the cleanest, clearest water you will ever see.
It’s like swimming in a perfectly clear aquarium. Don a mask and you can see everything beneath the surface (gar, mullet, turtles, bream, bass and manatees) as if they’re all floating in mid-air against an azure blue background.
The hole itself is called the vent and looks like the earth just cracked open under water. Swimming over it always gave me a pit in my stomach. It feels less like swimming more like flying over a deep limestone canyon, looking down at the rocks and cliffs below. I was always waiting for that moment when gravity would catch on that I was somehow cheating and finally grab me, pulling me down onto the rocks below. But even with the fear the vent always called to me.
Just inside the rim of the tiny chasm was the greatest treasure I could find, more valuable than gold and even more coveted by my science geek heart than anything else in the natural world – shark teeth. As the water from the aquifer pushes its way through the limestone it carries with it fossils trapped in what was once ancient seabed. Sharks can shed over 30,000 teeth in their lifetime so it is one of the most abundant types of fossils to find in Florida, but even so they aren’t just lying around in the sand. You still have to know where to look.
Last week I took the kids to one of our favorite springs, Wekiwa Springs State Park. We’ve been many times in the past but it’s been many years since I’ve attempted to make the 20-foot deep dive to the vent opening looking for fossils. After a few attempts, I finally made it to the bottom and came up with a handful of limestone gravel chock full of fossils.
After picking through the flotsam I was able to score six sharks teeth including one from a Hemipristis serra, an extinct species of weasel shark from the Miocene period (23.03 to 5.33 million years ago.) Along with the shark teeth I also found a few sting ray teeth and some fossil invertebrates. All in all a great find.
Here are some helpful links:
Anatomy of a spring – http://www.sjrwmd.com/publications/pdfs/ps_springs.pdf
A “Quick & Dirty” Guide to Fossil and Recent Shark Teeth – http://www.elasmo-research.org/education/evolution/guide.htm
Information on shark teeth at Shark Savers.com – http://www.sharksavers.org/en/education/biology/shark-teeth1/
Florida State Parks – http://www.floridastateparks.org/