Eighteen Sierra Club members and friends gathered at 9:00am on 5-May-2012 for a hike in the City of Gainesville’s Split Rock Conservation Area. Access to the park is located just west of I-75 along the south side of SW 20th Ave. Trip leaders, Karie Garren and Rob Hopkins, had the foresight to get a key to the small unimproved parking spot so we did not have to park along the road.
The ultimate destination of what turned out to be a leisurely three hour stroll was Hogtown Sink. This hydrologically active sinkhole, or swallet, is where the flow of Hogtown Creek, which drains eastern Gainesville, is channeled underground into the Floridan Aquifer. However, at the time of our visit, the drought had taken its toll and the creek was not flowing. Interestingly, farther upstream, Hogtown Creek and its larger tributaries were still flowing a couple of cubic feet per second (cfs) (The long term average flow measured at the SW 20th Avenue bridge is 11cfs). Apparently the stream’s feeble flow was entirely lost to evapotranspiration after it spreads out in the large hardwood swamps below University Avenue.
The water level in the sink was at record low level and large chert boulders that are normally underwater could be seen perched along the rocky rim of the sink. The sink is 145 feet deep below the water surface and has overhanging limestone walls. At the bottom, water disappears into a series of narrow vertical fissures. Where does the water go from there? No one knows for sure, but most investigators would have probably guessed it would head north to springs along the Sante Fe River. Now, however, with expanding population and groundwater pumping, there is a good chance it flows toward the cone of depression located beneath Gainesville’s Murphy well field. Certainly, water moving under Florida’s karst plains increasingly has to run a gauntlet of wells as it moves toward distant discharge points.
Tom Points Out the Split in Split Rock Hikers Checking out Split Rock
Along the way we stopped at Split Rock, a limestone bluff at the edge of Hogtown Prairie, a large wetland flanking Hogtown Creek below I-75. Split Rock is named for a narrow crack, just wide enough to walk through, in a large limestone outcrop. The cool and moist conditions in the crack are perfect for the primitive liverworts which cover the rock walls. The bluff also has several small caves as well as nice examples of solution chimney remnants. The group pondered the remains of a concrete retaining wall at the foot of the bluff which probably enclosed a shallow swimming pool when groundwater levels were higher. Split Rock has not been heavily publicized and is in great shape. It is not run-down by overuse or marred by graffiti.
We had five biologists along on the hike. We could hardly walk fifty feet before one of them would find something interesting to discuss. They seemed to know the names of every plant and animal we saw, or were damn good at making them up, and how they fit into the larger ecological scheme.
Karie Discusses Mushroom Nancy six feet underwater
Down in the bottom land we hiked through a beautiful forest of water elm, also known as planer tree. These are a true wetland species, as suggested by their Latin name – Planera aquatica. The biologists pointed out that the colonization of the more elevated parts of the bottom land by approximately ten year old loblolly pines showed that the area had not flooded for about a decade. This pretty much falls in line with the dry conditions we have experienced since the year 2000. Near the creek we found a fine stand of poison hemlock. Tired of your spouse?
There were still healthy red bay trees in the upland forest, but, ominously, several trees were seen that had recently succumbed to laurel wilt disease. This disease was first seen near Savannah Georgia in 2002, where an exotic ambrosia beetle was brought into port from Southeast Asia in packing crate wood. The beetles burrow into trees in the laurel family (Lauraceae) and kill them by releasing a fungus that clogs water-conducting tissue. Other trees affected by the disease include swamp bay, scrub bay, sassafras, and avocado. The first diseased avocado tree was discovered in 2011 in Dade County. The avocado growers are freaking out as this could be the end of avocados in Florida and possibly the Caribbean region. Think they are expensive now? They grow in California, so you’ll be able to pay shipping for them.
In all, we had a great time. The biologists got to practice their Latin, we hiked through beautiful woods, saw impressive geological features, learned lots of stuff, and there were no mosquitoes. We give a big thanks to Karie, Rob, and all the biologists for combining a fun hike with an educational outing.
Story by Tom Morris
Photos by Dave Wilson