Saturday, June 29, 2013

Apalachicola National Forest: Leon Sinks Geological Area (Blog Hike #407)

Trails: Sinkhole and Gumswamp Trails
Hike Location: Apalachicola National ForestLeon Sinks Geological Area
Geographic Location: south of TallahasseeFL (30.30951, -84.34610)
Length: 4.1 miles
Difficulty: 3/10 (Easy/Moderate)
Last Hiked: December 2012
Overview: An interesting hike featuring sinkholes and swamps.
Hike Route Map:
Photo Highlight:

Directions to the trailhead: From Tallahassee, drive south on US 319 7 miles to the signed entrance for Leon Sinks on the right.  Turn right to enter the area and drive the short entrance road to a nice blacktop parking area with newly constructed restroom facility and information kiosk.  Park here.

The hike: Extending from southern Tallahassee to the Gulf of Mexico, the Woodville Karst is one of Florida’s most interesting geological areas.  Like other karst formations, the Woodville Karst is characterized by an abundance of caves, springs, and sinkholes.  These landforms are created over many years as water dissolves the limestone bedrock, causing large chunks of the rock to collapse underground.  Most of the world’s major cave systems are found in areas with karst geology.
            Contained in the northeastern corner of Apalachicola National Forest, the Leon Sinks Geological Area protects one of the largest concentrations of sinkholes in the Woodville Karst.  The sinks themselves are accessed by the 2.5 mile appropriately named Sinkhole Trail.  The many interpretive signs along the way make the Sinkhole Trail a real-world outdoor classroom in karst geology.  In addition to the Sinkhole Trail, the 1.7 mile Gumswamp Trail takes hikers around a swampy area just south of the sinks.  This description combines both of these trails for the 4.1 mile grand tour of Leon Sinks.
Information kiosk at trailhead
            The hike begins at the large kiosk where the common entrance trail heads into the woods.  After less than 0.1 miles of level walking, the trail forks to form the loop.  This description will turn right and hike the loop counterclockwise, using the Sinkhole Trail as the outbound route and the Gumswamp Trail as the return route.  The white sandy-dirt trail heads north and crosses the first of several old logging roads.  The wide old logging roads look like trails, but all of these junctions are well-signed.  When in doubt, follow the numerous blue paint blazes marking the Sinkhole Trail.
Sandy-based Sinkhole Trail
            0.2 miles into the hike, you reach the first sinkhole, which is labeled Dry Sink on the ground and on the trail map.  This sink is nearly 20 feet deep, and as its name suggests there is no permanent water at its bottom.  Some steps built into the ground take the trail to the base of the sink and then back up.  The geology lesson begins as interpretive signs tell of the plants that live in the sink.  Dry Sink is the only sink that the trail passes directly through, so take some time to make observations in Dry Sink.
Entering Dry Sink
            After climbing out of Dry Sink, the trail assumes a meandering course as it passes several sinks one right after another.  The terrain at Leon Sinks is fairly flat except for the sinkholes, so the hiking is quite easy unless you choose to take a side trail into one of the sinks.  More old logging roads are crossed, but each of these crossings is well signed.
            At 0.6 miles, you reach the first wet sink, Hammock Sink.  Since every sink you have seen up to this point has been dry, the deep clear waters of Hammock Sink may surprise you.  Sinks can be wet or dry depending on how deep they fall into the ground.  Wet sinks plunge deep enough to penetrate the Floridan aquifer, a vast underground river that underlies most of Florida’s panhandle.  Dry sinks are dry because they are not deep enough to reach the aquifer.  Hammock Sink in particular is an entrance to an underwater cave system that has been shown to link to Wakulla Springs some 10 miles to the southeast.  A wooden overlook extends over the water, and abundant aquatic life can be seen in the clear waters.  Take a few minutes to see what you can see.
Hammock Sink
            Back on the main trail, the trail heads gradually uphill and passes Tiny Sink before leaving the slash and loblolly pine forest that has dominated thus far and entering a longleaf pine forest.  Longleaf pines are among the slowest growing pines on earth, but their long, deep roots make them among the hardiest pines on earth.  Many longleaf pines live to be several hundred years old.  While longleaf pines are built to survive natural enemies such as drought and wildfire, most have not survived the ax.  Last century longleaf pines were a favorite of Florida’s timber industry because their straight trunks make perfect masts for boats.  These pines used to cover large parts of Florida, but today very few patches of mature longleaf pines remain. In particular, this longleaf pine forest is less than 100 years old.
            0.9 miles into the hike, you reach Big Dismal Sink.  Big Dismal Sink is another wet sink, and a relatively new wooden overlook provides a great view of the cliff-lined body of water.  I heard some dripping while I stood on this overlook, and an interpretive sign told me that this is the sound of water dripping out of the sink and into the Floridan aquifer.  At over 130 feet deep, Big Dismal Sink is the largest sink at Leon Sinks, so take some time to admire the landform.
Big Dismal Sink
            In another 0.3 miles you arrive at Magnolia Sink, named for the large number of southern magnolias that grow along the sink’s rim.  Some unusual rock formations can also be found along the rim of Magnolia Sink.  Just past Magnolia Sink, the trail curves left and heads back through the swath of longleaf pine forest, soon to pass large and ominous Black Sink.
            Near 2 miles you reach the signed spur trail to Lost Stream Overlook.  This short spur leads to an overlook of Lost Stream Sink, so named because Fisher Creek flows in... but never flows out.  In fact water does flow out, but it flows out of the bottom of the sink into the underground Floridan aquifer.
Crossing Natural Bridge
            The main trail used to ford Fisher Creek below the sink, but now it has been rerouted to tread high on the cliffs above the sink.  Another 0.4 miles of meandering leads the Sinkhole Trail to Fisher Creek Sink.  The trail crosses Fisher Creek on a wide, large natural bridge (you might not even recognize it as a natural bridge if it were not signed as such) and reaches an intersection.  The white-blazed Crossover Trail continues straight and gives a shortcut back to the trailhead, but this hike will take the full tour by turning right to begin the Gumswamp Trail, which is marked with yellow paint blazes.
Fisher Creek Sink
            The Gumswamp Trail continues to head south.  After giving one last view of Fisher Creek Sink, the sinkhole section of the area is left behind for now, and quickly the trail enters into a slash and loblolly pine forest with a dense understory of saw palmetto.  Near the southern boundary of the area, the trail makes a sweeping left curve to reach Bear Scratch Swamp, the first of 3 small swamps.  The swamps feature standing water at normal water tables and a small cluster of bald cypress trees.  Whereas water up at the sinkholes has eroded through the limestone bedrock into the aquifer, down here the water remains on top of the intact bedrock.
Bear Scratch Swamp
            The trail passes two more swamps, South and Shadows swamps, before intersecting the east end of the Crossover Trail at 3.9 miles.  Continue straight at this intersection for the final leg back to the trailhead.  On its way, the trail passes Hutchison’s Spur to one final sink, Gopher Hole. Gopher Hole is a dry sink that looks like a small cave opening or, with a little imagination, like a large gopher hole.  At 4.05 miles, you close the loop.  A right turn and short walk down the entrance trail will return you to the information kiosk and complete the hike.
Gopher Hole

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