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Ever wonder how Rockledge, Florida got it's name? It was named for the Atlantic Coastal Ridge that passes through the town and was quarried to provide stone for places like the jetties at Sebastian Inlet State Park. During this earthcache you will visit the last section of the Addison/Ellis Canal where construction ground to a halt as equipment broke down trying to cut through the dense coquina limestone of the Atlantic Coastal Ridge. Find out why this failure was a lucky break for the environment. Then you will continue on to a coquina quarry to examine the geological layers revealed in the cut stone and look for solution holes. This earthcache includes 5 stages and 7 questions. Please email your answers to the questions before posting a log for this cache. Your answers should not be posted in your online log, but feel free to post as many pictures as you want. Don't forget to bring plenty of water and bug spray for the hike.
As you begin this earthcache, please sign in at the desk just outside the Visitor Center. This helps the park document how many visitors they have so they can qualify for funding. Follow the signs to the Coquina Trail which will take you on a short climb up onto the Atlantic Coastal Ridge.
Stage 1: Atlantic Coastal Ridge (N 28 32.108 W 80 48.056)
The Atlantic Coastal Ridge extends along the eastern coast of Florida as a low ridge of sand over coquina limestone. It ranges in altitude from 10 to 50 feet above sea level. This desert-like scrub is vital as a recharge area for the aquifer. Water drains down through the layers of sand and coquina to replenish the fresh water supply. If the area was developed and paved, less water would trickle down into the aquifer. As more people move into Titusville and the surrounding area, a greater demand is placed on the aquifer and the fresh water supply becomes limited. But another invisible threat lies deep in the ground. As the water level drops in a fresh water aquifer, salt water can intrude and contaminate the water. Salt water intrusion is the result of differences in hydrostatic pressure.
Hydrostatic pressure is the pressure coming from the weight of the water. It's value is directly proportional to the depth of the water in the aquifer and to it's density. Salt water is heavier than fresh water because the salt particles give it a higher density. The hydrostatic pressure under a body of saltwater is higher than the pressure under freshwater. When a freshwater aquifer is close to a source of salt water like the Indian River Lagoon or the Atlantic Ocean, there can be underground cracks and caves that connect them. As the water level drops in a freshwater aquifer, the hydrostatic pressure is reduced. Water from the Indian River Lagoon or the Atlantic Ocean is pulled into the fresh water aquifer until the pressure equalizes.
Question 1. What is your elevation at stage 1?
Question 2. Describe the soil on this section of the trail.
Stage 2: Mesic Hammock (N 28 32.105 W 80 48.006)
Mesic Hammocks have a closed forest canopy. The soil in this area tends to be moist and clayey because of the dense tree litter and humid conditions that prevail under the tree canopy. The Mesic Hammocks tend to shed their rainfall through surface water runoff.
Question 3: What is your elevation at stage 2?
Question 4: Compare the soil on this section of the trail with what you observed at stage 1. Do you think the Mesic Hammock would be an important recharge area for the aquifer?
Stage 3: Sign-The Addison/Ellis Canal (N 28 32.085 W 80 48.126)
The Addison/Ellis Canal was probably dug in 1912-1913 with equipment left from the Panama Canal Project. The canal would be used to drain marshland in the St Johns River Valley and make way for agriculture and land development. Others think it was meant to be a waterway connecting the St. Johns River to the Indian River. Beginning just east of the St Johns River, the canal’s course made easy progress through the marshland and sand ridges. It met it's fate in the Enchanted Forest. The coquina rock of the Atlantic Coastal Ridge, which goes north-south through the center of the forest, proved to be an insurmountable obstacle. The canal never reached a useful depth and construction ended just east of the ridge in Addison Creek. What remains is a 20-30 foot gorge with a small stream at the bottom. The layers of stratification in the gorge reveal valuable information about the formation of the Coquina ridges and dunes.
Question 5: What impact did the canal have on the flow of water in the Enchanted Forest?
Stage 4: Coquina Rock in the Butterfly Garden (N 28 32.010 W 80 48.167)
Find the sign telling about Coquina Rock.
Question 6: What causes Solutions holes in Coquina Rock?
Stage 5: The Quarry (N 28 31.699 W 80 47.977)
The coquina rock within the Enchanted Forest is estimated to be late Quaternary (120,000 years old). The Quarry is an excellent place to view the layers of stratification that form in coquina rock. If you look closely, you will see shells embedded in the stone. Notice how the texture varies between the different layers. In some places the coquina formed very solidly and in other places it is softer and subject to more erosion. In other areas, it didn't form into rock at all leaving little caves where sand washed out during the digging of the Quarry. This particular area has several good examples of solution holes.
Question 7: Look for the solution holes in the wall of the rock quarry and estimate the diameter of the largest one you can find.
References
Addison/Ellis Canal http://www.nbbd.com/godo/ef/canal/index.html
Florida Geology http://www2.fiu.edu/~whitmand/Courses/Fl_geo_notes.html
Brochure and Trail map http://www.eelbrevard.com/pubs/ef_brochure.pdf
Congratulations to MollyMap for First To Log!