A Quick Chemistry Lesson
Sodium Chloride (NaCl) is the result of a chemical bonding that occurs between the metal atoms of sodium and chlorine. All atoms with incomplete electron valence shells have a need to fill their outer shells and can bond with other atoms, under the right conditions. Chlorine has 7 electrons in its outer valence shell and only needs 1 more electron to complete its outer shell. Conversely, sodium has only 1 electron in its outer valence shell and still needs 7 more electrons to complete its shell. Thus, when sodium and chlorine come into contact, the conditions are right to fill one another’s outer valence shells. It is easier to transfer 1 electron than 7, so the extra electron from sodium moves into the outer valence shell of chlorine, completing both electron shells and chemically bonding the two atoms together. The element resulting from the chemical bonding, sodium chloride, is more commonly referred to as salt and is the object of interest in pursuit of this EarthCache.
Salty Marsh
The Castaway Island preserve is one big salt marsh. The element that sets the preserve apart from its local surrounding is, of course, SALT!!!!
Ocean water has a salinity level (salt % level) between 3-5 percent. Conversely, fresh water has a salinity level of only .05% or less. The river flowing through the park connects to the Atlantic Ocean, just a couple of miles away, and creates brackish water with a salinity level between that of fresh water and ocean water. As the tide moves in and out the river, salt water is brought in from the ocean several times each day. At the lowest elevations in the park, the salt has a chance to settle deep into the soil, creating a higher level of salinity (% of salt). Conversely, at higher elevations in the park, there is less chance for the tides to bring in the salt and, therefore, less salinity in the soil. The growth of the entire ecosystem starts with the ability of the plants residing in the area to thrive in the salty conditions.
Fulfilling the Requirements
The Sodium Chloride (NaCl) EarthCache is located in Castaway Island Preserve, open daily from 7 AM - sunset. The entire EarthCache can be completed without ever leaving the designated trails. All stages of the cache are fully wheel chair accessible and kid friendly, so load the family in the car and come learn a little bit about the Castaway Island Preserve salt marsh. Just remember, take everything you learn “with a grain of salt”!
Stage 1: Proceed to the following coordinates along the boardwalk: N 30 17.897 W081 25.846, which are accessible from the paved walking trail near the starting point of the EarthCache. You will see an informational sign educating visitors about the salt marsh. Using the informational display, email the cache owner the answers to the following questions:
1. Why are there so few plants and why do they grow this way?
2. What is the predominant grass of the marsh and why?
3. Tidal movement often creates low berms and islands that support ___________?
4. Look around at the area of the salt marsh you are standing in: Are you located nearer to a high tide region or low tide region? Does that mean the salinity in the soil is high or low compared to the majority of the preserve? (Hint: Stage 2 is a good representation of the majority of the preserve).
Stage 2: Proceed to the following coordinates: N 30 17.903 W 081 25.822 at the end of the boardwalk. Face east and look out across the preserve. Keep in mind what was learned at stage 1 and email the cache owner the answer to the following question:
5. Are you looking out on a high tide region or low tide region? Does that mean the salinity in the soil is high or low compared to the area observed at stage 1?
Optional: Take a picture of your favorite location in Castaway Island Preserve and post the picture with your log entry.
Summary: To claim credit for this EarthCache you will need to email your answers to the questions from stage 1 and stage 2 to the owner of the cache at the time of posting. Additionally, you are encouraged to upload an OPTIONAL picture of your favorite place in the park with your log entry. Log entries that are not accompanied by an email to the cache owner with the answers to the above questions will be deleted.
Sources:
Carpi, A., Ph.D. 2003. “Chemical Reactions,” Visionlearning Vol. CHE-1 (6) Retrieved from Vision Learning
Florida Natural Areas Inventory and Florida Dept. of Natural Resources. 1990. Guide to the natural communities of Florida. Florida Natural Areas Inventory and Florida Dept. of Natural Resources, Tallahassee, FL. Retrieved from Florida Dept. of Natural Resources
Percy, J.A. 2000. Salt Marsh Saga Conserving Fundy’s Marine Meadows. Sea Pen Communications. Retrieved from Bay of Fundy
Special Thanks to City of Jacksonville Waterfront Management and Programming Department for granting permission to publish this EarthCache in the Castaway Island Preserve.