The Sandy Blackwater River (Earthcache) EarthCache
The Sandy Blackwater River (Earthcache)
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Located on the sandy shoreline of the Blackwater River in the Blackwater River State Park. A short walk along dirt and wooden pathways.
As of 10/2009 there is a $4 charge for parking/entrance.
The Blackwater's soft sandy bottom and large sandbars are a sharp contrast to the dark tannic water that gives the river its name. The Blackwater River is the ONLY pristine sand river left in the United States - so unique that the State of Florida purchased and designated it as a State Forest. The Blackwater State Park was certified a Registered State Natural Feature in 1980, for possessing exceptional value in illustrating the natural history of Florida. The average depth of the Blackwater River is 2 ½ feet, average speed is 5 miles per hour (no white water). You may notice a similarity of the soft, sugar-white sandbars to the snow white beaches of the Emerald Coast - it's the quartz sand!
Not All Sand Is the Same
Sand in Hawaii is black from pulverized lava rock. In Bermuda, it's pink from the weathering of coral reefs. Some beaches are called "cobble beaches" and aren't sandy at all, but rather are made up of pebbles and rocks (going barefoot on these beaches can hurt!). Florida's coastline is 60 percent sand and varies in its origin and consistency. Just south of St. Augustine, coquina rock from tiny clam deposits makes up the shoreline. Sand in the Keys comes from weathered coral reefs. The shoreline along the Big Bend Gulf Coast north of Tampa and along the very tip of South Florida is made of clay rather than sand. Much of the rest of Florida's sandy coastline is made of calcium carbonate and quartz. The calcium carbonate comes from marine plants and animal shells and skeletons that have been crushed into sand. On the Florida Gulf beaches, quartz sands are found on the more northern beaches and a mix of quartz and calcium carbonate sands are found as you move south along the Gulf coast.
Quartz Sand
Pure silica sand (quartz sand) is what glass is made of.
Silica sand is used by sand blasters because of its hardness and resistance to abrasion.
The easiest way to tell if the sand is pure quartz or silica sand is to mix some pure water with the sand and then measure the pH. If the pH = 7, then you have quartz sand without contamination by calcium carbonate sand.
Here's a piece of interesting information: If you add a bit of vinegar to calcium carbonate sand, the carbonates will react with the vinegar and will eventually make the sand disappear.
Blackwater's Quartz Sandy Bottom
The Blackwater River is known for its soft, sandy bottom. Composed of pure quartz crystal this quartz sand began in the Appalachian Mountains. Quartz sand comes from igneous rock, the kind of rock that once was molten. The most common such substance in quartz is granite, like that of the Appalachian Mountains. Those quartz grains are very fine, without any coral or shell fragments, which results in sand with a soft, flour-like texture. Wind, rain, frost and dissolved carbon dioxide reacting with these granite mountains cause them to break down. Mechanical crushing from earthquakes, glaciers and rock slides further breaks up larger particles. Smaller pieces are then move by wind, water or ice and travel to rivers or lakes to become sand dunes, sand bars and beaches. The sand from the Appalachian Mountains took a trek through rivers, pools, swamps and the bays until it finally accumulated creating the sand bars along the Blackwater's bends and bottom. The sand from the Blackwater River eventually traveled, and continues to travel, all the way south to the edges of the emerald waters of the Gulf of Mexico to Santa Rosa and Pensacola Beach Islands. At the end of its journey it is so fine in texture, it literally squeaks under your toes! The sand also helps our beaches from heating up like an oven in the Summer time, unlike other beaches with darker and coarser sand.
To Log:
Post a short paragraph telling about your trip to the Blackwater River area and with your log post a picture of you (and your GPS) with the Deaton Bridge, the Blackwater and a sandbar in the background (there's a tricky task for you).
Send answers to the following questions to me via my profile; do not put the answers in your cache log.
1. Why do you suppose the sand squeaks when you walk on it?
2. Do you believe that the Blackwater sand will disappear in vinegar?
3. While in the area of the river, notice the location of the sandbars. You'll see a common aspect, they are all on the inside of the river's bends. Why do you think the large sand deposits are always in this location?
4. What will eventually happen to the sand currently on the bottom of the Blackwater?
Refereces:
Beaches to Rivers; Santa Rosa FAQ: (visit link)
Naples Florida Weekly:
(visit link)
Additional Hints
(No hints available.)