– How barrier islands are formed.
– About seashells.
Barrier islands that have been protected from development are wonderful places for families to find undisturbed backcountry. Some barrier islands have been designated national wildlife refuges. Others are national seashores.
Gradually, over millions of years, earth and rock from the continents washes away to the sea. At the mouth of a river, its sediment is deposited into a shallow, fan-shaped delta. Twice a day, tides flow into and out of estuaries, grinding pebbles and gravel into sand. The tide picks up where the river leaves off and carries sediment and sand into the sea. Waves push the sand along the coast, where it forms long, thin islets. These are called barrier islands because they form a protective barrier between the mainland and the open ocean. They shield the coast from the erosive power of the ocean waves, but the little islands themselves are constantly being reshaped and reformed by wave action. Barrier islands are always in movement, with sand being eroded away from one end and deposited on the opposite end.
A barrier island consists of three parts: the beach, the central forest, and a saltwater marsh on the inland side of the island. Wind and water pile beach sand into dunes, which are eventually stabilized by vegetation. So the beach becomes a forest dominated by pines. But gradually the entire island migrates and the forestland is eroded away. This process takes hundreds of years. Sometimes you will see “graveyards” of dead trees that will eventually be washed into the sea as the island changes shape.
Looking for barrier islands
Look at detailed maps of the East Coast and the Gulf Coast. You will see many barrier islands that stretch along the edge of the continent like a string of beads. They protect the mainland from ocean waves. The channel between the barrier islands and the mainland is known as the intracoastal waterway. You will see many more small craft traveling along the intracoastal waterway than out on the open ocean. Bridges connect some barrier islands to the mainland—either high bridges (high enough for boats to go under) or drawbridges, which stop cars and raise the roadway for a boat to pass through. Other islands float free, connected by car ferries (like Ocracoke Island in North Carolina’s Outer Banks) or by passenger ferries (like Georgia’s Cumberland Island). Other barrier islands are private, with no public transportation.
Exploring a barrier island
Select a barrier island that hasn’t been ruined by development. Most often this will be an island managed by a state government or the federal government. Take a hike on the beach, into the central forest, and along the saltwater marsh. Sea oats usually grow on sand dunes fronting the open ocean. They have long roots that stabilize the dunes by preventing sand from blowing away. Sea oats play a vital role in protecting beaches. They must never be stepped on or picked. Leave them to do their job. As you hike further inland, you might see a few sea oats there. That is evidence that this stabilized dune was once a beach in the not-too-distant past. From evidence like this scientists can tell many things about the world around us.
Because of the abundance of food in a coastal environment, you will see more wildlife on the seashore than anywhere else. When you go exploring you may come upon great numbers of birds when they are nesting. Stay far away and observe them through binoculars. If you see any signs of alarm, leave the area. When birds are frightened away from their nests, their eggs often fail to hatch.
Barrier islands make great places to look for shells. If you pick up a shell and find a mollusk alive inside, gently replace the shell the way you found it. We never take home live shells. Following are some of the shells you will find on a barrier beach in the Southeast.
Bivalve shells have two valves or shells hinged together. They dominate on sandy beaches because there is so much food available. Angel wings are beautiful bivalves that burrow down into the sand and mud of a beach. Atlantic surf clams are found in the intertidal zone where the surf is breaking. A sea pen looks like an old-fashioned quill pen made out of a feather. It is pointed at one end and then widens into a long flare.
Univalve shells have only one valve or shell. Members of this group include snails and conch shells. A channel whelk is a predator that feeds on bivalve mollusks. A knobbed whelk has a beautiful red interior and is the state shell of Georgia. When univalve shells are discarded by its mollusk, they become homes to other animals like hermit crabs.
Crabs also live on beaches. You might see a horseshoe crab, which is related to the scorpion. Its tail looks like it could sting, but it doesn’t. You might see a live horseshoe crab or you might find its empty shell.
Be sure to take your binoculars along to look at all the interesting things on a barrier island. Look high up in the branches of a dead tree. If you see a great big nest made out of sticks, it probably belongs to an osprey. Another name for the osprey is fish hawk. Can you guess why? What do you suppose it eats? You will also have fun watching shore birds such as terns and sandpipers. These birds find their food right at the edge of the surf.
Cumberland Island National Seashore, Georgia. The barrier islands off Georgia and the Carolinas are called “sea islands.” They were some of the first places to be settled in the South. During the 1700s, rice and indigo were grown on sea island plantations. A high-quality, long-staple cotton called sea island cotton was also grown here. Today some of the oldest, most traditional African-American communities in the country flourish on a few of these islands. Some of the older people can still speak Gullah, a Creole blend of English and several African languages such as Ibo, Hausa, and Yoruba.
Cumberland Island, however, had a somewhat different past. In the late 1800s much of the island was bought by Thomas Carnegie, brother of the famous steel magnate Andrew Carnegie. It served as a vacation home until the mansion was destroyed by fire in 1959. The property was donated to the National Park Foundation by the Carnegie family in 1971. Ruins of the mansion can still be seen. The only way to reach Cumberland Island is aboard a passenger ferry. (No cars allowed!)
The best seasons for backpacking are spring and fall, when insects aren’t a bother and temperatures are mild. You’ll surely encounter the island’s horse herd and perhaps loggerhead turtles, which come ashore to lay their eggs. Backcountry permits and ferry reservations are required. Numbers are strictly limited, and ferry reservations go fast. If you want to experience this remarkable island during peak season, you must finalize plans many months in advance. Information: Superintendent, Cumberland Island National Seashore, P.O. Box 806, St. Marys, GA 31558, (912) 882-4335.
Assateague Island National Seashore, Maryland, and Chincoteague National Wildlife Refuge, Virginia. These neighboring barrier islands are home to the famous wild ponies. On Assateague you can find walk-in (which means vehicle-free) seaside campsites. If you canoe, obtain a permit for one of the paddle-in campsites. There is no camping on Chincoteague, but it is also well worth a visit. Kids will be thrilled to see the fall migrations of tens of thousands of snow geese and brant (a small, dark goose) on their way south from the Arctic. A wildlife loop is open only to hikers and cyclists until 3 p.m. and to vehicles after that. The annual wild pony swim and auction is held the last week of July. Information: Superintendent, Assateague Island National Seashore, Berlin, MD 21811, (401) 641-1441.