Barrier islands protect the mainland by taking the bulk of the wrath from hurricanes and other coastal storms. Although barrier islands lie parallel to the coast surrounding the country, they are always changing due to the movement of the sand by waves, wind, tides, currents and storms. The general movement of the sand parallel to the coast is called longshore drift. Long shore drift is generated by the action of waves and currents, usually from north to south. As a wave breaks and washes up along the beach, it meets the beach at an angle. The return of the water back to the ocean carries sand particles out to sea.
Barrier islands form when ocean waves, tides and wind act together to pile up sediment on shorelines. This creates large dunes which are then stabilized by vegetation. When sea level rises, these dunes are partly submerged and cut off from the shore, creating an island.
Barrier islands are dynamic – they are constantly being eroded and reshaped by water movement and sediment deposition. On the east coast, the coastlines are exposed to currents moving north to south, parallel to the coast. These currents erode the northern ends of the island while building up the southern end. This gives the island a drumstick shape.
The current barrier islands off the Atlantic coast are largely the result of melting global ice sheets and increasing sea level over the past 18,000 years. Off the coast of Georgia, amplified tides have led to the development of larger wider barriers.