Barrier islands were likely formed at the end of the last Ice Age, around 18,000 years ago. Popular theory suggests that melting glaciers caused sea levels to rise and flood areas inside the beach ridges. The sea carried and deposited sediment just outside the new coastlines in the shallow waters. Sediment continued to build up with incoming waves and currents. Rivers flowing from the mainland also carried sediment. This buildup of sand and sediment eventually formed small islands just off the coasts.
These small islands perform valuable functions that include protecting the coasts from damage caused by severe weather and providing animal habitats.
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