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Offshore bars (barrier bars or barrier islands) are deposits of sand, gravel, and pebbles which are completely detached from the land. Some barrier islands exhibit features suggesting that former spits were separated from the land by violent storms. Other barrier islands may have formed when a rising sea level caused the spit to become isolated. Still other deposits reveal that barrier islands are caused by wave action which erodes material from the sea floor and heaps the sand, gravel, and pebbles into ridges just above sea level.
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