Beaches can be made of different materials such as sand, rock fragments,and seashell fragments. Most beaches are made of resisitant minerals. Hawaii has black sand made of basalt,their green sand is made of the mineral olivine. While Jamaica's white sand is made of coral and shell pieces. Sand is carried down beaches by shore currents.
Sand also moves via storms and wind.
So, beaches are fragile features, that can be damaged by storms and human activities. Barrier islands are sand deposits that parallel the shore, though they seperated from the mainland. The islands start as underwater sand ridges. Hurricanes and storms add sediment and raise sea level. When the barrier island is exposed, the loose sand is blown into dunes by wind, which keeps the island above water.