How is a barrier island formed?

A barrier island is formed primarily when an active delta is abandoned. This process occurs as sediment builds up in a river delta, and when the delta becomes inactive due to changes in water flow or sediment supply, the accumulation of sediments can create a barrier island. These islands serve to protect the mainland from waves and storms and are often located parallel to the coast.

The formation of a barrier island through the abandonment of an active delta is a natural geological process influenced by sediment deposition and changes in hydrology. Over time, the shifting of currents and sediment sources influences the landscape, leading to the formation of these islands.

Other options, while they may influence coastal geology in other ways, do not directly contribute to the formation of barrier islands. Rising sea levels can lead to the flooding of coastlines but do not create barrier islands themselves. Volcanic activity primarily creates landforms such as islands or mountains rather than barrier islands. Human land reclamation efforts can alter coastal landscapes but do not represent the natural processes that typically lead to the creation of barrier islands.