A tombolo (Italian, from Latin tumulus – mound) or sometimes ayre (Old Norse Eyrr – gravel beach) is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island. Several islands tied together by bars which rise above the water level is called a tombolo cluster.^[1] Two tombolos form an enclosure called a lagoon that might eventually fill with sediment.