Tombolo

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Tombolo at Stockton Island, Apostle Islands, Wisconsin.

Satellite view of Chesil Beach (shown as a long blue line) in Dorset, England (Landsat image viewed using NASA World Wind software)

Ap Lei Pai (left), an islet connected to Ap Lei Chau (right), a bigger island, in the southern waters in Hong Kong.

This diminutive tombolo, of less than ten metres length, connects the island of Fjärdholmen in the Stockholm Archipelago with an outlying rock at 59°29′21″N 18°49′53″E / 59.48925°N 18.8314°E

For the Italian city, see Tombolo, Italy.

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. They usually form because the island causes wave refraction, depositing sand and shingle moved by longshore drift in each direction around the island where the waves meet. Eustatic sea level rise may also contribute to accretion as material is pushed up with rising sea levels. This is the case with Chesil Beach (which connects the Isle of Portland to Dorset in England), notable because the shingle ridge is parallel rather than perpendicular to the coast.