A tombolo is a sandy or shingle isthmus. It is a deposition

landform A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given terrain, and their arrangement ...

by which an island becomes 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. The word ''tombolo'' is from the Italian ', meaning 'pillow' or 'cushion', and sometimes translated incorrectly as '' ayre'' (an ayre is a shingle beach of any kind). Several islands tied together by bars which rise above the water level are called a tombolo cluster. Two or more tombolos may form an enclosure (called a

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

) that can eventually fill with sediment.

Formation

The shoreline moves toward the island (or detached breakwater) owing to the accretion of sand in the lee of the island, where wave energy and longshore drift are reduced and therefore deposition of sand occurs.

Wave diffraction and refraction

True tombolos are formed by wave refraction and

diffraction Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation ...

. As waves near an island, they are slowed by the shallow water surrounding it. These waves then bend around the island to the opposite side as they approach. The wave pattern created by this water movement causes a convergence of longshore drift on the opposite side of the island. The beach sediments that are moving by lateral transport on the lee side of the island will accumulate there, conforming to the shape of the wave pattern. In other words, the waves sweep sediment together from both sides. Eventually, when enough sediment has built up, the beach shoreline, known as a spit, will connect with an island and form a tombolo.

Unidirectional longshore drift

In the case of longshore drift due to an oblique wave direction, like at Chesil Beach or

Spurn Head Spurn is a narrow sand tidal island located off the tip of the coast of the East Riding of Yorkshire, England that reaches into the North Sea and forms the north bank of the mouth of the Humber Estuary. It was a spit (landform), spit with a s ...

, the flow of material is along the coast in a movement which is not determined by wave diffraction around the now tied island, such as the Isle of Portland, which it has reached. In this and similar cases like

Cádiz Cádiz ( , , ) is a city in Spain and the capital of the Province of Cádiz in the Autonomous communities of Spain, autonomous community of Andalusia. It is located in the southwest of the Iberian Peninsula off the Atlantic Ocean separated fr ...

, while the strip of beach material connected to the island may be technically called a tombolo because it links the island to the land, it is better thought of in terms of its formation as a spit, because the sand or shingle ridge is parallel rather than at right angles to the coast.

Morphology and sediment distribution

Tombolos demonstrate the sensitivity of shorelines. A small piece of land, such as an island, or a beached shipwreck can change the way that waves move, leading to different deposition of sediments.

Sea level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

may also contribute to accretion, as material is pushed up with rising sea levels. Tombolos are more prone to natural fluctuations of profile and area as a result of tidal and weather events than a normal beach is. Because of this susceptibility to weathering, tombolos are sometimes made more sturdy through the construction of roads or parking lots. The sediments that make up a tombolo are coarser towards the bottom and finer towards the surface. It is easy to see this pattern when the waves are destructive and wash away finer grained material at the top, revealing coarser sands and cobbles as the base.

Examples

* Aupōuri Peninsula, New Zealand * Barrenjoey Headland, Pittwater,

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

, Australia * Beavertail Point, Conanicut Island,

Rhode Island Rhode Island ( ) is a state in the New England region of the Northeastern United States. It borders Connecticut to its west; Massachusetts to its north and east; and the Atlantic Ocean to its south via Rhode Island Sound and Block Is ...

, United States * Biddeford Pool,

Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...

, United States * Bijia Mountain, China * Broulee Island, New South Wales, Australia * Bruny Island,

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

, Australia * Burgh Island,

Devon Devon ( ; historically also known as Devonshire , ) is a ceremonial county in South West England. It is bordered by the Bristol Channel to the north, Somerset and Dorset to the east, the English Channel to the south, and Cornwall to the west ...

, England *

, Andalucía, Spain * Cana Island,

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

, United States * Chappaquiddick Island,

Martha's Vineyard Martha's Vineyard, often simply called the Vineyard, is an island in the U.S. state of Massachusetts, lying just south of Cape Cod. It is known for being a popular, affluent summer colony, and includes the smaller peninsula Chappaquiddick Isla ...

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

, United States * Charles Island,

Connecticut Connecticut ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Rhode Island to the east, Massachusetts to the north, New York (state), New York to the west, and Long Island Sound to the south. ...

, United States * Chausey,

Manche Manche (, ; Norman language, Norman: ) is a coastal Departments of France, French ''département'' in Normandy (administrative region), Normandy on the English Channel, which is known as , literally "the sleeve", in French. Manche is bordered by ...

département, France (two features connecting the main island and two smaller outcrops) * Chesil Beach, Portland,

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

, England * Cheung Chau,

Hong Kong Hong Kong)., Legally Hong Kong, China in international treaties and organizations. is a special administrative region of China. With 7.5 million residents in a territory, Hong Kong is the fourth most densely populated region in the wor ...

Crimea Crimea ( ) is a peninsula in Eastern Europe, on the northern coast of the Black Sea, almost entirely surrounded by the Black Sea and the smaller Sea of Azov. The Isthmus of Perekop connects the peninsula to Kherson Oblast in mainland Ukrain ...

Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...

* Eaglehawk Neck,

, Australia * S'Espalmador, Formentera, Spain * Fingal Bay, New South Wales, Australia * The

Rock of Gibraltar The Rock of Gibraltar (from the Arabic name Jabal Ṭāriq , meaning "Mountain of Tariq ibn Ziyad, Tariq") is a monolithic limestone mountain high dominating the western entrance to the Mediterranean Sea. It is situated near the end of a nar ...

* Grand Island National Recreation Area,

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

, United States * Grótta, Seltjarnarnes, Iceland * Guanarteme, Las Palmas de Gran Canaria,

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

, Spain * Gugh, St Agnes,

Isles of Scilly The Isles of Scilly ( ; ) are a small archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, Isles of Scilly, St Agnes, is over farther south than the most southerly point of the Great Britain, British mainla ...

, England * Gwadar,

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

* Hakodate,

Hokkaido is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...

, Japan * Howth Head,

Dublin Dublin is the capital and largest city of Republic of Ireland, Ireland. Situated on Dublin Bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, and is bordered on the south by the Dublin Mountains, pa ...

, Republic of Ireland * Inishkeel Island, Narin, Republic of Ireland * Kapıdağ Peninsula, Balıkesir, Turkey * Konet Island, Kuala Sungai Baru, Malacca, Malaysia * Kurnell,

Sydney Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...

, New South Wales, Australia * Lake Pomorie,

Bulgaria Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is situated on the eastern portion of the Balkans directly south of the Danube river and west of the Black Sea. Bulgaria is bordered by Greece and Turkey t ...

* Langness, Derbyhaven, Isle of Man * Little Heart's Ease, Newfoundland and Labrador beach,

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

, Canada *

Llandudno Llandudno (, ) is a seaside resort, town and community (Wales), community in Conwy County Borough, Wales, located on the Creuddyn peninsula, which protrudes into the Irish Sea. In the 2021 United Kingdom census, 2021 UK census, the community � ...

, North

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

* Louds Island at Muscongus Bay,

, United States * Maharees, Dingle Peninsula, Republic of Ireland *

Mare Island Mare Island (Spanish language, Spanish: ''Isla de la Yegua'') is a peninsula in the United States in the city of Vallejo, California, about northeast of San Francisco. The Napa River forms its eastern side as it enters the Carquinez Strait junc ...

, Vallejo,

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, United States * Maria Island, Tasmania, Australia * Maury Island, Washington, United States * McMicken Island State Park, Washington, United States * Miquelon, Saint-Pierre and Miquelon, France * Monemvasia, Laconia,

Peloponnese The Peloponnese ( ), Peloponnesus ( ; , ) or Morea (; ) is a peninsula and geographic region in Southern Greece, and the southernmost region of the Balkans. It is connected to the central part of the country by the Isthmus of Corinth land bridg ...

, Greece * Monte Argentario,

Tuscany Tuscany ( ; ) is a Regions of Italy, region in central Italy with an area of about and a population of 3,660,834 inhabitants as of 2025. The capital city is Florence. Tuscany is known for its landscapes, history, artistic legacy, and its in ...

, Italy * Mont-Saint-Michel,

Normandy Normandy (; or ) is a geographical and cultural region in northwestern Europe, roughly coextensive with the historical Duchy of Normandy. Normandy comprises Normandy (administrative region), mainland Normandy (a part of France) and insular N ...

, France * Mount Maunganui, New Zealand * Mount Taipingot, Rota, Northern Marianas * Nahant, Massachusetts, United States (a natural tombolo, but connected to the mainland by a

causeway A causeway is a track, road or railway on the upper point of an embankment across "a low, or wet place, or piece of water". It can be constructed of earth, masonry, wood, or concrete. One of the earliest known wooden causeways is the Sweet T ...

) * Nissi beach, Ayia Napa, Cyprus * Nusa Dua,

Bali Bali (English:; Balinese language, Balinese: ) is a Provinces of Indonesia, province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller o ...

, Indonesia * Ormara,

* Palisadoes, Kingston, Jamaica * Pangandaran,

West Java West Java (, ) is an Indonesian Provinces of Indonesia, province on the western part of the island of Java, with its provincial capital in Bandung. West Java is bordered by the province of Banten and the country's capital region of Jakarta to t ...

, Indonesia * Peniche, Portugal * Peniscola, Castellon, Spain * Presque Isle, Michigan, United States * Presqu'ile de Giens, Hyères, France * Presqu'ile Provincial Park,

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

, Canada * Quiberon, France * Ras Hafun,

Somalia Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...

* Sainte-Marie,

Martinique Martinique ( ; or ; Kalinago language, Kalinago: or ) is an island in the Lesser Antilles of the West Indies, in the eastern Caribbean Sea. It was previously known as Iguanacaera which translates to iguana island in Carib language, Kariʼn ...

, France * Scotts Head,

Dominica Dominica, officially the Commonwealth of Dominica, is an island country in the Caribbean. It is part of the Windward Islands chain in the Lesser Antilles archipelago in the Caribbean Sea. The capital, Roseau, is located on the western side of t ...

* Seongsan Ilchulbong in

Jeju Province Jeju Province (; ), officially Jeju Special Self-Governing Province (Jeju language, Jeju: ; ), is the southernmost Provinces of South Korea, province of South Korea, consisting of eight inhabited and 55 uninhabited islands, including Marado, Udo ...

, South Korea * Sharp Island,

Sai Kung District Sai Kung District is one of the districts of Hong Kong, 18 districts of Hong Kong. The district comprises the southern half of the Sai Kung Peninsula, the Clear Water Bay Peninsula in the New Territories and a strip of land to the east of Ko ...

, Hong Kong * Silver Strand (San Diego),

Coronado, California Coronado (Spanish language, Spanish for "Crowned") is a resort town, resort city in San Diego County, California, United States, across San Diego Bay from downtown San Diego. It was founded in the 1880s and incorporated in 1890. Its population ...

, United States * St Michael's Mount,

Cornwall Cornwall (; or ) is a Ceremonial counties of England, ceremonial county in South West England. It is also one of the Celtic nations and the homeland of the Cornish people. The county is bordered by the Atlantic Ocean to the north and west, ...

, England * St Ninian's Isle,

Shetland Shetland (until 1975 spelled Zetland), also called the Shetland Islands, is an archipelago in Scotland lying between Orkney, the Faroe Islands, and Norway, marking the northernmost region of the United Kingdom. The islands lie about to the ...

, Scotland *

Sveti Stefan Sveti Stefan ( Montenegrin and Serbian: Свети Стефан, ; lit. "Saint Stephen") is a town in Budva Municipality, on the Adriatic coast of Montenegro, approximately southeast of Budva. The town is known for the Aman Sveti Stefan resort ...

, near

Budva Budva (Cyrillic script, Cyrillic: Будва, or ) is a town in the Coastal Montenegro, Coastal region of Montenegro. It had 27,445 inhabitants as of 2023, and is the centre of Budva Municipality. The coastal area around Budva, called the Budv ...

, Montenegro * Tombolo at Dogashima in Japan * Vatersay,

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

– the island comprises two sections connected by a broad tombolo * Zhifu Island, Yantai, China Some of these may be simple isthmuses, and not have the deposition creation that defines a true tombolo.

Image gallery

File:Tombolo St Ninians 5940.JPG, The tombolo connecting St Ninian's Isle with the Shetland Mainland File:Laguna di Orbetello.JPG, Monte Argentario,

, Italy File:ChesilBeach.JPG, Chesil Beach, seen from the Isle of Portland looking towards mainland

File:Angel Road Shodo Island Japan01s3.jpg, The Angel Road of Shōdoshima, Japan File:Evening view from the Mount over Mount Maunganui.jpg, Looking south from the summit of Mount Maunganui, New Zealand, to the city of Tauranga File:2010-10-01 02-27-36 DSC 0354 Boris.jpg, The eastern end of Bennett Island with its glaciated tombolo in the background File:Gwadar satellite view.jpg, Satellite view of Gwadar, Pakistan File:Aerial view of Dublin 2.JPG, An aerial photo of the isthmus of Sutton which connects Howth Head and

County Dublin County Dublin ( or ) is a Counties of Ireland, county in Republic of Ireland, Ireland, and holds its capital city, Dublin. It is located on the island's east coast, within the Provinces of Ireland, province of Leinster. Until 1994, County Dubli ...

References

External links

Geology.About.com's page on tombolos
(useful for its descriptive photograph)
Tombolo in Sainte-Marie, Martinique
(useful for its photos and description)
further reading on Detached breakwaters from Vlaams Instituut voor de Zee in Belgium

further reading on coastal structures from Prof. Leo van Rijn in Holland
{{coastal geography Coastal and oceanic landforms Coastal geography Tombolo Oceanographical terminology