Tied island facts for kids
A tied island is a special kind of landform where an island is connected to the mainland by a thin strip of land. This natural bridge is called a tombolo. Imagine an island close to the coast, and over many years, sand and gravel build up in the water between them, creating a permanent walkway.
This happens because the island acts as a shield against waves. The water behind the island is calmer, which allows sand and other materials carried by the ocean currents to settle and build up. Eventually, this pile of sand grows so much that it connects the island to the shore.
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How Tied Islands Are Formed
The key to a tied island is the formation of its connector, the tombolo. A tombolo is a type of isthmus, which is any narrow piece of land connecting two larger landmasses.
Here is how it usually happens:
- Wave Action: Waves bend and slow down as they pass an island.
- Deposition: As the waves slow down, they lose energy and drop the sand and sediment they are carrying in the calm water behind the island.
- Building a Bridge: Over hundreds or even thousands of years, this deposited material builds up to form a sandy or gravelly ridge that links the island to the mainland.
Some tombolos might be covered by water during very high tides, but for a landform to be called a tied island, the connection is usually permanent and above sea level.
Famous Examples Around the World
Tied islands can be found all over the globe. They are fascinating examples of how coastlines are constantly changing.
Europe
- St Ninian's Isle, Scotland: Located in the Shetland Islands, this is a classic example of a tied island. It is connected to the main Shetland island by a beautiful sandy tombolo.
- Isle of Portland, England: This is a famous example, but some geographers have a different idea about it. They think the connector, Chesil Beach, is a barrier beach that moved over time to touch the island, rather than a tombolo that grew out from it.
- Howth Head, Ireland: Located near Dublin, this large headland was once an island.
North America
- Coronado, California, USA: This popular city is located on a tied island connected to the mainland by a tombolo known as the Silver Strand.
- Nahant, Massachusetts, USA: This town is situated on a rocky tied island connected to the city of Lynn by a tombolo.
Asia
- Mount Hakodate, Japan: The mountain that overlooks the city of Hakodate was once an island. A tombolo formed and connected it to the larger island of Hokkaido, and the city was built on this sandy strip.
- Cheung Chau, Hong Kong: This popular island is actually two smaller islands that have been joined together by a tombolo.
See also
- Presque-isle (a French name that means "almost an island")
- Peninsula
- Tidal island
