Floating island

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This article is about the natural phenomenon. For floating island in fiction, see Floating island (fiction). For the dessert, see Floating island (dessert).

Uros island

A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from a few inches to several feet. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less commonly as a man-made phenomenon. Floating islands are generally found on marshlands, lakes, and similar wetland locations, and can be many hectares in size.

When they occur naturally they are sometimes referred to as tussocks, floatons, or sudds. Natural floating islands are composed of vegetation growing on a buoyant mat consisting of plant roots or other organic detritus.

They typically occur when growths of cattails, bulrush, sedge, and reeds extend outward from the shoreline of a wetland area. As the water gets deeper the roots no longer reach the bottom, so they use the oxygen in their root mass for buoyancy, and the surrounding vegetation for support to retain their top-side-up orientation^{[citation needed]}. The area beneath these floating mats is exceptionally rich in aquatic lifeforms. Eventually, storm events tear whole sections free from the shore, and the islands thus formed migrate around a lake with changing winds, eventually either reattaching to a new area of the shore, or breaking up in heavy weather.

Natural floating islands may have been the source of many "disappearing island" legends, such as those surrounding the Isle of Avalon.

Floating artificial islands are generally made of bundled reeds, and the best known examples are those of the Uros people of Lake Titicaca, Peru, who build their villages upon what are in effect huge rafts of bundled totora reeds. The Uros originally created their islands to prevent attacks by their more aggressive neighbours, the Incas and Collas. The Aztec capital, Tenochtitlan, was surrounded with chinampas, small artificial islands used for agriculture known as "floating gardens" (though not really floating). Spiral Island was a more modern one-person effort of constructing an artificial floating island in Mexico.

The British wartime Project Habakkuk proposed the construction of aircraft carriers made of ice-like Pykrete. Its size and speed made it more an artificial iceberg or island than a ship.