If you were to pass by them, Norway's floating islands wouldn't warrant a second look. By all appearances, with a surface covered in green and sprinkled with trees, they betray little of their true nature from afar. It's only when you attempt to step on one or, as shown in the video above, view them over time, that you notice something odd.

While bizarre, the phenomenon of floating islands is fairly common around the world. Composed of aquatic plants, mud, and other detritus, they're generally capable of supporting not only a varied aquatic community below, but also small trees and species above. They tend to form when plants like cattails or reeds extend out into deeper water and are torn loose from shore by storms. Some have been known to last only a season, while others endure for decades or longer.

As one commenter on Reddit shared, floating islands also make extremely interesting formations to explore.

"Dove beneath one of these a few years ago, and it's structurally kinda similar to an iceberg," the commenter wrote. "The one I went beneath was probably around 2.5-3 meters below the surface, with only about 20 cm above. It was not connected to the bottom, so me and my friends swam behind it and could freely move it wherever we wanted. It also had long roots hanging off its underside."

Historical curiosities

A floating island in Posta Fibreno lake, Italy. A floating island in Posta Fibreno lake, Italy. (Photo: Piero "Positivo" Quadrini/Wikimedia Commons)

While floating islands are commonly found in freshwater sites, there are also a few recorded instances of these unusual masses showing up at sea. In 1924, Capt. Jonas Pendelbury of the Dollar Line steamship "President Adams" encountered no fewer than 10 floating islands off the coast of Borneo, as this image of a New York Time article reveals. Surprisingly, they were teeming with life.

Captain Pendelbury encountered the biggest of the floating islands first. He said its palm trees were higher than the wireless masts of his ship and in their tips were chattering monkeys and singing birds. Through marine glasses the skipper said he saw great masses of flowering vegetation and a large number of cobras, deadly reptiles.

Other sailors, such as in this account from 1908 in the Washington Post, visited what they thought was an island and only later realized their mistake.

After gathering the cocoanuts the sailors returned to the cruiser, which, oddly enough, seemed much further off, and considerably more to the southwest than when they left her. Then it just dawned on them that they had been visiting one of the floating islands so often heard about but seldom seen in the South Atlantic. Further observation confirmed the suspicion, as the cruiser remained near it long enough to see the island change its position.

Even today these floating phenomenon continue to capture the imagination, including this one from a completely different part of the world — a floating island an Argentinian swamp buoyed by methane,

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Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Time-lapse captures bizarre beauty of Norway's floating islands
Norway's floating islands, unusual masses of soil and spongy plant life, support a wide variety of species.