What is a Pseudo-Atoll?


If you are an experienced scientist, probably for you is very easy to distinguish the pseudo-atoll from the real atoll.

Perhaps, you are able to instantly see the difference without any special tools or scientific techniques.

For people without specialized scientific knowledge, however, the difference can be quite difficult and even impossible to find, at least in most cases.

Both types of tropical islands are divinely beautiful and equally irresistible, and they both bring equally strong feeling of pleasure to the human eye.

Real Atoll formation - French Polynesia
Real Atoll formation – French Polynesia by dany13

In both cases, the islands are home to a wide variety of species of corals as well as to large communities of fish and other sea creatures.

We omitted to say that we intentionally used the word “tropical” because both types of islands exist only in the tropical areas of the planet.

No matter if we are talking about real or pseudo-atolls, they require some specific environmental conditions which make the formation of atolls possible.

In both cases the islands need plenty of sunshine.

Another one of the most important factors is the sea water temperature, which should never drop below 18°C because this is the lowest bearable temperature for the warm-loving species of corals.

At the same time, the development of coral reefs and corals is the most important condition for the formation of both types of islands.

Of course, there are cold-water coral species that are able to withstand waters with lower temperatures.

However, the formation of this type of reefs we are talking about always requires thermophilic species of corals.

They in turn grow best when the sea water temperature is 23°C or higher.

ring-shaped atoll
Ring-shaped atoll by Kin Lane

In the case of pseudo-atolls above the surface of the ocean there is an island (or a number of islands) with a ring shape or shape that partially reminds of a ring, and actually, this is what misleads us.

The difference between the real atolls and this kind of islands is that the last are formed not as a result of a coral reef remained above the surface of the ocean after the subsidence of a volcanic island but as a result of other processes.

While some scientists disagree and seek for another better explanation, according to the most widely accepted definition, pseudo-atolls are all tropical coral island with a ring or partially ring shape, which aren’t formed as a result of the subsidence of an extinct volcanic island.

According to this description, a number of popular islands around the world are actually pseudo-atolls.

Pseudo-atoll by kansasphoto

There are many cases of pseudo-atolls, and probably one of the best known is the tropical paradise of Bermuda.

Scientific researchers show that although the Bermuda Islands are of volcanic origin, what we see above the surface of the ocean is actually not a coral ring remained after the subsidence of an extinct volcano.

In fact, today’s Bermuda Islands are part of the edge of long time ago eroded volcanic crater, part of which is still visible above the ocean surface and is covered with limestone rocks.

In this case, there is no a partially or completely disappeared beneath the ocean surface island, leaving behind only the surrounding reef system.

Actually, what we have in this case is the very edge of the extinct volcano.

Coral Atoll and Lagoon inside
Coral Atoll and Lagoon inside by NASA’s Earth Observatory

Other interesting examples of what we call pseudo-atolls could be given with the archipelago of the Bahamas or even with Florida.

Although there is a number of real atolls too, many of the islands of the Bahamas are actually pseudo-atolls.

The same applies for some of the islands of the Great Barrier Reef, which is the largest on the planet and extends for 2300 km along the eastern coast of Australia.