What is an atoll?

Have you ever been on vacation and visited a beautiful lagoon beach that had dark spots in the middle?

Well, this is an atoll and here we explain everything about the coral reef phenomenon.

An atoll is surrounded by a coral reef barrier


An atoll is surrounded by a coral reef barrierCredit: Alamy

What is an atoll?

An atoll is described as a ring-shaped coral reef, or an island, or a series of islets.

It surrounds a body of water called the Lagoon, which is a shallow body of water separate from the larger body of water.

Sites containing atolls have proven dangerous throughout history.

They are obscured by sea waves and because of them there were wrecks of old Polynesian canoes and American warships.

Kon-Tiki is one of history’s most famous shipwrecks, caused by the strong winds and currents that encircle an atoll.

It was built and sailed by explorer Thor HeyerDahl and his crew in 1947.

It sailed a distance of 6,980 km from Peru to the South Pacific before encountering difficulties in the Polynesia region just as they were about to reach the first island.

The atoll prevented the Kon-Tiki from docking with the island and crashed into the coral of the second Raroia atoll.

Nearby islanders came to the aid of the Europeans on board and rescued them from the washed up wreck.

For this reason most of the atolls are inhabited islands as they are very difficult to reach.

One can find many shipwrecks from the 18th century to WWII at the foot of the atoll sites.

Because they are deserted islands, they have been a favorite spot for the United States, Britain, and France to test nuclear weapons.

How are atolls formed?

The process begins when an underwater volcano, also called seamounts, erupts and piles lava on the sea floor.

Eventually, it breaks out of the water table and becomes an oceanic island.

Then corals start to build a reef around the island and it becomes what is called a fringing reef.

It surrounds the island below the sea surface, making the water between the reef and the island a lagoon.

It takes millions of years for the allotment to fully form.

A process called subsidence takes place in which the volcanic island erodes and subsides.

The sea waves flatten the top, turning it into what is known as a guyot.

The fringing reef turns into a barrier reef that protects the lagoon from strong winds and waves.

Eventually, the sea waves begin to break part of the reef, creating tiny grains of sand and other material.

This includes organic matter such as plant seeds forming a ring-shaped island, forming an atoll.

Where are atolls in the world?

There are several atolls to be found around the world and despite their dangers they can be a sight of sheer beauty.

Atolls of the Maldives

The Maldives has 1,200 atolls and offers visitors the opportunity to engage in some water sport activities.

The scenic beauty of these atolls offers a great snorkeling and diving experience.

Bikini Atoll

Remember when we said that some countries used atolls to test nuclear weapons in?

Well, Bikini Atoll was one of those atolls that is located in the Marshall Islands.

The US used it to test 23 nuclear devices at seven different locations in the atoll between 1946 and 1958.

Now it is used as a tourist attraction to dive and take a look at the shipwrecks that have accumulated over the years.

Caroline Island

Caroline Island is one of the cleanest and most pristine tropical islands in the world with one of the largest populations of coconut crabs.

It is considered a nature reserve because of its low level of pollution.

However, you may not have long to visit such an island as it is expected to be fully submerged by 2025 as it is six meters above sea level.

Lighthouse Reef

It is one of the four atolls in the Western Hemisphere and is famous for the Great Blue Hole at its centre.

It is considered one of the best places for diving because the deeper you go, the more you can discover thanks to the clear waters below.

There are stalactites and limestone formations that offer the diver views of exceptional beauty.


It lies between Hawaii and Australia in the capital Tuvalu.

It is only 20 meters wide on the narrowest sides and reaches 400 meters on the widest sides.

With 6,200 inhabitants, it is the second most sparsely populated country in the world after Vatican City and offers many activities centered around its marine life.

https://www.the-sun.com/news/5450460/what-is-an-atoll/ What is an atoll?


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