A white sandy beach surrounds a quiet lagoon, lush palm trees slope towards turquoise water, in which bright fish scurry - this is an atoll, an island on a coral reef. Atolls are located in the Pacific and Indian Oceans at tropical latitudes and attract tourists and divers from all over the world.
The origin of the atolls
It takes a long time for a new atoll to emerge. At the top of an extinct volcano, a coral reef forms under water. Increasing more and more new floors, corals gradually come to the surface. Soil is applied to the corals, and an island is formed in the form of a vent of a long-cooled volcano.
If the water level drops or the base of the reef rises as a result of the movement of tectonic plates, the atoll protrudes from the ocean in the form of a whole ring. A closed lake, called a lagoon, will then be less salty than the water around the atoll. It often happens that the reef protrudes from the water in the form of several islets, the highest parts of it, which are separated by straits. Also, one strait can open the ring of the atoll.
Usually the atoll rises above sea level by 3-4 meters. If the water level drops, an uplifted atoll forms. If an atoll goes under water, it is called a submerged, or underwater bank, a shallow. These insidious shoals have destroyed many sailing ships in the era of great geographical discoveries.
The size of the islands and the depth of the lagoons
The largest atolls are located in the Marshall Islands archipelago. One of the largest atoll on earth, Kwajalen atoll consists of 92 islets, the total area of which is 14.5 km². However, the lagoon of this atoll stretches for 300 kilometers and occupies 92% of the total area of this atoll.
The largest atoll in the world is Christmas Island in the Line archipelago with a land area of 321 km².
Rangiroa, the largest atoll in the Tuamotu archipelago, covers 1,639 km², with 241 islets accounting for 43 km². Such atolls are formed not on one volcano, but on a whole volcanic plateau. The deep Rangiroa lagoon is rich in marine life, and sharks and dolphins can be seen among the usual colorful inhabitants of the coral reefs.
The depth of the lagoons inside the atolls usually ranges from 15 to 30 meters, but there are lagoons up to 90 meters deep.
The most famous atolls
Bikini Atoll, part of the Marshall Islands, was the Pacific proving ground for American nuclear tests after World War II. Twenty-three atomic bombs of varying power went off in Bikini Atoll. The result was severe radioactive contamination, which the Americans could not neutralize and were forced to stop testing.
Bikini Atoll gave its name to the famous swimsuit, which was invented shortly after the first explosion. It was assumed that the swimsuit gives the impression of an exploding bomb.
The sad glory of Bikini Atoll is a thing of the past. Today, the most famous are the 26 atolls, which are home to the tiny Republic of Maldives in the Indian Ocean. The wonderful transparency of the water here allows you to study not only the underwater inhabitants, but also explore the sunken ships, and the fabulous beauty of the 1190 Maldives conquers the hearts of seekers of untouched corners of the Earth.
