What is an Atoll?

An atoll is an island that is constructed of coral and encircles a lagoon. Found most often in tropical sections of the Pacific and Indian oceans, atolls are noted for creating an attractive and peaceful setting.

During the middle of the 19th century, Charles Darwin developed was the developer of the more commonly accepted theory of how an atoll is formed. He understood the creation process as having its roots in volcanic activity. The basis for his theory came from personal observations that Darwin made during a six-year voyage around the southern section of the Pacific Ocean.

According to Darwin, the atoll was the result of the gradual sinking of a volcanic island that has long since cooled, leaving behind an open crater in the middle section of the island. As the island begins to sink, the surrounding territory of the island falls beneath the surface of the water. At the same time, the coral reef that is found around the fringes of the island remains and gradually is built up through the natural practice of the accumulation of marine organisms that become part of the reef. This creates a barrier reef around the remaining section of the island, forming the perfect conditions for the development of a lagoon. Once the lagoon is formed and is more or less encircled by the barrier reef, an atoll is the final product of this gradual metamorphosis.

Most of the examples of these structures are found in warm waters. The reason for this is that the tropical climate is necessary to help build up the barrier reefs and create the lagoons that connect the islands and the reef formations. When conditions of weather and reef formation are understood to be minimally suitable for the formation of an atoll, they are said to be at the Darwin Point.

Many of the world’s most popular atolls are found in the Pacific Ocean, especially around the Caroline and Marshall Islands. The Indian Ocean is also home to many, such as the Atolls of the Maldives. Very few atolls are found in the Atlantic Ocean, although there is a series of eight found just off the eastern coast of Nicaragua.

An atoll is a ring-shaped coral reef, island, or series of islets that encircle a lagoon, either partially or completely. They are usually found in warm ocean waters and are formed from the growth of coral reefs around a volcanic island that has since subsided below sea level, leaving the ring of coral exposed.

Atolls are formed through a process that begins with a volcanic island which becomes surrounded by a coral reef. Over time, the island erodes and sinks due to subsidence and sea level changes, while the coral continues to grow upwards. Eventually, the original island disappears beneath the water, leaving a lagoon surrounded by the coral reef.

Atolls are commonly found in the warm, tropical waters of the Pacific and Indian Oceans. The Maldives, for example, is a nation composed entirely of atolls and is the lowest-lying country on Earth. The largest atoll in the world by land area is Kiritimati (Christmas Island) in the Pacific Ocean.

Atolls boast a rich biodiversity, including various species of coral, fish, mollusks, birds, and marine mammals. They serve as important habitats for marine life, offering food and shelter. The coral reefs are particularly crucial as they host an estimated 25% of all marine species, despite covering less than 1% of the ocean floor.

Yes, atolls are at significant risk due to climate change. Rising sea levels can lead to increased flooding and erosion, while warmer ocean temperatures can cause coral bleaching, which damages the reef ecosystem. Atolls' low elevation makes them particularly vulnerable to the effects of climate change.

People do live on atolls, and they often sustain their communities through fishing, tourism, and the cultivation of crops like coconuts. However, living on atolls can be challenging due to limited freshwater resources, vulnerability to storms, and the impacts of climate change, which threaten their livelihoods and homes.