These two images of the Tuamotu Archipelago, French Polynesia, illustrate diversity in the morphology of atolls, one of the major types of coral reef formations. A typical atoll structure is a lagoon surrounded by a closed rim of cays and shallow spillways that control the exchange of water between the ocean and the lagoon. However, like human beings, this general scheme may vary according to the history of each individual atoll, resulting in a high diversity of morphology, especially for small atolls. The two neighboring atolls shown here have some unique features. What was a lagoon on Nukutavake (19°17′ S 138°48′ W, 6.2 km²) is now dry and completely covered by vegetation. Pinaki (3.54 km²) has a drying shallow lagoon still connected to the ocean via a single narrow spillway. The variation of morphology implies that each atoll may have a different equilibrium between ocean, lagoon, and land ecosystems.
Published Jul 1, 2001
The only atoll in the South Atlantic Ocean is part of Brazil’s Fernando de Noronha archipelago.
Published Feb 29, 2020
This astronaut photograph depicts Apataki Atoll, an atoll in the Tuamotu Islands in the south Pacific. Atolls are ring-like coral islands that nearly or entirely enclose a lagoon. The atoll traces the perimeter of what was once the coastline of a volcanic island. In 1722, Dutch navigator Jakob Roggeveen became the first European to see the Apataki Atoll. It was later visited by Captain Cook in 1774.
Published Mar 6, 2006
Studying corals from above could help scientists understand how these critical ecosystems will weather a changing climate.
Published Jan 31, 2016
Rowley Shoals, a series of atolls off northwestern Australia, are popular with divers and fisherman interested in the hundreds of marine species.
Published Nov 7, 2011
This astronaut photograph shows Mataiva Atoll, the westernmost atoll of the Tuamotu Archipelago.
Published Aug 30, 2010
The ring shape is the result of coral reefs building up around a former volcanic island in the South Pacific.
Published Apr 6, 2009
The Great Barrier Reef is the largest reef system on Earth, with more than 3,000 separate reefs and coral cays. It is also one of the most complex natural ecosystems.
Published May 31, 2016
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