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Photographer's Note

That image was took on a sand stripe, in the midlle of the Indian Ocean. It was a "Baby Atoll".
Long not more than 40 meters and wide around 5 meters.

*Scanned image*

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The word atoll comes from the Dhivehi (Indo-Aryan language of the Maldive Islands) word atholhu (Dhivehi: އަތޮޅު). Its first recorded use in English was in 1625. However, the term was popularised by Charles Darwin who described atolls as a subset in a special class of islands, the unique property of which is the presence of an organic reef.
Atolls are the product of the growth of tropical marine organisms, so these islands are only found in warm tropical waters. Volcanic islands located beyond the warm water temperature requirements of reef building (hermatypic) organisms become seamounts as they subside and are eroded away at the surface. An island that is located where the ocean water temperatures are just sufficiently warm for upward reef growth to keep pace with the rate of subsidence is said to be at the Darwin Point. Islands more polar evolve towards seamounts or guyots; islands more equatorial evolve towards atolls (see Kure Atoll).

Reginald Aldworth Daly offered a somewhat different explanation for atoll formation: islands worn away by erosion (ocean waves and streams) during the last glacial stand of the sea of some 300 feet below present sea level, developed as coral islands (atolls) (or barrier reefs on a platform surrounding a volcanic island not completely worn away) as sea level gradually rose from melting of the glaciers. Discovery of the great depth of the volcanic remnant beneath many atolls (see Midway Atoll), favors the Darwin explanation, although there can be little doubt that fluctuating sea level has had considerable influence on atoll and other reefs.

In terms of total area (lagoon plus reef), the largest atolls are found in the Maldives: Huvadhoo Atoll, having an area of 2800 (or 3200?) km²; the area of Thiladhunmathi and Miladhunmadulu Atolls (two names, but a single atoll structure) is even larger at 3680 km². Another large atoll is Lihou Reef in the Coral Sea, with a lagoon of 2,500 km². However, by far the largest atoll structure of the world is the Great Chagos Bank in the Indian Ocean, a mostly submerged atoll, part of the Chagos Islands, with an area of roughly 13,000 km². If Saya de Malha Bank were to be recognized as a wholly submerged atoll structure, it would be the world's largest, at 40,000 km². Kwajalein in the Marshall Islands, which is sometimes listed as the largest atoll of the world (largest in the Pacific), measures only 846 km², by contrast. Large atolls are also found in the Tuamotu Archipelago, the largest being Rangiroa, with a lagoon area of 1018 km².

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Additional Photos by Paolo Motta (Paolo) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 3781 W: 144 N: 8843] (41222)
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