Atolls are circular reefs with a central lagoon, that have their origin in volcanic islands. The reef was formed on the slopes of the volcano: when it collapses, leave a reef mass surrounding a central lagoon
The circle may be complete or partial, and may have channels connecting the lagoon with the sea, many of them have circular shapes others are irregular.
The atolls are found in tropical waters where temperatures do not drop below 18º, and promote the coral development.
Atolls take millions years to form, the vertical growth of coral is 1mm a year, in the Atlantic Ocean there are very few atolls, because this ocean is youngster compared with the Pacific or Indian oceans.
At first there was a single continent named "Pangea" and when the different continents drifted apart, the waters of the primeval ocean invaded the gap between Europa, America and Africa. That's why in the young Atlantic Ocean has so few atolls.
Video about "Pangea" Produced by Numaga.com
In the Atlantic Ocean atolls are far from large river fresh water, almost all are in the Caribbean where currents are warmer than those of the African coast
See Atlántic atolls in a larger map.
In Mexico Banco Chinchorro is the largest in the northern hemisphere, it has three keys inside and a total area of 800 km² and also near the mexican coast Alacranes with five islets Pérez, Desertora, Pajaros, Chica y Desterrada.
In Brasil atoll das Rocas 265 kms from the brasilian coast and 142 from Fernando de Noronha Is., this atoll has two islets Cemeterio and Farol Key where there is a lighthouse.
Atoll das rocas. (Wikimedia commons)
In Bahamas Hogsty Reef near Inagua Is.
In Colombia near coastal of Nicaragua the atolls, Serrana, Serranilla, Bajo de Alicia completely submerged, Petrel Is., Quitasueño, Roncador, Courtown y Albuquerque.
In Bermuda islands, the coral is formed despite its latitude due to the warm Gulf stream, but its structure is not the same of the tropical atolls.
In Bermuda islands, the coral is formed despite its latitude due to the warm Gulf stream, but its structure is not the same of the tropical atolls.
