View source for Atoll

{{Short description|Ring-shaped coral reef}}
{{Redirect|Atolls|the company|Atolls (company)|other uses|Atoll (disambiguation)}}
[[File:Tetiaroa from sky.JPG|thumb|The atoll of [[Tetiʻaroa]] in [[French Polynesia]]]]

An '''atoll''' ({{IPAc-en|ˈ|æ|t|.|ɒ|l|,_|-|ɔː|l|,_|-|oʊ|l|,_|ə|ˈ|t|ɒ|l|,_|-|ˈ|t|ɔː|l|,_|-|ˈ|t|oʊ|l}})<ref>{{cite Dictionary.com|atoll}}</ref> is a ring-shaped island, including a [[coral]] rim that encircles a [[lagoon]]. There may be [[coral island]]s or [[cay]]s on the rim.<ref name="Migon2010">{{cite book |editor-first=Piotr |editor-last=Migoń|editor-link=Piotr Migoń|title=Geomorphological Landscapes of the World|url=https://books.google.com/books?id=-TI55urJYyEC|access-date=12 February 2013 |year=2010 |publisher=Springer |isbn=978-90-481-3055-9 |page=349}}</ref><ref name="blakegh1" /> Atolls are located in warm [[Tropics|tropical]] or [[Subtropics|subtropical]] parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the [[Pacific Ocean]].

Two different, well-cited models, the subsidence model and the antecedent [[karst]] model, have been used to explain the development of atolls.<ref name="DroxlerOthers2021a">Droxler, A.W. and Jorry, S.J., 2021. "The Origin of Modern Atolls: Challenging Darwin's Deeply Ingrained Theory". ''Annual Review of Marine Science'', 13, pp. 537–573.</ref> According to [[Charles Darwin]]'s subsidence model,<ref name="darwincr1" /> the formation of an atoll is explained by the sinking of a [[volcanic island]] around which a coral fringing reef has formed. Over geologic time, the volcanic island becomes extinct and eroded as it subsides completely beneath the surface of the ocean. As the volcanic island subsides, the coral fringing reef becomes a [[barrier reef]] that is detached from the island. Eventually, the reef and the small coral islets on top of it are all that is left of the original island, and a lagoon has taken the place of the former volcano. The lagoon is not the former volcanic crater. For the atoll to persist, the coral reef must be maintained at the sea surface, with coral growth matching any relative change in sea level (sinking of the island or rising oceans).<ref name="DroxlerOthers2021a"/>

An alternative model for the origin of atolls is called the antecedent karst model. In the antecedent karst model, the first step in the formation of an atoll is the development of a flat top, mound-like coral reef during the subsidence of an oceanic island of either volcanic or nonvolcanic origin below sea level. Then, when relative sea level drops below the level of the flat surface of coral reef, it is exposed to the atmosphere as a flat topped island which is dissolved by rainfall to form limestone [[karst]]. Because of hydrologic properties of this karst, the rate of dissolution of the exposed coral is lowest along its rim and the rate of dissolution increases inward to its maximum at the center of the island. As a result, a saucer shaped island with a raised rim forms. When relative sea level submerges the island again, the rim provides a rocky core on which coral grow again to form the islands of an atoll and the flooded bottom of the saucer forms the lagoon within them.<ref name="DroxlerOthers2021a"/><ref name="Purdy1974a">Purdy, E. G., 1974. "Reef configurations, cause and effect". In Laporte, L. F. (ed.), ''Reefs in Time and Space''. ''Society of Economic Palaeontologists and Mineralogists Special Publication'' 18, pp. 9–76.</ref>

== Usage ==
The word ''atoll'' comes from the [[Maldivian language|Dhivehi]] word {{Transliteration|dv|atholhu}} ({{lang|dv|އަތޮޅު}}, {{IPA|dv|ˈat̪oɭu|pron}}). Dhivehi is an [[Indo-Aryan languages|Indo-Aryan language]] spoken in the [[Maldives]]. The word's first recorded English use was in 1625 as ''atollon''. [[Charles Darwin]] coined the term in his monograph, ''[[The Structure and Distribution of Coral Reefs]]''. He recognized the word's indigenous origin and defined it as a "circular group of coral islets", synonymously with "lagoon-island".<ref name="darwincr1" />{{rp|page=2}}

More modern definitions of ''atoll'' describe them as "annular reefs enclosing a lagoon in which there are no [[promontory|promontories]] other than reefs and [[islet]]s composed of reef [[detritus]]"<ref>McNeil (1954, p. 396).</ref> or "in an exclusively morphological sense, [as] a ring-shaped ribbon reef enclosing a lagoon".<ref>Fairbridge (1950, p. 341).</ref>

== Distribution and size ==
There are approximately 440 atolls in the world.<ref name="Watts2019">{{cite journal|title=Science, Seamounts and Society |author=Watts, T. |journal=Geoscientist |year=2019 |volume=August 2019 |pages=10–16}}</ref> Most of the world's atolls are in the Pacific Ocean (with concentrations in the [[Caroline Islands]], the [[Coral Sea Islands]], the [[Marshall Islands]], the [[Tuamotu Islands]], [[Kiribati]], [[Tokelau]], and [[Tuvalu]]) and the [[Indian Ocean]] (the [[Chagos Archipelago]], [[Lakshadweep]], the [[atolls of the Maldives]], and the [[Outer Islands (Seychelles)|Outer Islands]] of [[Seychelles]]). In addition, Indonesia also has several atolls spread across the archipelago, such as in the [[Thousand Islands (Indonesia)|Thousand Islands]], [[Taka Bonerate Islands]], and atolls in the [[Raja Ampat Islands]]. The Atlantic Ocean has no large groups of atolls, other than eight atolls east of [[Nicaragua]] that belong to the [[Colombia]]n department of [[Archipelago of San Andrés, Providencia and Santa Catalina|San Andres and Providencia]] in the Caribbean.

Reef-building corals will thrive only in warm [[tropics|tropical]] and [[subtropics|subtropical]] waters of oceans and seas, and therefore atolls are found only in the tropics and subtropics. The northernmost atoll in the world is [[Kure Atoll]] at 28°25′ N, along with other atolls of the [[Northwestern Hawaiian Islands]]. The southernmost atolls in the world are [[Elizabeth Reef]] at 29°57′ S, and nearby [[Middleton Reef]] at 29°27′ S, in the [[Tasman Sea]], both of which are part of the [[Coral Sea Islands]] Territory. The next southerly atoll is [[Ducie Island]] in the [[Pitcairn Islands]] Group, at 24°41′ S. 
The atoll closest to the Equator is [[Aranuka]] of Kiribati. Its southern tip is just {{cvt|13|km|sigfig=1}} north of the Equator.

[[Bermuda]] is sometimes claimed as the "northernmost atoll" at a [[latitude]] of 32°18′ N. At this latitude, coral reefs would not develop without the warming waters of the [[Gulf Stream]]. However, Bermuda is termed a ''[[pseudo-atoll]]'' because its general form, while resembling that of an atoll, has a very different origin of formation.

In most cases, the land area of an atoll is very small in comparison to the total area. Atoll islands are low lying, with their elevations less than {{convert|5|m|ft}}. Measured by total area, [[Lifou]] ({{cvt|1146|km2|disp=comma}}) is the largest [[raised coral atoll]] of the world, followed by [[Rennell Island]] ({{cvt|660|km2|disp=comma}}).<ref>{{cite web |url=http://www.worldislandinfo.com/MISINFORMATION.htm |title=Misinformation about Islands |publisher=worldislandinfo.com}}</ref> More sources, however, list [[Kiritimati]] as the largest atoll in the world in terms of land area. It is also a raised coral atoll ({{cvt|321|km2|disp=comma}} land area; according to other sources even {{cvt|575|km2|disp=comma}}), {{cvt|160|km2}} main lagoon, {{cvt|168|km2}} other lagoons (according to other sources {{cvt|319|km2|disp=comma}} total lagoon size).

The geological formation known as a [[reef knoll]] refers to the elevated remains of an ancient atoll within a limestone region, appearing as a hill. The second largest atoll by dry land area is [[Aldabra]], with {{cvt|155|km2}}. [[Huvadhu Atoll]], situated in the southern region of the Maldives, holds the distinction of being the largest atoll based on the sheer number of islands it comprises, with a total of 255 individual islands.

[[File:On the structure and distribution of coral reefs BHL40453231.jpg|thumb|upright=3|center|Map from [[Charles Darwin]]'s 1842 ''[[The Structure and Distribution of Coral Reefs]]'' showing the world's major groups of atolls and coral reefs]]

===List of atolls===
{| class="wikitable plainrowheaders sortable static-row-numbers sort-under col1right"
|+ style="padding-bottom: 0.5em" | Largest atolls by total area (lagoon plus reef and dry land)<ref>{{Cite FTP |url = ftp://rock.geosociety.org/pub/reposit/2001/2001075.pdf |title = Atoll Area, Depth and Rainfall|date = 2001|server = The Geological Society of America |url-status = dead |format= spreadsheet }}</ref>
|-
! scope="col" | Name
! scope="col" | Position
! scope="col" | Location
! scope="col" style="max-width: 4em;" | Land area (km<sup>2</sup>)
! scope="col" style="max-width: 4em;" | Total area (km<sup>2</sup>)
! scope="col" | Notes
|-
! scope="row" | [[Great Chagos Bank]]
| {{Coord|-6.17|72.00|display=inline}}
| [[Indian Ocean]]
| style="text-align: right;" | 4.5
| style="text-align: right;" | 12,642
| 
|-
! scope="row" | Reed Bank
| {{Coord|11.45|116.90|display=inline}}
| [[Spratly Islands]]
| style="text-align: right;" |
| style="text-align: right;" | 8,866
| Submerged, at shallowest 9 m
|-
! scope="row" | [[Macclesfield Bank]]
| {{Coord|16.00|114.50|display=inline}}
| [[South China Sea]]
| style="text-align: right;" |
| style="text-align: right;" | 6,448
| Submerged, at shallowest 9.2 m
|-
! scope="row" | North Bank
| {{Coord|-9.07|60.20|display=inline}}
| North of [[Saya de Malha Bank]]
| style="text-align: right;" |
| style="text-align: right;" | 5,800
| Submerged, at shallowest <10 m
|-
! scope="row" | [[Rosalind Bank]]
| {{Coord|16.43|-80.52|display=inline}}
| [[Caribbean]]
| style="text-align: right;" |
| style="text-align: right;" | 4,500
| Submerged, at shallowest 7.3 m
|-
! scope="row" | [[Thiladhunmathi]]
| {{Coord|6.73|73.04|display=inline}}
| [[Maldives]]
| style="text-align: right;" | 51
| style="text-align: right;" | 3,850
| 
|-
! scope="row" | [[Chesterfield Islands]]
| {{Coord|-19.35|158.66|display=inline}}
| [[New Caledonia]]
| style="text-align: right;" | <10
| style="text-align: right;" | 3,500
| 
|-
! scope="row" | [[Huvadhu Atoll]]
| {{Coord|0.50|73.30|display=inline}}
| [[Maldives]]
| style="text-align: right;" | 38.5
| style="text-align: right;" | 3,152
| 
|-
! scope="row" | [[Chuuk Lagoon]]
| {{Coord|7.42|151.78|display=inline}}
| [[Chuuk State|Chuuk]], Micronesia
| style="text-align: right;" | 
| style="text-align: right;" | 3,152
| 
|-
! scope="row" | [[Sabalana Islands]]
| {{Coord|-6.75|118.83|display=inline}}
| [[Indonesia]]
| style="text-align: right;" | 
| style="text-align: right;" | 2,694
|
|-
! scope="row" | [[Lihou Reef National Nature Reserve|Lihou Reef]]
| {{Coord|-17.42|151.67|display=inline}}
| [[Coral Sea]]
| style="text-align: right;" | 1
| style="text-align: right;" | 2,529
| 
|-
! scope="row" | [[Bassas de Pedro]]
| {{Coord|13.08|72.42|display=inline}}
| [[Lakshadweep]], [[India]]
| style="text-align: right;" |
| style="text-align: right;" | 2,474
| Submerged, at shallowest 16.4 m
|-
! scope="row" | Ardasier Bank
| {{Coord|7.71|114.25|display=inline}}
| [[Spratly Islands]]
| style="text-align: right;" |
| style="text-align: right;" | 2,347
| 
|-
! scope="row" | [[Kwajalein Atoll]]
| {{Coord|9.19|167.47|display=inline}}
| [[Marshall Islands]]
| style="text-align: right;" | 16.4
| style="text-align: right;" | 2,304
| 
|-
! scope="row" | Diamond Islets Bank
| {{Coord|-17.42|150.96|display=inline}}
| [[Coral Sea]]
| style="text-align: right;" | <1
| style="text-align: right;" | 2,282
| 
|-
! scope="row" | [[Namonuito Atoll]]
| {{Coord|8.67|150.00|display=inline}}
| [[Chuuk State|Chuuk]], Micronesia
| style="text-align: right;" | 4.4
| style="text-align: right;" | 2,267
| 
|-
! scope="row" | [[Ari Atoll]]
| {{Coord|3.86|72.83|display=inline}}
| [[Maldives]]
| style="text-align: right;" | 69
| style="text-align: right;" | 2,252
| 
|-
! scope="row" | [[Maro Reef]]
| {{Coord|25.42|-170.59|display=inline}}
| [[Northwestern Hawaiian Islands]]
| style="text-align: right;" |
| style="text-align: right;" | 1,934
|
|-
! scope="row" | [[Rangiroa]]
| {{Coord|-15.13|-147.65|display=inline}}
| [[Tuamotus]]
| style="text-align: right;" | 79
| style="text-align: right;" | 1,762
| 
|-
! scope="row" | [[Kolhumadulu Atoll]]
| {{Coord|2.37|73.12|display=inline}}
| [[Maldives]]
| style="text-align: right;" | 79
| style="text-align: right;" | 1,617
| 
|-
! scope="row" | [[Kaafu Atoll]]
| {{Coord|4.42|73.50|display=inline}}
| [[Maldives]]
| style="text-align: right;" | 69
| style="text-align: right;" | 1,565
| 
|-
! scope="row" | [[Ontong Java Atoll]]
| {{Coord|-5.27|159.35|display=inline}}
| [[Solomon Islands]]
| style="text-align: right;" | 12
| style="text-align: right;" | 1500
| 
|-
! scope="row" | [[Lifou Island|Lifou]]
| {{Coord|-20.97|167.23|display=inline}}
| [[New Caledonia]]
| style="text-align: right;" | 
| style="text-align: right;" | 1146
| Raised atoll with no lagoon
|-
! scope="row" | [[Rennell Island|Rennell]]
| {{Coord|-11.67|160.17|display=inline}}
| [[Solomon Islands]]
| style="text-align: right;" |
| style="text-align: right;" | 660
| Raised atoll with no lagoon
|-
! scope="row" | [[Kiritimati]]
| {{Coord|1.85|-157.4|display=inline}}
| [[Kiribati]]
| style="text-align: right;" | 312
| style="text-align: right;" | 640
| 
|}

===Gallery===
<gallery widths="200" heights="200">
Penrhyn Aerial EFS 1280.jpg|[[Penrhyn (atoll)|Penrhyn]] atoll
Maldives.visibleearth.nasa.jpg|upright|[[NASA]] satellite image of some of the [[atolls of the Maldives]], which consists of 1,322 islands arranged into 26 atolls
Nukuoro ISS013-E-28610.jpg|[[Nukuoro]] from space. Courtesy [[NASA]]
Los Roques.png|[[Los Roques Archipelago]] in Venezuela, the largest marine national park in Latin America,<ref name="inparques1" /> from space. Courtesy [[NASA]]
Bikini Atoll Nuclear Test Site-115017.jpg|View of the coast of [[Bikini Atoll]] from above
Maamigili Island Raa Atoll.jpg|[[Raa Atoll]] in [[Maldives]]
Guriadhoo-2019-aerial-view-Luka-Peternel.jpg|[[Kaafu Atoll]] in [[Maldives]]
</gallery>

== Formation<span class="anchor" id="Darwin Point"></span> ==
{{See also|Coral reef#Formation}}
[[File:Bora Bora (16542797633).jpg|thumb|Aerial view of [[Bora Bora]], French Polynesia]]
[[File:South Tarawa from the air.jpg|thumb|[[Tarawa Atoll]], Republic of Kiribati]]
[[File:Bikini Atoll.png|thumb|[[Bikini Atoll]], Marshall Islands]]

In 1842, Charles Darwin<ref name="darwincr1" /> explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a five-year voyage aboard HMS Beagle from 1831 to 1836. Darwin's explanation suggests that several tropical island types: from high volcanic island, through barrier reef island, to atoll, represented a sequence of gradual subsidence of what started as an oceanic volcano. He reasoned that a fringing coral reef surrounding a volcanic island in the tropical sea will grow upward as the island subsides (sinks), becoming an "almost atoll", or barrier reef island, as typified by an island such as Aitutaki in the Cook Islands, and Bora Bora and others in the Society Islands. The fringing reef becomes a barrier reef for the reason that the outer part of the reef maintains itself near sea level through biotic growth, while the inner part of the reef falls behind, becoming a lagoon because conditions are less favorable for the coral and calcareous algae responsible for most reef growth. In time, subsidence carries the old volcano below the ocean surface and the barrier reef remains. At this point, the island has become an atoll.

As formulated by J. E. Hoffmeister,<ref name="Hoffmeister1930a">Hoffmeister, J.E., 1930. "Erosion of elevated fringing coral reefs". ''Geological Magazine'', 67(12), pp. 549–554.</ref> F. S. McNeil,<ref name="MacNeil1954a">MacNeil, F.S., 1954. [https://ajsonline.org/article/58503 "The Shape of Atolls; an Inheritance from Subaerial Erosion Forms"]. ''American Journal of Science'', 252(7), pp. 402–427. {{doi|10.2475/ajs.252.7.402}}.</ref> E. G. Prudy,<ref name="Purdy1974a"/> and others, the antecedent karst model argues that atolls are [[Pleistocene]] features that are the direct result of the interaction between subsidence and preferential karst dissolution that occurred in the interior of flat topped coral reefs during exposure during glacial lowstands of sea level. The elevated rims along an island created by this preferential karst dissolution become the sites of coral growth and islands of atolls when flooded during interglacial highstands.

The research of A. W. Droxler, Stéphan J Jorry and others<ref name="DroxlerOthers2021a"/> supports the antecedent karst model as they found that the morphology of modern atolls are independent of any influence of an underlying submerged and buried island and are not rooted to an initial fringing reef/barrier reef attached to a slowly subsiding volcanic edifice. In fact, the Neogene reefs underlying the studied modern atolls overlie and completely bury the subsided island are all non-atoll, flat-topped reefs. In fact, they found that atolls did not form doing the subsidence of an island until MIS-11, Mid-Brunhes, long after the many the former islands had been completely submerged and buried by flat topped reefs during the Neogene.

Atolls are the product of the growth of tropical marine organisms, and so these islands are found only in warm tropical waters. Volcanic islands located beyond the warm water temperature requirements of [[hermatypic]] (reef-building) organisms become [[seamount]]s 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 in colder, more polar regions evolve toward seamounts or [[guyot]]s; warmer, more equatorial islands evolve toward atolls, for example [[Kure Atoll]]. However, ancient atolls during the [[Mesozoic]] appear to exhibit different growth and evolution patterns.<ref>{{cite journal |last1=Bialik |first1=Or M. |last2=Samankassou |first2=Elias |last3=Meilijson |first3=Aaron |last4=Waldmann |first4=Nicolas D. |last5=Steinberg |first5=Josh |last6=Karcz |first6=Kul |last7=Makovsky |first7=Yizhaq |title=Short-lived early Cenomanian volcanic atolls of Mt. Carmel, northern Israel |journal=Sedimentary Geology |date=January 2021 |volume=411 |article-number=105805 |doi=10.1016/j.sedgeo.2020.105805|bibcode=2021SedG..41105805B |s2cid=228873675 }}</ref><ref>{{cite journal |last1=El-Yamani |first1=Mahmoud S. |last2=John |first2=Cédric M. |last3=Bell |first3=Rebecca |title=Stratigraphic evolution and karstification of a Cretaceous Mid-Pacific atoll (Resolution Guyot) resolved from core-log-seismic integration and comparison with modern and ancient analogues |journal=Basin Research |date=16 May 2022 |volume=34 |issue=5 |pages=1536–1566 |doi=10.1111/bre.12670|bibcode=2022BasR...34.1536E |hdl=10044/1/98098 |s2cid=248223664 |hdl-access=free }}</ref>

<gallery widths="200" heights="160">
Atoll forming-volcano.png|Darwin's theory starts with a [[volcanic island]] which becomes extinct
Atoll forming-Fringing reef.png|As the island and ocean floor subside, coral growth builds a [[fringing reef]], often including a shallow lagoon between the land and the main reef
Atoll forming-Barrier reef.png|As the subsidence continues the fringing reef becomes a larger barrier reef farther from the shore with a bigger and deeper [[lagoon]] inside
Atoll forming-Atoll.png|Ultimately the island sinks below the sea, and the barrier reef becomes an atoll enclosing an open lagoon
</gallery>

Coral atolls are important as sites where [[dolomitization]] of calcite occurs. Several models have been proposed for the dolomitization of [[calcite]] and [[aragonite]] within them. They are the evaporative, seepage-reflux, mixing-zone, burial, and seawater models. Although the origin of replacement [[Dolomite (rock)|dolomites]] remains problematic and controversial, it is generally accepted that seawater was the source of magnesium for dolomitization and the fluid in which calcite was dolomitized to form the dolomites found within atolls. Various processes have been invoked to drive large amounts of seawater through an atoll in order for dolomitization to occur.<ref name="Budd1997a">Budd, D.A. (March 1997). [https://www.sciencedirect.com/science/article/abs/pii/S0012825296000517 "Cenozoic dolomites of carbonate islands: their attributes and origin"] {{subscription required}}. ''Earth-Science Reviews'', 42(1–2), pp. 1–47. {{doi|10.1016/S0012-8252(96)00051-7}}.</ref><ref name="WheelerOthers1999a">Wheeler, C.W., Aharon, P. and Ferrell, R.E. (1 January 1999). [https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/69/1/239/99004/Successions-of-late-Cenozoic-platform-dolomites "Successions of late Cenozoic platform dolomites distinguished by texture, geochemistry, and crystal chemistry; Niue, South Pacific"]. ''Journal of Sedimentary Research'', 69(1), pp. 239–255. {{doi|10.2110/jsr.69.239}}.</ref><ref name="SuzkiOthers2006a">Suzuki, Y., Iryu, Y., Inagaki, S., Yamada, T., Aizawa, S. and Budd, D.A. (15 January 2006). [https://www.sciencedirect.com/science/article/abs/pii/S0037073805003167 "Origin of Atoll Dolomites Distinguished by Geochemistry and Crystal Chemistry: Kita-Daito-Jima, Northern Philippine Sea"]. ''Sedimentary Geology'', 183(3–4), pp. 181–202. {{doi|10.1016/j.sedgeo.2005.09.016}}.</ref>

== Investigation by the Royal Society of London==
[[File:Wake Island air.JPG|thumb|Aerial overview of the [[Wake Island]] atoll, part of the [[Pacific Islands Heritage Marine National Monument]]]]

In 1896, 1897 and 1898, the [[Royal Society of London]] carried out drilling on [[Funafuti]] atoll in [[Tuvalu]] for the purpose of investigating the [[formation of coral reefs]]. They wanted to determine whether traces of shallow water organisms could be found at depth in the [[coral]] of Pacific atolls. This investigation followed the work on [[The Structure and Distribution of Coral Reefs|the structure and distribution of coral reefs]] conducted by [[Charles Darwin]] in the Pacific.

The first expedition in 1896 was led by Professor [[William Johnson Sollas]] of the [[University of Oxford]]. Geologists included [[Walter George Woolnough]] and [[Edgeworth David]] of the [[University of Sydney]]. Professor Edgeworth David led the expedition in 1897.<ref name="davidcm1" /> The third expedition in 1898 was led by Alfred Edmund Finckh.<ref name="finckhae1" /><ref name="cantrellc1" /><ref name="rodgerska1" />

== See also ==
{{Portal|Islands}}
{{Clear|left}}
* [[Baratal limestone]], sometimes described as the oldest known atoll
* [[Coral island]]

== References ==
===Inline citations===
{{Reflist|refs=
<ref name="blakegh1">{{cite book
| editor-first = Gerald Henry
| editor-last  = Blake
| volume       = 5 Maritime Boundaries
| title        = World Boundary Series
| url          = https://books.google.com/books?id=Vpdl5O3myGEC
| access-date   = 12 February 2013
| year         = 1994
| publisher    = [[Routledge]]
| isbn         = 978-0-415-08835-0
| ref          = blakegh-1
}}</ref>
<ref name="darwincr1">{{cite book
| title         = The structure and distribution of coral reefs. Being the first part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836
| url           = http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F271&pageseq=1
| via           = Darwin Online
| first         = Charles R
| last          = Darwin
| author-link    = Charles Darwin
| location      = London
| publisher     = [[Smith, Elder & Co.|Smith Elder and Co]]
| year          = 1842
| ref           = darwincr-1
}}</ref>
<ref name="inparques1">{{cite web
 |url=http://www.inparques.gob.ve/index.php?parques=view&codigo=pn_0009&sec=2 
 |title=Archipiélago de Los Roques 
 |year=2007 
 |publisher=Instituto Nacional de Parques (INPARQUES) 
 |location=Caracas, Venezuela 
 |language=es 
 |access-date=27 February 2013 
 |ref=inparques-1 
 |archive-url=https://web.archive.org/web/20080424204206/http://www.inparques.gob.ve/index.php?parques=view&codigo=pn_0009&sec=2 
 |archive-date=2008-04-24 
}}</ref>
<ref name="davidcm1">{{cite book
| title        = Funafuti or Three Months on a Coral Atoll: An Unscientific Account of a Scientific Expedition
| last1        = David
| first1       = Cara (Caroline Martha)
| location     = London
| publisher    = [[John Murray (publishing house)|John Murray]]
| year         = 1899
| isbn         = 978-1-151-25616-4
| ref          = davidcm-1
}}</ref>
<ref name="finckhae1">{{cite news
| first         = Dr. Alfred Edmund
| last          = Finckh
| title         = To the Editor of the Herald.
| url           = http://nla.gov.au/nla.news-article17092086
| newspaper     = [[The Sydney Morning Herald]]
| location      = NSW
| date          = 11 September 1934
| access-date    = 20 June 2012
| page          = 6
| publisher     = National Library of Australia
| ref           = finckhae-1
}}</ref>
<ref name="cantrellc1">{{cite book
| first         = Carol
| last          = Cantrell
| year          = 1996
| chapter       = Alfred Edmund Finckh (1866–1961)
| chapter-url   = https://adb.anu.edu.au/biography/finckh-alfred-edmund-10180/text17987
| title         = Australian Dictionary of Biography
| title-link    = Australian Dictionary of Biography
| publisher     = National Centre of Biography, [[Australian National University]]
| access-date   = 23 December 2012
| ref           = cantrellc-1
}}</ref>
<ref name="rodgerska1">{{cite journal
| first1       = K A
| last1        = Rodgers
| first2       = Carol
| last2        = Cantrell
| title        = Alfred Edmund Finckh 1866–1961: Leader of the 1898 Coral Reef Boring Expedition to Funafuti
| journal      = Historical Records of Australian Science
| volume       = 7
| issue        = 4
| pages        = 393–403
| doi          = 10.1071/HR9890740393
| pmid         = 11617111
| ref          = rodgerska-1
| year = 1987
}}</ref>
<!-- <ref name="bush8336">{{cite web
| url           = http://www.fws.gov/pacificremoteislandsmarinemonument/PP%20PRIMNM.pdf
| title         = Presidential Proclamation 8336
| date          = 6 January 2009
| publisher     = The White House
| ref           = bush-8336
}}</ref>
<ref name="usweekly1">{{cite web
 |url=http://fdsys.gpo.gov/fdsys/pkg/WCPD-2009-01-12/pdf/WCPD-2009-01-12.pdf 
 |title=Weekly Compilation of Presidential Documents 
 |date=12 January 2009 
 |volume=45 
 |ref=usweekly-1 
 |archive-url=https://web.archive.org/web/20090301125355/http://fdsys.gpo.gov/fdsys/pkg/WCPD-2009-01-12/pdf/WCPD-2009-01-12.pdf 
 |archive-date=March 1, 2009 
}}</ref> -->
}}

===Sources===
* Dobbs, David (2005). ''Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral''.  Pantheon. {{ISBN|0-375-42161-0}}.
* Fairbridge, R. W. (July 1950). [https://www.journals.uchicago.edu/doi/abs/10.1086/625751 "Recent and Pleistocene Coral Reefs of Australia"]. ''J. Geol.'', 58(4: Reef Issue): 330–401. {{Bibcode|1950JG.....58..330F}}. {{doi|10.1086/625751}}. {{JSTOR|30070464}}.
* McNeil, F. S. (July 1954). [https://ajsonline.org/article/58505-organic-reefs-and-banks-and-associated-detrital-sediments "Organic Reefs and Banks and Associated Detrital Sediments"]. ''Amer. J. Sci.'', 252(7): 385–401. {{doi|10.2475/ajs.252.7.385}}.

== External links ==
{{Commons}}
{{Wiktionary}}
* [http://coexploration.org/bbsr/coral/html/body_reef_formation.htm Formation of Bermuda reefs]
* [http://www.stanford.edu/group/microdocs/darwinvolcano.html Darwin's Volcano] – A short video discussing Darwin and Agassiz' coral reef formation debate
* [https://oceanservice.noaa.gov/education/kits/corals/media/supp_coral04a.html NOAA National Ocean Service Education – Coral Atoll Animation]
* [https://oceanservice.noaa.gov/facts/threecorals.html NOAA National Ocean Service – What are the three main types of coral reefs?]
* [https://chromoscience.com/research-article-predicting-coral-recruitment-in-palaus-complex-reef-archipelago/?frame-nonce=cbd595819e Research Article: Predicting Coral Recruitment in Palau's Complex Reef Archipelago]; {{Webarchive|url=https://web.archive.org/web/20210920232708/https://chromoscience.com/research-article-predicting-coral-recruitment-in-palaus-complex-reef-archipelago/?frame-nonce=cbd595819e |date=2021-09-20 }}
* [http://maps.fiu.edu/gis/goldberg/atolls World Atolls, Goldberg 2016: A global map containing all atolls]

{{Corals|state=expanded}}
{{Physical oceanography|expanded=none}}
{{Coastal geography}}

[[Category:Atolls| ]]
[[Category:Biogeomorphology]]
[[Category:Coastal and oceanic landforms]]
[[Category:Islands by type]]
[[Category:Oceanographical terminology]]