Information on Atolls

The word atoll comes from the Dhivehi (an Indo-Aryan language spoken on the Maldive Islands) word atholhu (Dhivehi: އަތޮޅު, [ˈət̪ɔɭu])OED. Its first recorded use in English was in 1625 as atollon. However, the term was created by Charles Darwin (1842, p. 2), who described atolls as the final stage in oceanic island development. More modern definitions of atoll are those of McNeil (1954, p. 396) as "..an annular reef enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus" and Fairbridge (1950, p. 341) "...in an exclusively morphological sense, [as] ...a ring-shaped ribbon reef enclosing a lagoon."
Reef-building corals will thrive only in warm tropical and subtropical waters of oceans and seas, and therefore atolls are only found in the tropics and subtropics. The northernmost atoll of the world Kure Atoll at 28°24' N, along with other atolls of the Northwestern Hawaiian Islands. The southernmost atolls of the world are Elizabeth Reef at 29°58' S, and nearby Middleton Reef at 29°29' 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°40' S. Bermuda is sometimes claimed as the "northernmost atoll" at a latitude of 32°24' N. At this latitude coral reefs would not develop without the warming waters of the Gulf Stream. However, Bermuda is what is termed a pseudo-atoll because its general form, while resembling that of an atoll, has a very different mode of formation. While there is no atoll directly on the Equator, the closest atoll to the Equator is Aranuka of Kiribati, with its southern tip just 12 km North of the Equator.

The largest atolls by total area (lagoon plus reef and dry land)[2] are listed below:

Saya de Malha Bank, Western Indian Ocean (35000 km²) (without separate North Bank), submerged, least depth 7 m,

Lansdowne Bank, west of New Caledonia (21000 km²), submerged, least depth 3.7 m [1]

Great Chagos Bank (12642 km², land area only 4.5 km²)

Reed Bank, Spratly Islands (8866 km²), submerged, least depth 9 m

Macclesfield Bank, South China Sea (6448 km²), submerged, least depth 9.2 m

North Bank (Ritchie Bank, north of Saya de Malha Bank) (5800 km²), submerged, least depth <10 m

Cay Sal Bank, Bahamas (5226.73 km², small land area of 14,87 km²)

Rosalind Bank, Caribbean Sea (4500 km²), submerged, least depth 7.3 m

Boduthiladhunmathi (Thiladhunmathi-Miladhunmadulu) Atoll, Maldives, (two names, but a single atoll structure) (3850 km², land area 51 km²)

Chesterfield Islands, New Caledonia (3500 km², land area <10 km²)

Huvadhu Atoll, Maldives (3152 km², land area 38.5 km²)

Truk Lagoon, Chuuk (3130 km²)[2]

Sabalana Islands, Indonesia (2694 km²)

Nukuoro atoll, Federated States of Micronesia, lagoon, is 40 km², land area of 1.7 km², divided among more than 40 islets that lie on the northern, eastern and southern sides of the lagoon

Lihou Reef, Coral Sea (2529 km², land area 1 km²)

Bassas de Pedro (2474,33 km²), submerged, least depth 16.4 m

Ardasier Bank, Spratly Islands (2347 km²), cay on the south side?

Kwajalein, Marshall Islands (2304 km², land area 16.4 km²)

Diamond Islets Bank, Coral Sea (2282 km², land area <1 km²)

Namonuito Atoll, Chuuk (2267 km², land area 4.4 km²)

Ari Atoll, Maldives (2252 km², land area 69 km²)

Maro Reef, Northwestern Hawaiian Islands, 1934 km²

Rangiroa, Tuamotu Islands (1762 km², land area 79 km²)

Kolhumadulhu Atoll, Maldives (1617 km², land area 79 km²)

North Malé Atoll, Maldives (1565 km², land area 69 km²)

Ontong Java, Solomon Islands (1500 km², land area 12 km²)

In most cases, the land area of an atoll is very small in comparison to the total area. According to [3], Lifou (land area 1146 km²) is the largest raised coral atoll of the world, followed by Rennell Island (660 km²). More sources however list as the largest atoll in the world in terms of land area Kiritimati, which is also a raised coral atoll (321.37 km² land area; according to other sources even 575 km²), 160 km² main lagoon, 168 km² other lagoons (according to other sources 319 km² total lagoon size). The remains of an ancient atoll as a hill in a limestone area is called a reef knoll. The second largest atoll by dry land area is Aldabra with 155 km². The largest atoll in terms of island numbers is Huvadhu Atoll in the south of the Maldives with 255 islands.

Formation

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 900 feet (270 m) 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.
Coral atolls are also an important place where dolomitization of calcite occurs. At certain depths water is undersaturated in calcium carbonate but saturated in dolomite. Convection created by tides and sea currents enhance this change. Hydrothermal currents created by volcanoes under the atoll may also play an important role.

Video's on how Atolls are formed:
Darwins Theory  

Kiribati Republic

Kiribati (pronounced /ˈkɪrɨbæs/ ( listen) KIRR-i-bas;[3] Gilbertese: [ˈkiɾibas]), officially the Republic of Kiribati, is an island nation located in the central tropical Pacific Ocean. It is composed of 32 atolls and one raised coral island, dispersed over 3,500,000 square kilometres, (1,351,000 square miles) straddling the equator, and bordering the International Date Line to the east. The name Kiribati is the local pronunciation of "Gilberts", derived from the main island chain, the Gilbert Islands. Kiribati became independent from the United Kingdom in 1979. It is a member of the Commonwealth of Nations, the IMF and the World Bank, and became a full member of the United Nations in 1999.

Banaba Island

Banaba Island (pronounced /bəˈnɑːbə/) (also Ocean Island), an island in the Pacific Ocean, is a solitary raised coral island west of the Gilbert Island chain and 300 km east of Nauru. It is part of the Republic of Kiribati. It has an area of 6.5 km², and the highest point on the island is also the highest point in Kiribati, at 81 metres (266 ft) high. Along with Nauru and Makatea ( French Polynesia ), it is one of the important elevated phosphate islands of the Pacific.

I found this great resourceful site for Banaba Island and on there is are a couple of these topics:
http://www.banaban.com/

Abara Banaba Information


Banaba Environmental Issues:
Phosephate Mining on Banaba

Christmas Island

Image: Flying Fish Cove from Territory Day Park, Christmas Island, Indian Ocean. External Territory of Australia

Some stats on the Island:

The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located 2,600 kilometres (1,600 mi) northwest of the Western Australian city of Perth, 500 km (310 mi) south of the Indonesian capital, Jakarta, and 975 km (606 mi) ENE of the Cocos (Keeling) Islands.
It has a population of 1,403 residents who live in a number of "settlement areas" on the northern tip of the island: Flying Fish Cove (also known as Kampong also is their capital city), Silver City, Poon Saan, and Drumsite.
The island’s geographic isolation and history of minimal human disturbance has led to a high level of endemism amongst its flora and fauna, which is of significant interest to scientists and naturalists.
Phosphate, deposited as guano, has been mined on the island for many years. 63% of its 135 square kilometres (52 sq mi) is an Australian national park. There exists large areas of primary rainforest.

Phosphate mining had been the only significant economic activity, but in December 1987 the Australian Government closed the mine. In 1991, the mine was reopened by a consortium which included many of the former mine workers as shareholders. With the support of the government, a $34 million casino opened in 1993, but was closed in 1998 and has not re-opened. The Australian Government in 2001 agreed to support the creation of a commercial spaceport on the island, however this has not yet been constructed, and appears that it will not proceed in the future. The Howard Government built a temporary immigration detention centre on the island in 2001 and planned to replace it with a larger, modern facility located at North West Point until Howard's defeat in the 2007 elections

Christmas Island is of immense scientific value as it was uninhabited until the late nineteenth century, so many unique species of fauna and flora exist which have evolved independently of human interference. Two species of native rats, the Maclear's and Bulldog Rat, have gone extinct since the island was settled. The endemic shrew has not been seen since the mid 1980s and may be already extinct, and the Christmas Island Pipistrelle, a small bat, is critically endangered and possibly also extinct. Two-thirds of the island has been declared a National Park which is managed by the Australian Department of Environment and Heritage through Parks Australia.

The dense rainforest has evolved in the deep soils of the plateau and on the terraces. The forests are dominated by twenty-five tree species. Ferns, orchids and vines grow on the branches in the humid atmosphere beneath the canopy. The 135 plant species include sixteen which are found only on Christmas Island.

The annual red crab mass migration (around 100 million animals) to the sea to spawn has been called one of the wonders of the natural world and takes place each year around November; after the start of the wet season and in synchronisation with the cycle of the moon.

The land crabs and sea birds are the most noticeable animals on the island. Twenty terrestrial and intertidal species of crab (of which thirteen are regarded as true land crabs, only dependent on the ocean for larval development) have been described. Robber crabs, known elsewhere as coconut crabs, also exist in large numbers on the island.

Christmas Island is a focal point for sea birds of various species. Eight species or subspecies of sea birds nest on the island. The most numerous is the Red-footed Booby that nests in colonies, in trees, on many parts of the shore terrace. The widespread Brown Booby nests on the ground near the edge of the seacliff and inland cliffs. Abbott's Booby (listed as endangered) nests on tall emergent trees of the western, northern and southern plateau rainforest. The Christmas Island forest is the only nesting habitat of the Abbott's Booby left in the world. The endemic Christmas Island Frigatebird (listed as endangered) has nesting areas on the north-eastern shore terraces and the more widespread. Great Frigatebirds nest in semi-deciduous trees on the shore terrace with the greatest concentrations being in the North West and South Point areas. The Common Noddy and two species of bosuns or tropicbirds, with their brilliant gold or silver plumage and distinctive streamer tail feathers, also nest on the island.

Of the ten native land birds and shorebirds, seven are endemic species or subspecies. This includes the Christmas Island Thrush, and the Christmas Island Imperial Pigeon. Some 86 migrant bird species have been recorded as visitors to the Island