Bahama Banks

The Bahama Banks are the submerged carbonate platforms that make up much of the Bahama Archipelago. The term is usually applied in referring to either the Great Bahama Bank around Andros Island, or the Little Bahama Bank of Grand Bahama Island and Great Abaco, which are the largest of the platforms, and the Cay Sal Bank north of Cuba. The islands of these banks are politically part of the Bahamas. Other banks are the three banks of the Turks and Caicos Islands, namely the Caicos Bank of the Caicos Islands, the bank of the Turks Islands, and wholly submerged Mouchoir Bank. Further southeast are the equally wholly submerged Silver Bank and Navidad Bank north of the Dominican Republic.

Bahamabank
The Bahama Banks: Little Bahama Bank in the north and Great Bahama Bank in the south. The Cay Sal Bank is also visible.

Geologic history and structure

The limestone that comprises the Banks has been accumulating since at least the Cretaceous period, and perhaps as early as the Jurassic; today the total thickness under the Great Bahama Bank is over 4.5 kilometres (2.8 miles).[1] As the limestone was deposited in shallow water, the only way to explain this massive column is to estimate that the entire platform has subsided under its own weight at a rate of roughly 3.6 centimetres (2 inches) per 1,000 years.[1]

The waters of the Bahama Banks are very shallow; on the Great Bahama Bank they are generally no deeper than 25 meters (80 feet).[2] The slopes around them however, such as the border of the Tongue of the Ocean in the Great Bahama Bank, are very steep. The Banks were dry land during past ice ages, when sea level was as much as 120 meters (390 feet) lower than at present; the area of the Bahamas today thus represents only a small fraction of their prehistoric extent.[1][2] When they were exposed to the atmosphere, the limestone structure was subjected to chemical weathering that created the caves and sinkholes common to karst terrain, resulting in structures like blue holes.[1]

See also

Links

  • ESA: Earth From Space: The Great Bahamas Bank, on http://spaceref.com, December 20, 2014 11:00 AM

References

  1. ^ a b c d http://geoinfo.amu.edu.pl/wpk/geos/GEO_6/GEO_PLATE_C-16.HTML "Geomorphology from Space, Chapter 6: Coastal Landforms. Plate C-16, 'Great Bahama Bank'" (Accessed 3/9/06)
  2. ^ a b Stephen K. Boss, "Geological Research on the Great Bahama Bank" (Accessed 3/9/06) Archived 2006-02-05 at the Wayback Machine

Further reading

  • Agassiz, Alexander (1894). A Reconnoissance of the Bahamas and of the Elevated Reefs of Cuba in the Steam Yacht "Wild Duck", January to April 1893. pp. 17–18. OCLC 8310508.
  • "The Formation and Distribution of Modern Ooids on Great Bahama Bank". Annual Review of Marine Science. Annual Reviews. 2019. doi:10.1146/annurev-marine-010318-095251.

Coordinates: 24°02′47″N 77°39′05″W / 24.046464°N 77.651367°W

Apulia Carbonate Platform

The Apulia Carbonate Platform in Apulia, Italy was a major palaeogeographic element of the southern margin of the Mesozoic Tethys Ocean. It is one of the so-called peri-Adriatic platforms, which are comparable to the Bahama Banks in their carbonate facies, shape, size, and subsidence rate and, also, in the internal architecture.The Apulia Platform, which is part of the stable and relatively undeformed foreland of the Apennine thrust belt, is bounded on both sides by basinal deposits; westward the margin is buried under the Apennine thrust sheets, to the east the adjacent paleogeographic domains are the vast Ionian Basin to the south and the Umbria-Marche Basin to the north. To the west, the Apulia Platform plunges downfaulted underneath the terrigenous sediments of the Apennine foredeep; to the southeast, the Jurassic–Early Cretaceous margin lies 20–30 km offshore from the present Apulia coastline.

Bahama (disambiguation)

Bahama or Bahamas are the name of the country officially known as The Bahamas

Blue hole

A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock (limestone or coral reef). Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples can be found in South China Sea (Dragon Hole), Belize (Great Blue Hole), the Bahamas (Dean's Blue Hole), Guam, Australia (in the Great Barrier Reef), and Egypt (in the Red Sea).

Blue holes are distinguished from cenotes in that the latter are inland voids usually containing fresh groundwater rather than seawater.

Carbonate platform

A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonous calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually microbes) which induce carbonate precipitation through their metabolism. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others: light, water temperature, transparency and pH-Value. For example, carbonate sedimentation along the Atlantic South American coasts takes place everywhere but at the mouth of the Amazon River, because of the intense turbidity of the water there. Spectacular examples of present-day carbonate platforms are the Bahama Banks under which the platform is roughly 8 km thick, the Yucatan Peninsula which is up to 2 km thick, the Florida platform, the platform on which the Great Barrier Reef is growing, and the Maldive atolls. All these carbonate platforms and their associated reefs are confined to tropical latitudes. Today’s reefs are built mainly by scleractinian corals, but in the distant past other organisms, like archaeocyatha (during the Cambrian) or extinct cnidaria (tabulata and rugosa) were important reef builders.

Cay Sal

Cay Sal (Spanish: Cayo de Sal) is a small island in the Cay Sal Bank between Florida, Cuba, and the Bahamas. It is no longer inhabited.

The Bahamas have an agreement with the U.S. Coast Guard to regularly fly over Cay Sal and other islands in the bank to look for people potentially stranded there.

Cay Sal Bank

Cay Sal Bank (Spanish: Placer de los Roques) is the third largest (after Great Bahama Bank and Little Bahama Bank) and the westernmost of the Bahama Banks. It is located between 23º27'N - 24º10'N and 079º25'W – 080º35'W. In a geographical sense, it is separate from the Bahamas proper as it is much closer to Cuba (from which it is separated by Nicholas Channel, at a distance of 50 km (31 mi)) than to the closest Bahamanian island. It is separated by Santaren Channel from the Great Bahama Bank, the western rim of which is 50 km (31 mi) to the east. The Straits of Florida separate it from the United States mainland and the Florida Keys (Key Largo is 100 km (62 mi) to the north).

Administratively, the bank and its islands are part of Bimini district, the main islands of which are 150 km (93 mi) to the north. The closest point of any other named Bahamian land to the bank is Orange Cay (24°56′24″N 79°08′45″W), the southernmost island of the Bimini Chain. The distance between Orange Cay and the nearest dry land of Cay Sal Bank, the Dog Rocks, is 120 km (75 mi). The westernmost tip of Andros is the second closest point of land, approximately 145 km (90 mi) east of Cay Sal Bank.

Flirt Rocks

Flirt Rocks are two, small, uninhabited rocky islets off of Anguilla, in the Leeward Islands of the Caribbean. They are located 0.75 miles (1.21 km) north of the Prickly Pear Cays. Seal Reef is situated east of the Flirt Rocks.The islets consist of the Great and Little Flirt Rocks. The Great Flirt is approximately 20 feet (6.1 m) above sea level while Little Flirt is approximately 8 feet (2.4 m) to 10 feet (3.0 m) above sea level.

Foss Cross Quarry

Foss Cross Quarry (grid reference SP056092) is a 0.67-hectare (1.7-acre) geological Site of Special Scientific Interest in Gloucestershire, notified in 1972. The site is listed in the 'Cotswold District' Local Plan 2001-2011 (on line) as a Key Wildlife Site (KWS) and a Regionally Important Geological Site (RIGS).

Geography of the Bahamas

The Bahamas are a group of about 700 islands and cays in the western Atlantic Ocean, of which only between 30 and 40 are inhabited. The largest of the islands is Andros Island, located north of Cuba and 200 kilometres (120 miles) southeast of Florida. The Bimini islands are to its northwest. To the North is the island of Grand Bahama, home to the second-largest city in the country, Freeport. The island of Great Abaco is to its east. In the far south is the island of Great Inagua, the second-largest island in the country. Other notable islands include Eleuthera, Cat Island, San Salvador Island, Acklins, Crooked Island, and Mayaguana. Nassau is the capital and largest city, located on New Providence. The islands have a tropical savannah climate, moderated by the Gulf Stream.

The islands are surface projections of the three oceanic Bahama Banks - the Little Bahama Bank, the Great Bahama Bank, and the westernmost Cay Sal Bank. The highest point is only 63 metres (207 feet) above sea level on Cat Island; the island of New Providence, where the capital city of Nassau is located, reaches a maximum elevation of only thirty-seven meters. The land on the Bahamas has a foundation of fossil coral, but much of the rock is oolitic limestone; the stone is derived from the disintegration of coral reefs and seashells. The land is primarily either rocky or mangrove swamp. Low scrub covers much of the surface area. Pineyards are found on four of the northern islands: Grand Bahama, Great Abaco, New Providence, and Andros. On some of the southern islands, low-growing tropical hardwood flourishes. Although some soil is very fertile, it is also very thin. Only a few freshwater lakes and just one river, located on Andros Island, are found in the Bahamas.

Great Bahama Canyon

The Great Bahama Canyon is a V-shaped submarine canyon system in the Bahamas that cuts between the Abaco Islands to the north and Eleuthera island to the south. It separates the Bahama Banks and forms one of the deepest underwater canyon systems known. There are three branches: the Tongue of the Ocean running south between Andros and New Providence, and the northeast and northwest Providence Channel. The canyon walls reach heights of 5 kilometres (3 mi); taller than any canyon walls on land. This canyon system has remained open through a process of submarine erosion.

Gulf Trough

The Gulf Trough, also known as the Suwanee Straits, is an ancient geologic feature of Florida present during the Paleogene period, a period of roughly 42.47 million years. A strong marine current, similar to the Gulf Stream, scoured the trough from southwest to northeast.

Halmos College of Natural Sciences and Oceanography

The Halmos College of Natural Sciences and Oceanography is a natural science college at Nova Southeastern University in Florida. The college offers programs in subjects like biology and mathematics and conducts oceanographical research.

Hornsleasow Quarry

Hornsleasow Quarry (grid reference SP131322) is a 3.5-hectare (8.6-acre) geological Site of Special Scientific Interest in Gloucestershire, notified in 1974. The site is listed in the 'Cotswold District' Local Plan 2001-2011 (on line) as a Regionally Important Geological Site (RIGS).

Long Island, Bahamas

Long Island is an island in the Bahamas that is split by the Tropic of Cancer. It is one of the Districts of the Bahamas and is known as the most scenic island in the Bahamas. Its capital is Clarence Town. The population of Long Island is 3,094 inhabitants.

Old Bahama Channel

The Old Bahama Channel (Spanish: Canal Viejo de Bahama) is a strait of the Caribbean region, between Cuba and the Bahamas.

Oolitic aragonite sand

Oolitic aragonite sand forms in tropical waters. Most of the topography of the Bahama Banks is composed of calcium carbonate oolitic aragonite sand material.

The natural formation through precipitation, sedimentation and possibly microbial activity of aragonite sand in the Bahamas surpasses anyplace else in the world. There are billions of tons of this type of sand material in reserve and millions of tons more created annually.

USCS Varina

USCS Varina was a schooner that served as a survey ship in the United States Coast Survey, a predecessor of the United States Coast and Geodetic Survey, from 1854 to 1875.

Varina was built in 1854 by Fardy Brothers at Baltimore, Maryland. She entered Coast Survey service that year.

On more than one occasion, Varina assisted mariners in distress. In December 1856, at the request of the American consul in Havana, Cuba, Varina called at Nassau on New Providence in the Bahama Islands to take on board the crew and steerage passengers of the American ship Julia Howard, which a short time earlier had wrecked on the Bahama Banks, leaving her crew and passengers destitute at New Providence. Varina transported Julia Howard's crew to Havana, and then took her passengers and any crew who preferred it to Pensacola, Florida.

In February 1858, in response to a request for help by the consignees of the schooner Georgia, which had stranded a few days earlier about 30 nautical miles (56 kilometers) from Pensacola, Varina proceeded to the site of the wreck, but the combined efforts of the crews of Varina and Georgia failed to free Georgia.

On the night of 20 January 1858, Varina was at Pensacola, Florida, when a major fire broke out at the United States Army's Fort Pickens. Her hydrographic party, along with men and boats of the Coast Survey steamer USCS Robert J. Walker, promptly assisted in fighting the fire. The next day, Varina's commanding officer received a communication from Captain John Newton of the Army Corps of Engineers, commanding the harbor of Pensacola, acknowledging the important firefighting service rendered by Varina.

On the morning of 21 February 1860, the Russian bark Vesta ran aground on the north breaker at the Ossabaw entrance to the Savannah River off the coast of Georgia and was wrecked. Varina took Vesta's officers and crew aboard and gave them shelter for the night, and Varina's crew was able to assist in ultimately saving Vesta's cargo and stores for Vesta's and the cargo's owners. The Russian vice consul at Savannah acknowledged Varina's assistance to Vesta.

Varina was retired from Coast Survey service in 1875.

USS Isonomia

USS Isonomia was a steamship in the United States Navy during the American Civil War.

Formerly Shamrock, Isonomia was purchased at New York from Charles S. Leary on 16 July 1864. She was commissioned at New York Navy Yard on 16 August 1864, Lieutenant Commander E. Simpson in command.

West End, Grand Bahama

West End (also referred to as "Settlement Point") is the oldest town and westernmost settlement on the Bahamian island of Grand Bahama. It is the current capital of Grand Bahama, contrary to the popular belief that Freeport City is the capital of the island. It is also the third largest settlement in the Bahamas. There is one airport in West End, West End Airport, which serves mostly private aircraft. Since the 1950s, the settlement of West End has fluctuated with the rise and fall of the adjacent resort developments.

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