The Telegraph Plateau is a region of the North Atlantic that was supposedly relatively flat and shallow compared to the rest of the ocean away from shore. The term is archaic and no longer used by hydrographers. It was so named because it seemed to be an ideal route for a transatlantic telegraph cable, and was actually used for the first such cable in 1858. The Victorian hydrographers surveying the route failed to notice the Mid-Atlantic Ridge in the middle of the route.
The feature was discovered by Matthew Fontaine Maury while producing a bathymetric chart of the ocean in 1853, compiled from sounding data from multiple ships' logs. Maury so named it because he thought it would be an ideal route for a transatlantic telegraph cable, which at the time, was no more than a vague aspiration. [1] His hydrographers confirmed his assessment of the viability of the route using accurate sounders invented by John Mercer Brooke. [2] Brooke's sounder was designed to release the lead immediately it contacted the bottom so that a sample of the sea bed could be recovered without the risk of the line breaking while it was being hauled back up due to the weight of the lead. Maury had discarded many of the historic readings because he thought they were inaccurate due to the inability of the sounder to tell when the lead had contacted the bottom in deep ocean. This resulted in more line being run out before the reading was taken. Maury's solution to this problem was to determine the law of descent of the line for given sizes of line and weights of lead. Sounders were provided with tables of expected rates of line runout, so that once the rate was much less than that expected, they knew that the bottom had been reached. [3]
The feature occupied the shortest route between the British Isles and the Americas. [4] The region begins at around 51° north [5] and runs from near the south of Ireland to Newfoundland in Canada north of the Great Banks for a distance of 1,400 miles (2,300 km). Its average depth was measured at 1,400 fathoms (2,600 m), and greatest depth 2,500 fathoms (4,600 m). [6] It was described as a table-land or steppe (in comparison to the Southern Andean Steppe), [7] and sometimes called the Atlantic steppe. [8] To the south of the plateau, the hydrography was determined to be very uneven, with depths of between 4 and 6 miles (6,400 and 9,700 m) recorded, [9] although six miles is a little beyond any depth marked on a modern chart. [10]
Maury's chart was instrumental in Cyrus Field's decision to land the transatlantic cable in Newfoundland. It showed that the region to the south of Telegraph Plateau was much too rugged to take a cable directly to the United States. [11] The route had appeal, not only because it was flat, not too deep, and was the shortest route, but also because it had moderate currents which would help the cable to sink straight down and a soft seabed (made up of microscopic shells) for the cable to rest on. [12]
The Victorian hydrographers failed to detect the presence of the Mid-Atlantic Ridge due to the widely spaced soundings taken along the proposed cable route. The ridge is particularly narrow at this point and the hydrography on either side is relatively flat. The term Telegraph Plateau is no longer used by modern hydrographers. [13]
Telegraph Plateau consists of oceanic crust plus a section of the Reykjanes Ridge (the northern branch of the Mid-Atlantic Ridge) where the plateau crosses from the Eurasian Plate to the North American Plate. The crossing is in the Charlie-Gibbs Fracture Zone between the Minia Seamount Mountains to the north and the volcanic Faraday Hills to the south. [14] Telegraph Plateau was once thought to be an ancient shield resembling Greenland with a different strike, and the fold belts around it suggested Caledonian folding. [15] These features are now known to be much more recent and are a result of plate tectonics. [16]
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858.
The Challenger expedition of 1872–1876 was a scientific programme that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, HMS Challenger.
The Mid-Atlantic Ridge is a mid-ocean ridge located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North American from the Eurasian Plate and the African Plate, north and south of the Azores Triple Junction respectively. In the South Atlantic, it separates the African and South American plates. The ridge extends from a junction with the Gakkel Ridge northeast of Greenland southward to the Bouvet Triple Junction in the South Atlantic. Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level, for example in Iceland. The ridge has an average spreading rate of about 2.5 centimetres (1 in) per year.
Transatlantic telegraph cables were undersea cables running under the Atlantic Ocean for telegraph communications. Telegraphy is now an obsolete form of communication, and the cables have long since been decommissioned, but telephone and data are still carried on other transatlantic telecommunications cables. The first cable was laid in the 1850s from Valentia Island off the west coast of Ireland to Bay of Bulls, Trinity Bay, Newfoundland. The first communications occurred on 16 August 1858, but the line speed was poor, and efforts to improve it caused the cable to fail after three weeks.
Transatlantic crossings are passages of passengers and cargo across the Atlantic Ocean between Europe or Africa and the Americas. The majority of passenger traffic is across the North Atlantic between Western Europe and North America. Centuries after the dwindling of sporadic Viking trade with Markland, a regular and lasting transatlantic trade route was established in 1566 with the Spanish West Indies fleets, following the voyages of Christopher Columbus.
A bathymetric chart is a type of isarithmic map that depicts the submerged topography and physiographic features of ocean and sea bottoms. Their primary purpose is to provide detailed depth contours of ocean topography as well as provide the size, shape and distribution of underwater features. Topographic maps display elevation above ground and are complementary to bathymetric charts. Charts use a series of lines and points at equal intervals to showcase depth or elevation. A closed shape with increasingly smaller shapes inside of it can indicate an ocean trench or a seamount, or underwater mountain, depending on whether the depths increase or decrease going inward.
The Celtic Sea is the area of the Atlantic Ocean off the southern coast of Ireland bounded to the east by Saint George's Channel; other limits include the Bristol Channel, the English Channel, and the Bay of Biscay, as well as adjacent portions of Wales, Cornwall, and Brittany. The southern and western boundaries are delimited by the continental shelf, which drops away sharply. The Isles of Scilly are an archipelago of small islands in the sea.
The All Red Line was a system of electrical telegraphs that linked much of the British Empire. It was inaugurated on 31 October 1902. The informal name derives from the common practice of colouring the territory of the British Empire red or pink on political maps.
The United Kingdom Hydrographic Office (UKHO) is the UK's agency for providing hydrographic and marine geospatial data to mariners and maritime organisations across the world. The UKHO is a trading fund of the Ministry of Defence (MoD) and is located in Taunton, Somerset, with a workforce of approximately 900 staff.
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.
Admiralty charts are nautical charts issued by the United Kingdom Hydrographic Office (UKHO) and subject to Crown Copyright. Over 3,500 Standard Nautical Charts (SNCs) and 14,000 Electronic Navigational Charts (ENCs) are available with the Admiralty portfolio offering the widest official coverage of international shipping routes and ports, in varying detail.
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The Naval Oceanographic Office (NAVOCEANO), located at John C. Stennis Space Center in south Mississippi, comprises approximately 1,000 civilian, military and contract personnel responsible for providing oceanographic products and services to all elements within the Department of Defense.
Telecommunications in Newfoundland and Labrador have been important due to the province's rural and remote geography. They are also well-situated to be the terminus of transatlantic undersea communication cables since it was found by Lieutenant O.H. Berryman in 1853 that they are connected to Ireland by a plateau at a depth of 1500 to 2000 fathoms which is highly suitable for this purpose.
The following outline is provided as an overview of and introduction to Oceanography.
The Blake Plateau lies in the western Atlantic Ocean off the southeastern United States coasts of North Carolina, South Carolina, Georgia and Florida. The Blake Plateau lies between the North American continental shelf and the deep ocean basin extending about 145 kilometers east and west by 170 kilometers north and south, with a depth of about 500 meters inshore sloping to about 1,000 meters about 375 kilometers off shore, where the Blake Escarpment drops steeply to the deep basin. The Blake Plateau, associated Blake Ridge and Blake Basin are named for the U.S. Coast and Geodetic Survey steamer USC&GS George S. Blake, in service 1874–1905, that first used steel cable for oceanographic operations and pioneered deep ocean and Gulf Stream exploration. Survey lines of the steamer George S. Blake first defined the plateau that now bears the ship's name.
Rear-Admiral George Stephen Ritchie CB DSC was a British admiral noted for his cartographic and hydrographic work.
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