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 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 a ...

, and was actually used for the first such cable in 1858. The Victorian hydrographers surveying the route failed to notice the

Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) 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 ...

in the middle of the route.

Discovery and naming

FMIB 49307 Brooke's Deep-Sea Sounding Apparatus

The feature was discovered by

Matthew Fontaine Maury Matthew Fontaine Maury (January 14, 1806February 1, 1873) was an American oceanographer and naval officer, serving the United States and then joining the Confederacy during the American Civil War. He was nicknamed "Pathfinder of the Seas" and i ...

while producing a

bathymetric chart 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, ...

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

, which at the time, was no more than a vague aspiration. His hydrographers confirmed his assessment of the viability of the route using accurate sounders invented by John Mercer Brooke. Brooke's sounder was designed to release the

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

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

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. The feature occupied the shortest route between the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

and the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

. The region begins at around 51° north and runs from near the south of Ireland to Newfoundland in Canada north of the Great Banks for a distance of . Its average depth was measured at , and greatest depth . It was described as a table-land or steppe (in comparison to the

Southern Andean Steppe The Southern Andean steppe is a montane grasslands and shrublands ecoregion occurring along the border of Chile and Argentina in the high elevations of the southern Andes mountain range. Setting This ecoregion is found from in the north to in t ...

), and sometimes called the ''Atlantic steppe''. To the south of the plateau, the

hydrography Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primar ...

was determined to be very uneven, with depths of between recorded, although six miles is a little beyond any depth marked on a modern chart. Maury's chart was instrumental in

Cyrus Field Cyrus West Field (November 30, 1819July 12, 1892) was an American businessman and financier who, along with other entrepreneurs, created the Atlantic Telegraph Company and laid the first telegraph cable across the Atlantic Ocean in 1858. Early ...

'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. 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. The Victorian hydrographers failed to detect the presence of the

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.

Geology

Telegraph Plateau consists of

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

plus a section of the

Reykjanes Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) 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 Am ...

(the northern branch of the Mid-Atlantic Ridge) where the plateau crosses from the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

to the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

. The crossing is in the

Charlie-Gibbs Fracture Zone Charlie-Gibbs Fracture Zone is a system of two parallel fracture zones. It is the most prominent interruption of the Mid-Atlantic Ridge between the Azores and Iceland. It can be traced over more than 2000 kilometers, all the way from north-eas ...

between the Minia Seamount Mountains to the north and the volcanic Faraday Hills to the south. Telegraph Plateau was once thought to be an ancient shield resembling

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...

with a different

strike Strike may refer to: People * Strike (surname) Physical confrontation or removal *Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm *Airstrike, military strike by air forces on either a suspected ...

, and the fold belts around it suggested

Caledonian folding The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that ...

. These features are now known to be much more recent and are a result of

plate tectonics Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

.Furlong ''et al.'', p. 82

References

Bibliography

* Barnes, Clifford A.; Broadus, James M.; Ericson, David Barnard; Fleming, Richard Howell; LaMourie, Matthew J.; Namias, Jerome
"Atlantic Ocean"
''Encyclopædia Britannica'' (online), Encyclopædia Britannica, Inc., retrieved 26 May 2020. * Kevin P. Furlong, Steven D. Sheaffer, Rocco Malservisi, "Thermal–rheological controls of deformation within ocean transforms", pp. 65–84 in, ''The Nature and Tectonic Significance of Fault Zone Weakening'', Geological Society of London, 2001 . * John Mullaly, ''The Laying of the Cable, or the Ocean Telegraph'', D. Appleton, 1858, . * Helen M. Rozwadowski, ''Fathoming the Ocean: The Discovery and Exploration of the Deep Sea'', Harvard University Press, 2009 . * Jacob Ward
"Oceanscapes and spacescapes in North Atlantic communications: Laying cables"
ch. 10 in, Jon Agar, Jacob Ward (eds), Robert E. Holdsworth, R. A. Strachan, J. Magloughlin, R. J. Knipe (eds), ''Histories of Technology, the Environment and Modern Britain'', UCL Press, retrieved 8 May 2020. * N. Zhirov, ''Atlantis: Atlantology: Basic Problems'', University Press of the Pacific, 2001 (1970 reprint) . {{coord missing, Atlantic Ocean Plateaus of the Atlantic Ocean Marine geology Telegraphy