Guyot

Last updated
The Bear Seamount (left), a guyot in the northern Atlantic Ocean Bear Seamount guyot.jpg
The Bear Seamount (left), a guyot in the northern Atlantic Ocean

In marine geology, a guyot (pronounced /ɡˈj/ ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than 200 m (660 ft) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi). [1] Guyots are most commonly found in the Pacific Ocean, but they have been identified in all the oceans except the Arctic Ocean.

Marine geology The study of the history and structure of the ocean floor

Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.

Seamount A mountain rising from the ocean seafloor that does not reach to the waters surface

A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface, and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to 1,000–4,000 m (3,300–13,100 ft) in height. They are defined by oceanographers as independent features that rise to at least 1,000 m (3,281 ft) above the seafloor, characteristically of conical form. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface such flat-top seamounts are called "guyots" or "tablemounts"

Pacific Ocean Ocean between Asia and Australia in the west, the Americas in the east and Antarctica or the Southern Ocean in the south.

The Pacific Ocean is the largest and deepest of Earth's oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west and the Americas in the east.

Contents

History

Guyots were first recognized in 1945 by Harry Hammond Hess, who collected data using echo-sounding equipment on a ship he commanded during World War II. [2] His data showed that some undersea mountains had flat tops. Hess called these undersea mountains "guyots", because they resembled the flat-roofed biology and geology building at Princeton University, Guyot Hall, named after the 19th-century geographer Arnold Henry Guyot. [3] Hess postulated they were once volcanic islands that were beheaded by wave action, yet they are now deep under sea level. This idea was used to help bolster the theory of plate tectonics. [2]

Harry Hammond Hess was a geologist and a United States Navy officer in World War II.

World War II 1939–1945 global war

World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

Princeton University is a private Ivy League research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the nine colonial colleges chartered before the American Revolution. The institution moved to Newark in 1747, then to the current site nine years later, and renamed itself Princeton University in 1896.

Formation

Guyots show evidence of having once been above the surface, with gradual subsidence through stages from fringed reefed mountain, coral atoll, and finally a flat-topped submerged mountain. [1] Seamounts are made by extrusion of lavas piped upward in stages from sources within the Earth's mantle, usually hotspots, to vents on the seafloor. The volcanism invariably ceases after a time, and other processes dominate. When an undersea volcano grows high enough to be near or breach the ocean surface, wave action and/or coral reef growth tend to create a flat-topped edifice. However, all ocean crust and guyots form from hot magma and/or rock, which cools over time. As the lithosphere that the future guyot rides on slowly cools, it becomes denser and sinks lower into Earth's mantle, through the process of isostasy.

Subsidence the motion of a surface (usually, the Earths surface) as it shifts downward relative to a datum such as sea-level

Subsidence is the sudden sinking or gradual downward settling of the ground's surface with little or no horizontal motion. The definition of subsidence is not restricted by the rate, magnitude, or area involved in the downward movement. It may be caused by natural processes or by human activities. The former include various karst phenomena, thawing of permafrost, consolidation, oxidation of organic soils, slow crustal warping, normal faulting, caldera subsidence, or withdrawal of fluid lava from beneath a solid crust. The human activities include sub-surface mining or extraction of underground fluids, e. g. petroleum, natural gas, or groundwater. Ground subsidence is of global concern to geologists, geotechnical engineers, surveyors, engineers, urban planners, landowners, and the public in general.

Reef A bar of rock, sand, coral or similar material, lying beneath the surface of water

A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock outcrops, etc.—but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.

Coral Marine invertebrates of the class Anthozoa

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically live in compact colonies of many identical individual polyps. Corals species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

This is the same process that gives rise to higher seafloor topography at oceanic ridges, such as the Mid-Atlantic Ridge in the Atlantic Ocean, and deeper ocean at abyssal plains and oceanic trenches, such as the Mariana Trench. Thus, the island or shoal that will eventually become a guyot slowly subsides over millions of years. In the right climatic regions, coral growth can sometimes keep pace with the subsidence, resulting in coral atoll formation, but eventually the corals dip too deep to grow and the island becomes a guyot. The greater the amount of time that passes, the deeper the guyots become. [4]

Mid-Atlantic Ridge A divergent tectonic plate boundary that in the North Atlantic separates the Eurasian and North American plates, and in the South Atlantic separates the African and South American plates

The Mid-Atlantic Ridge (MAR) is a mid-ocean ridge, a divergent tectonic plate 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 it separates the Eurasian and North American plates, and 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. The section of the ridge that includes Iceland is known as the Reykjanes Ridge. The ridge has an average spreading rate of about 2.5 centimetres (0.98 in) per year.

Atlantic Ocean Ocean between Europe, Africa and the Americas

The Atlantic Ocean is the second largest of the world's oceans, with an area of about 106,460,000 square kilometers. It covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. It separates the "Old World" from the "New World".

Abyssal plain Flat area on the deep ocean floor

An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 metres (9,800 ft) and 6,000 metres (20,000 ft). Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins.

Seamounts provide data on movements of tectonic plates on which they ride, and on the rheology of the underlying lithosphere. The trend of a seamount chain traces the direction of motion of the lithospheric plate over a more or less fixed heat source in the underlying asthenosphere, the part of the Earth's mantle beneath the lithosphere. [5] There are thought to be up to an estimated 50,000 seamounts in the Pacific basin. [6] The Hawaiian–Emperor seamount chain is an excellent example of an entire volcanic chain undergoing this process, from active volcanism, to coral reef growth, to atoll formation, to subsidence of the islands and becoming guyots.

Rheology is the study of the flow of matter, primarily in a liquid state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. It is a branch of physics which deals with the deformation and flow of materials, both solids and liquids.

Lithosphere The rigid, outermost shell of a terrestrial-type planet or natural satellite that is defined by its rigid mechanical properties

A lithosphere is the rigid, outermost shell of a terrestrial-type planet, or natural satellite, that is defined by its rigid mechanical properties. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater. The outermost shell of a rocky planet, the crust, is defined on the basis of its chemistry and mineralogy.

Asthenosphere The highly viscous, mechanically weak and ductile region of the Earths upper mantle

The asthenosphere is the highly viscous, mechanically weak and ductilely deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km below the surface. The Lithosphere–asthenosphere boundary is usually referred to as LAB. The asthenosphere is almost solid, although some of its regions could be molten. The lower boundary of the asthenosphere is not well defined. The thickness of the asthenosphere depends mainly on the temperature. However, the rheology of the asthenosphere also depends on the rate of deformation, which suggests that the asthenosphere could be also formed as a result of a high rate of deformation. In some regions the asthenosphere could extend as deep as 700 km (430 mi). It is considered the source region of mid-ocean ridge basalt (MORB).

Characteristics

The steepness gradient of most guyots is about 20 degrees. To technically be considered a guyot or tablemount, they must stand at least 900 m (3,000 ft) tall. [7] One guyot in particular, the Great Meteor Tablemount in the Northeast Atlantic Ocean, stands at more than 4,000 m (13,000 ft) high, with a diameter of 110 km (68 mi). [8] However, there are many undersea mounts that can range from just less than 90 m (300 ft) to around 900 m (3,000 ft). [7] Very large oceanic volcanic constructions, hundreds of kilometres across, are called oceanic plateaus. [9] Guyots are much larger in area (mean of 3,313 km2) than typical seamounts (mean area of 790 km2). [10]

Great Meteor Seamount A large guyot in the Southern Azores Seamount Chain

The Great Meteor Seamount, also called the Great Meteor Tablemount, is a guyot and the largest seamount in the North Atlantic with a volume of 24,000 km3 (5,800 cu mi). It is one of the Seewarte Seamounts, rooted on a large terrace located south of the Azores Plateau. The crust underlying Great Meteor has an age of 85 million years, deduced from the magnetic anomaly 34 (An34) at this location.

Oceanic plateau Relatively flat submarine region that rises well above the level of the ambient seabed

An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.

There are 283 guyots in the world's oceans, with the North Pacific having 119, South Pacific 77, South Atlantic 43, Indian Ocean 28, North Atlantic 8, Southern Ocean 6, and the Mediterranean 2 guyots; there are none in the Arctic Ocean, though one is found along the Fram Strait in northeastern Greenland. [11] Guyots are also associated with specific lifeforms and varying amounts of organic matter. Local increases in chlorophyll a, enhanced carbon incorporation rates and changes in phytoplankton species composition were associated with the seamount. [12]

See also

Related Research Articles

Divergent boundary Linear feature that exists between two tectonic plates that are moving away from each other

In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill.

Convergent boundary Region of active deformation between colliding lithospheric plates

Convergent boundaries are areas on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other causing a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Benioff Zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

Hawaiian–Emperor seamount chain A mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii.

The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean. The seamount chain, containing over 80 identified undersea volcanoes, stretches over 5,800 kilometres (3,600 mi) from the Aleutian Trench in the far northwest Pacific to the Loʻihi seamount, the youngest volcano in the chain, which lies about 35 kilometres (22 mi) southeast of the Island of Hawaiʻi.

Ridge push or sliding plate force is a proposed driving force for plate motion in plate tectonics that occurs at mid-ocean ridges as the result of the rigid lithosphere sliding down the hot, raised asthenosphere below mid-ocean ridges. Although it is called ridge push, the term is somewhat misleading; it is actually a body force that acts throughout an ocean plate, not just at the ridge, as a result of gravitational pull. The name comes from earlier models of plate tectonics in which ridge push was primarily ascribed to upwelling magma at mid-ocean ridges pushing or wedging the plates apart.

Mid-ocean ridge An underwater mountain system formed by plate tectonic spreading

A mid-ocean ridge (MOR) is an underwater mountain system formed by plate tectonics. It consists of various mountains linked in chains, typically having a valley known as a rift running along its spine. This type of oceanic mountain ridge is characteristic of what is known as an 'oceanic spreading center', which is responsible for seafloor spreading. The production of new seafloor results from mantle upwelling in response to plate spreading; this isentropic upwelling solid mantle material eventually exceeds the solidus and melts. The buoyant melt rises as magma at a linear weakness in the oceanic crust, and emerges as lava, creating new crust upon cooling. A mid-ocean ridge demarcates the boundary between two tectonic plates, and consequently is termed a divergent plate boundary.

Hawaii hotspot A volcanic hotspot located near the Hawaiian Islands, in the northern Pacific Ocean

The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the most well-known and heavily studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian – Emperor seamount chain, a chain of volcanoes over 5,800 kilometres (3,600 mi) long. Four of these volcanoes are active, two are dormant, and more than 123 are extinct, many having since been ground beneath the waves by erosion as seamounts and atolls. The chain extends from south of the island of Hawaiʻi to the edge of the Aleutian Trench, near the eastern edge of Russia.

This is a list of articles related to plate tectonics and tectonic plates.

Macdonald hotspot hotspot in the Pacific Ocean

The Macdonald hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of the Macdonald Seamount, and possibly the Austral-Cook Islands chain. It probably did not generate all of the volcanism in the Austral and Cook Islands as age data imply that several additional hotspots were needed to generate some volcanoes.

Geology of the Pacific Ocean

The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.

The Mid-Pacific Mountains (MPM) is a large oceanic plateau located in the central North Pacific Ocean or south of the Hawaiian–Emperor seamount chain. Of volcanic origin and Mesozoic in age, it is located on the oldest part of the Pacific Plate and rises up to 2 km (1.2 mi) above the surrounding ocean floor and is covered with several layers of thick sedimentary sequences that differ from those of other plateaux in the North Pacific. About 50 seamounts are distributed over the MPM. Some of the highest points in the range are above sea level which include Wake Island and Marcus Island.

Discovery Seamounts are a chain of seamounts in the Southern Atlantic Ocean, which include the Discovery Seamount. The seamounts lie 850 kilometres (530 mi) east of Gough Island and once rose above sea level. Various volcanic rocks as well as glacial dropstones and sediments have been dredged from the seamounts.

Wōdejebato A guyot in the Marshall Islands northwest of the smaller Pikinni Atoll

Wōdejebato is a Cretaceous guyot or tablemount in the northern Marshall Islands, Pacific Ocean. Wōdejebato is probably a shield volcano and is connected through a submarine ridge to the smaller Pikinni Atoll 74 kilometres (46 mi) southeast of the guyot; unlike Wōdejebato, Pikinni rises above sea level. The seamount rises for 4,420 metres (14,500 ft) to 1,335 metres (4,380 ft) depth and is formed by basaltic rocks. The name Wōdejebato refers to a sea god of Pikinni.

Limalok A Cretaceous-Paleocene guyot in the Marshall Islands

Limalok is a Cretaceous-Paleocene guyot/tablemount in the southeastern Marshall Islands, one of a number of seamounts in the Pacific Ocean. It was probably formed by a volcanic hotspot in present-day French Polynesia. Limalok lies southeast of Mili Atoll and Knox Atoll, which rise above sea level, and is joined to each of them through a volcanic ridge. It is located at a depth of 1,255 metres (4,117 ft) and has a summit platform with an area of 636 square kilometres (246 sq mi).

Lo-En An Albian-Campanian guyot in the Marshall Islands in the Pacific Ocean

Lo-En or Hess is an Albian-Campanian guyot in the Marshall Islands. One among a number of seamounts in the Pacific Ocean, it was probably formed by a hotspot in what is present-day French Polynesia. Limalok lies southeast of Eniwetok which rise above sea level and Lo-En is almost connected to it through a ridge.

Ita Mai Tai seamount in the Pacific Ocean

Ita Mai Tai is a Cretaceous-early Cenozoic seamount northwest of the Marshall Islands and north of Micronesia. One among a number of seamounts in the Pacific Ocean, it is part of the Magellan Seamounts which may have a hotspot origin although Ita Mai Tai itself may not have formed on a hotspot.

Rarotonga hotspot

The Rarotonga hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of Rarotonga and some volcanics of Aitutaki.

Horizon Guyot

Horizon Guyot is a presumably Cretaceous guyot/tablemount in the Mid-Pacific Mountains, Pacific Ocean. It is an over 300 kilometres (190 mi) long elongated ridge that stretches in northeast-southwest direction and has two flat tops; it rises 4.3 kilometres (2.7 mi) to a minimum depth 1,443 metres (4,734 ft). The Mid-Pacific Mountains and thus also Horizon Guyot lie west of Hawaii and northeast of the Line Islands.

Allison Guyot Seamount in the Pacific Ocean

Allison Guyot is a tablemount (guyot) in the underwater Mid-Pacific Mountains of the Pacific Ocean. It is a trapezoidal flat mountain rising 1,500 metres above the seafloor to a depth of less than 1,500 m, with a summit platform 35 by 70 kilometres wide. The Mid-Pacific Mountains lie west of Hawaii and northeast of the Marshall Islands, but at the time of their formation were located in the Southern Hemisphere.

Vlinder Guyot

Vlinder Guyot is a guyot in the Western Pacific Ocean. It rises to a depth of 1,500 metres (4,900 ft) and has a flat top covering an area of 40 by 50 kilometres. On top of this flat top lie some volcanic cones, one of which rises to a depth of 551 metres (1,808 ft) below sea level. Vlinder Guyot has noticeable rift zones, including an older and lower volcano to the northwest and Oma Vlinder seamount south.

References

  1. 1 2 Guyot Encyclopædia Britannica Online, 2010. Retrieved January 14, 2010.
  2. 1 2 Bryson, Bill. "A Short History of Nearly Everything". New York: Broadway, 2003. p. 178
  3. Guyot, Arnold in A Princeton Companion
  4. "Guyot". www.utdallas.edu. Retrieved 15 January 2019.
  5. Seamounts are made by extrusion of lavas piped upward in stages from sources within the Earth's mantle to vents on the seafloor. Seamounts provide data on movements of tectonic plates on which they ride, and on the rheology of the underlying lithosphere. The trend of a seamount chain traces the direction of motion of the lithospheric plate over a more or less fixed heat source in the underlying asthenosphere part of the Earth's mantle.
  6. Hillier, J. K. (2007). "Pacific seamount volcanism in space and time". Geophysical Journal International. 168 (2): 877–889. Bibcode:2007GeoJI.168..877H. doi:10.1111/j.1365-246X.2006.03250.x.
  7. 1 2 "Seamount and guyot". Access Science. doi:10.1036/1097-8542.611100 . Retrieved 2 February 2016.
  8. "Great Meteor Tablemount (volcanic mountain, Atlantic Ocean) – Britannica Online Encyclopedia". britannica.com. Retrieved 15 January 2019.
  9. "Answers - The Most Trusted Place for Answering Life's Questions". Answers.com. Retrieved 15 January 2019.
  10. Harris, P.T.; Macmillan-Lawler, M.; Rupp, J.; Baker, E.K. (2014). "Geomorphology of the oceans". Marine Geology. 352: 4–24. Bibcode:2014MGeol.352....4H. doi:10.1016/j.margeo.2014.01.011.
  11. . doi:10.1002/2015GC0059310 (inactive 2019-02-20).Missing or empty |title= (help)
  12. Sahfos [ permanent dead link ]