Oceanic plateau

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Map showing the location of oceanic plateaus (in green) in the Australia-New Zealand region of the South Pacific Map showing the location of oceanic plateaus (in green) in the Australia-New Zealand region of the South Pacific.svg
Map showing the location of oceanic plateaus (in green) in the Australia-New Zealand region of the South Pacific

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. [1]

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There are 184 oceanic plateaus in the world, covering an area of 18,486,600 km2 (7,137,700 sq mi) or about 5.11% of the oceans. [2] The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map).

Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example the Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges. [3] Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the United States.

In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources. These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As a consequence, they tend to "dock" to continental margins and be preserved as accreted terranes. Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had a dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean. [4]

Role in crust–mantle recycling

Geologists believe that igneous oceanic plateaus may well represent a stage in the development of continental crust as they are generally less dense than oceanic crust while still being denser than normal continental crust.

Density differences in crustal material largely arise from different ratios of various elements, especially silicon. Continental crust has the highest amount of silicon (such rock is called felsic). Oceanic crust has a smaller amount of silicon (mafic rock). Igneous oceanic plateaus have a ratio intermediate between continental and oceanic crust, although they are more mafic than felsic.

However, when a plate carrying oceanic crust subducts under a plate carrying an igneous oceanic plateau, the volcanism which erupts on the plateau as the oceanic crust heats up on its descent into the mantle erupts material which is more felsic than the material which makes up the plateau. This represents a step toward creating crust which is increasingly continental in character, being less dense and more buoyant. If an igneous oceanic plateau is subducted underneath another one, or under existing continental crust, the eruptions produced thereby produce material that is yet more felsic, and so on through geologic time.

List of oceanic plateaus

Global distribution of oceanic plateaus [5]
OceanArea
(km2)		Plateau
area (%)		Number of
plateaus		Average plateau
area (km2)
Arctic Ocean1,193,7409.191299,480
Indian Ocean5,036,8707.0637136,130
North Atlantic Ocean1,628,3603.643645,230
North Pacific Ocean1,856,7902.263356,270
South Atlantic Ocean1,220,2303.029135,580
South Pacific Ocean7,054,8008.0950141,100
Southern Ocean495,8302.441241,320
World Ocean18,486,6105.11184100,470
The Rockall Plateau in the North Atlantic is underlain by continental crust. It rifted from Greenland during the opening of the North Atlantic. Rockall Plateau and Trough, NE Atlantic.png
The Rockall Plateau in the North Atlantic is underlain by continental crust. It rifted from Greenland during the opening of the North Atlantic.

Continental oceanic plateaus

Igneous oceanic plateaus

See also

Related Research Articles

<span class="mw-page-title-main">Flood basalt</span> Very large volume eruption of basalt lava

A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the Earth via a mantle plume. Flood basalt provinces such as the Deccan Traps of India are often called traps, after the Swedish word trappa, due to the characteristic stairstep geomorphology of many associated landscapes.

<span class="mw-page-title-main">Large igneous province</span> Huge regional accumulation of igneous rocks

A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.

<span class="mw-page-title-main">Earth's crust</span> Earths outer shell of rock

Earth's crust is its thick outer shell of rock, referring to less than one percent of the planet's radius and volume. It is the top component of the lithosphere, a solidified division of Earth's layers that includes the crust and the upper part of the mantle. The lithosphere is broken into tectonic plates whose motion allows heat to escape the interior of Earth into space.

<span class="mw-page-title-main">Kerguelen Plateau</span> Oceanic plateau in the southern Indian Ocean

The Kerguelen Plateau, also known as the Kerguelen–Heard Plateau, is an oceanic plateau and large igneous province (LIP) located on the Antarctic Plate, in the southern Indian Ocean. It is about 3,000 km (1,900 mi) to the southwest of Australia and is nearly three times the size of California. The plateau extends for more than 2,200 km (1,400 mi) in a northwest–southeast direction and lies in deep water.

<span class="mw-page-title-main">Early Cretaceous</span> First epoch of the Cretaceous Period

The Early Cretaceous or the Lower Cretaceous is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.

<span class="mw-page-title-main">Naturaliste Plateau</span> Submarine plateau in Indian Ocean

The Naturaliste Plateau is one of several large submarine plateaus extending from Western Australia into the Indian Ocean. It is a rectilinear plateau that covers an area of 90,000 square kilometres. Its width is about 400 kilometres (250 mi) east-west and 250 km (160 mi) north-south. The water depths are from 1500 to 5000 metres.

The Ontong Java Plateau (OJP) is a massive oceanic plateau located in the southwestern Pacific Ocean, north of the Solomon Islands. The OJP was formed around 116 million years ago (Ma), with a much smaller volcanic event around 90 Ma. Two other southwestern Pacific plateaus, Manihiki and Hikurangi, now separated from the OJP by Cretaceous oceanic basins, are of similar age and composition and probably formed as a single plateau and a contiguous large igneous province together with the OJP. When eruption of lava had finished, the Ontong Java–Manihiki–Hikurangi plateau covered 1% of Earth's surface and represented a volume of 80 million km3 (19 million cu mi) of basaltic magma. This "Ontong Java event", first proposed in 1991, represents the largest volcanic event of the past 200 million years, with a magma eruption rate estimated at up to 22 km3 (5.3 cu mi) per year over 3 million years, several times larger than the Deccan Traps. The smooth surface of the OJP is punctuated by seamounts such as the Ontong Java Atoll, one of the largest atolls in the world.

<span class="mw-page-title-main">Kerguelen hotspot</span> Hotspot under the Indian Ocean

The Kerguelen hotspot is a volcanic hotspot at the Kerguelen Plateau in the Southern Indian Ocean. The Kerguelen hotspot has produced basaltic lava for about 130 million years and has also produced the Kerguelen Islands, Naturaliste Plateau, Heard Island, the McDonald Islands, the Comei large igneous province in south Tibet, and the Rajmahal Traps. One of the associated features, the Ninety East Ridge, is distinguished by its over 5,000 km (3,100 mi) length, being the longest linear tectonic feature on Earth. The total volume of magma erupted in 130 million years with associated features has been estimated to be about 25,000,000 km3 (6,000,000 cu mi). However, as well as large igneous provinces and seamounts the hotspot has interacted with other seafloor spreading features, so this volume figure has some uncertainty.

<span class="mw-page-title-main">Caribbean large igneous province</span> Accumulation of igneous rocks

The Caribbean large igneous province (CLIP) consists of a major flood basalt, which created this large igneous province (LIP). It is the source of the current large eastern Pacific oceanic plateau, of which the Caribbean-Colombian oceanic plateau is the tectonized remnant. The deeper levels of the plateau have been exposed on its margins at the North American and South American plates. The volcanism took place between 139 and 69 million years ago (Ma), with the majority of activity appearing to lie between 95 and 88 Ma. The plateau volume has been estimated as on the order of 4 million km3 (0.96 million cu mi). It has been linked to the Galápagos hotspot.

Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin.

<span class="mw-page-title-main">Southeast Indian Ridge</span> Mid-ocean ridge in the southern Indian Ocean

The Southeast Indian Ridge (SEIR) is a mid-ocean ridge in the southern Indian Ocean. A divergent tectonic plate boundary stretching almost 6,000 km (3,700 mi) between the Rodrigues triple junction in the Indian Ocean and the Macquarie triple junction in the Pacific Ocean, the SEIR forms the plate boundary between the Australian and Antarctic plates since the Oligocene (anomaly 13).

Volcanic passive margins (VPM) and non-volcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on Earth as the result of the formation of ocean basins via continental rifting. Initiation of igneous processes associated with volcanic passive margins occurs before and/or during the rifting process depending on the cause of rifting. There are two accepted models for VPM formation: hotspots/mantle plumes and slab pull. Both result in large, quick lava flows over a relatively short period of geologic time. VPM's progress further as cooling and subsidence begins as the margins give way to formation of normal oceanic crust from the widening rifts.

<span class="mw-page-title-main">Igneous rock</span> Rock formed through the cooling and solidification of magma or lava

Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.

A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.

<span class="mw-page-title-main">Agulhas Plateau</span>

The Agulhas Plateau is an oceanic plateau located in the south-western Indian Ocean about 500 km (310 mi) south of South Africa. It is a remainder of a large igneous province (LIP), the Southeast African LIP, that formed 140 to 95 million years ago (Ma) at or near the triple junction where Gondwana broke-up into Antarctica, South America, and Africa. The plateau formed 100 to 94 Ma together with Northeast Georgia Rise and Maud Rise when the region passed over the Bouvet hotspot.

<span class="mw-page-title-main">Agulhas Passage</span> Abyssal channel south of South Africa between the Agulhas Bank and Agulhas Plateau

The Agulhas Passage is an abyssal channel located south of South Africa between the Agulhas Bank and Agulhas Plateau. About 50 km (31 mi) wide, it connects the Natal Valley and Transkei Basin in the north to the Agulhas Basin in the south and is the only near-shore connection between the south-western Indian Ocean and South Atlantic Ocean.

<span class="mw-page-title-main">Broken Ridge</span> Oceanic plateau in the Indian Ocean

The Broken Ridge or Broken Plateau is an oceanic plateau in the south-eastern Indian Ocean. The Broken Ridge once formed a large igneous province (LIP) together with the Kerguelen Plateau. When Australia and Antarctica started to separate, the Broken Ridge and the Kerguelen Plateau got separated by the Southeast Indian Ridge. Alkalic basalt from the Broken Ridge has been dated to 95 Ma.

The Discovery Seamounts are a chain of seamounts in the Southern Atlantic Ocean, including Discovery Seamount. The seamounts are 850 kilometres (530 mi) east of Gough Island and once formed islands. Various volcanic rocks as well as glacial dropstones and sediments have been dredged from the Discovery Seamounts.

<span class="mw-page-title-main">Dharwar Craton</span> Part of the Indian Shield in south India

The Dharwar Craton is an Archean continental crust craton formed between 3.6-2.5 billion years ago (Ga), which is located in southern India and considered the oldest part of the Indian peninsula.

References

Notes

  1. ↑ IHO 2013 , pp. 2–12
  2. ↑ Harris et al. 2014 , Plateaus (Supplementary Table 20), p. 16
  3. ↑ Mooney, Laske & Masters 1998 , Anomalous Crust: Oceanic Plateaus, Hotspots, and Rifts, pp. 754–755
  4. ↑ Kerr 2013 , p. 632
  5. ↑ Harris et al. 2014 , Supplementary table 20
  6. 1 2 Boldreel & Andersen 1994 , p. 163
  7. ↑ Uenzelmann-Neben et al. 1999
  8. ↑ Hildenbrand, Anthony; Weis, Dominique; Madureira, Pedro; Margues, Fernando Ornelas (2014). "Recent plate re-organization at the Azores Triple Junction: Evidence from combined geochemical and geochronological data on Faial, S. Jorge and Terceira volcanic islands". Lithos . 210: 27. Bibcode:2014Litho.210...27H. doi:10.1016/j.lithos.2014.09.009. hdl: 10174/13522 . ISSN   0024-4937.
  9. ↑ Lee, E.Y.; Wolfgring, Erik; Tejada, M.L.G.; et al. (2020). "Early Cretaceous subsidence of the Naturaliste Plateau defined by a new record of volcaniclastic-rich sequence at IODP Site U1513" (PDF). Gondwana Research . 82: 1–11. Bibcode:2020GondR..82....1L. doi:10.1016/j.gr.2019.12.007. hdl:2434/707329. S2CID   213041290.

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