Английская Википедия:Arago hotspot

Материал из Онлайн справочника
Перейти к навигацииПерейти к поиску

Шаблон:Short description Шаблон:Good article

Файл:Hotspots-more.jpg
Map of the hotspots on Earth. Arago is #59
Файл:HotspotHighway.jpg
The Argo hotspot is a component of the South Pacific Ocean Hotspot highwayШаблон:Sfn

Arago hotspot (also known as the Rurutu hotspot, Young Rurutu hotspot or Atiu hotspot) is a hotspot in the Pacific Ocean, presently located below the Arago seamount close to the island of Rurutu, French Polynesia.

Arago is part of a family of hotspots in the southern Pacific, which include the Society hotspot and the Macdonald hotspot among others. These are structures beneath Earth's crust which generate volcanoes and which are in part formed by mantle plumes, although Arago itself might have a shallower origin. As the Pacific plate moves over the hotspots, new volcanoes form and old volcanoes are carried away; sometimes an older volcano is carried over the hotspot and is then uplifted as happened with Rurutu.

The Arago hotspot is responsible for the formation of Arago seamount and uplift on Rurutu; however reconstructions of the past positions of tectonic plates and geochemistry suggest that other islands and seamounts were constructed by the Arago hotspot during the past 120 million years. These potentially include the Wake Seamounts, the Ratak Chain of the Marshall Islands, numerous seamounts northwest of the Marshall Islands, Tuvalu, Gilbert Islands as well as part of the Austral Islands and Cook Islands.

Name

The hotspot is named after the Arago seamount Шаблон:Convert southeast of Rurutu. The seamount is named after the French Navy ship Arago, which discovered the seamount in 1993.Шаблон:Sfn The ship itself is named after astronomer François Arago.[1] Polynesians knew of the existence of the shallow (Шаблон:Convert beneath sea level) seamount and named it Tinomana.Шаблон:Sfn Before the link to Arago seamount was discovered, the hotspot was also known as "Rurutu hotspot",Шаблон:SfnШаблон:Sfn a name sometimes still used,Шаблон:Sfn which is a name also used for an older volcanic chain that starts at RaivavaeШаблон:Sfn or President Thiers Bank.Шаблон:Sfn Other names are "Young Rurutu"Шаблон:Sfn and "Atiu trend";Шаблон:SfnШаблон:Sfn "Old Rurutu" refers to the Macdonald hotspot.[2]

Geography and geology

Шаблон:OSM Location map

Файл:French Polynesia relief map.svg
The islands in the southern Pacific Ocean

The southern Pacific Ocean is the site of the South Pacific Superswell, an area where the ocean is anomalously shallow (by about Шаблон:Convert)Шаблон:SfnШаблон:Sfn and which covers an area of about Шаблон:Convert.Шаблон:Sfn Underneath this superswell a large mantle plume might give rise to secondary plumes which in turn form the surface hotspots.Шаблон:Sfn Hotspots in the region are the Macdonald hotspot, Marquesas hotspot, Pitcairn hotspot and Society hotspot;Шаблон:Sfn of which the first and the last appear to be rooted deep in the mantle.Шаблон:Sfn The nature of the volcanism in the area is not completely understood.Шаблон:Sfn

Arago Seamount is part of the volcanic chain that forms the Austral Islands and Cook Islands. The Шаблон:Convert long chain consists of two separate trends that form two atolls and eleven islands; of these systems one (Macdonald seamount) is a still active volcano.Шаблон:Sfn The ages of these islands follow an approximate age progression typical of a hotspot volcano but the occurrence of younger ages on Aitutaki and Rurutu and the chemistry of these younger rocks indicated that there must be more than one hotspot involved.Шаблон:Sfn Recent models envisage the presence of a number of separate hotspot tracks in what has been dubbed a "hotspot highway",Шаблон:Sfn, first named as such in 2010,Шаблон:Snf fed by plumes Шаблон:Convert apart.Шаблон:Sfn Further, some hotspots such as the Hawaii hotspot show evidence of movement but the Arago hotspot appears to be static.Шаблон:Sfn

The Arago and other hotspots probably are not deep mantle plumes but rather more shallow structures that are also influenced by the lithosphere;Шаблон:Sfn in the case of the Arago hotspot the absence of an oceanic plateau that could have been formed by the head of the mantle plume supports such a shallow origin.Шаблон:Sfn The upper mantle might be the source of the Arago hotspot.Шаблон:Sfn Data on the presence of seismic velocity anomalies and whether they are positive (higher) or negative (lower) beneath Arago are contradictory.Шаблон:Sfn Seismic imaging published in 2009 indicates only a slight seismic velocity anomaly shallower than Шаблон:Convert,Шаблон:Sfn with no indication of a deep mantle root.Шаблон:Sfn More recent research however has endorsed a deep mantle origin for the Arago hotspot.Шаблон:Sfn Presently, Arago and the Macdonald hotspot are the two active hotspots of the Austral Islands,[3] but a hotspot that formed Rarotonga may also still be active; additional hotspots in the area are Tubuai, Taukina and Ngatemato.Шаблон:Sfn Arago is a long lived hotspot that could be as much as 140 million years old.Шаблон:Sfn

Arago Seamount

The eponymous Arago Seamount is a composite volcano with three rift zones, similar to Rurutu.Шаблон:Sfn The seamount was formed by three volcanoes with one overlapping the other two; potassium-argon dating on Arago has yielded ages of 230,000 ± 4,000 before present and an imprecise age of 0 years before present.Шаблон:Sfn There is some evidence of submarine landslide activity, a typical occurrence on ocean volcanoes,[3] with one landslide scar each on the northern, eastern and western flank.[4] This seamount is considered to be the present location of the hotspot, given its young age;Шаблон:Sfn however, unlike Macdonald, Arago Seamount has no recorded historical eruptions.Шаблон:Sfn

Hotspots other than the Arago hotspot may have contributed to the growth of the Arago Seamount; a hotspot associated with Raivavae and potentially the President Thiers Bank has been associated through isotope analysis with 8.2 million year old samples taken from Arago Seamount.Шаблон:Sfn Other volcanoes in the region also show evidence that they were built by more than one hotspot; this might indicate that their formation is controlled by lithospheric features.Шаблон:Sfn

Other islands and seamounts

Файл:Pacific Basin Island Geography Hotspots.jpg
Hotspot provinces in the Pacific Ocean; Arago belongs to the "Macdonald" province

As the Pacific Plate drifted over the hotspot several volcanoes were formed on the hotspot where weaknesses in the crust allowed the penetration of magma, and were subsequently carried away,Шаблон:SfnШаблон:Sfn at a rate of about Шаблон:Convert.Шаблон:Sfn Isotope ratios of lead in the volcanic rocks tie the younger volcanics of Rurutu to the Arago hotspot,Шаблон:Sfn the ratio in this case is characterized by high radiogenic lead isotope composition ("HIMU").Шаблон:Sfn Some volcanic material from the Arago hotspot may have been recycled in the mantle and mixed into the magmas erupted in the northeastern Lau basin;[5] rocks shed from seamounts created by the Arago hotspot may have been subducted in the Tonga trench which is close to the reconstructed path of the Arago hotspot and then erupted onto the Lau basin.Шаблон:Sfn HIMU xenoliths have been found in Tubuai just ahead of Arago Seamount as well.Шаблон:Sfn

Rurutu already existed before the interaction with the Arago hotspot, having been formed by an older volcanic episode; when it moved over the Arago hotspot a volcanic episode occurred and emplaced lava flows that are formed by basanite and hawaiite. Also, the island and surrounding coral reef were uplifted,Шаблон:Sfn and these uplifted coral reefs (known as makatea) caught the attention of early geologists, who were speculating as to what might have lifted the reefs out of the sea already in 1840.Шаблон:Sfn Other uplifted atolls occur northwest from Rurutu and may have formed in the same way when they passed over the Arago hotspot.Шаблон:Sfn

Шаблон:GeoGroup The following volcanics are at least tentatively attributed to the Arago hotspot:

The oldest volcanic structures potentially formed by the Arago hotspot are 120 million years old. If their attribution is correct, the Arago hotspot may be the oldest still active hotspot in the Pacific Ocean, ahead of the Hawaii hotspot and the Louisville hotspot.[6] A contrasting viewpoint believes that Arago is a short-lived hotspot with few dated volcanoes along its predicted path.Шаблон:Sfn Assuming the first is the case, it is possible to fit Pacific Plate movements over the last 80 million years to the widely separate postulated tracks of this hotspot, the Louisville hotspot and the Hawaii hotspot very well.[12]

The island of Tubuai is located ahead of the hotspot, and the island will be transported over it in a few million years. As with Rurutu, this interaction will lead to uplift in Tubuai and possibly to renewed volcanism.Шаблон:Sfn

References

Шаблон:Reflist

Sources

Шаблон:Refbegin

Шаблон:Refend

External links

Шаблон:Hotspots Шаблон:Coord

Партнерские ресурсы
Криптовалюты
Магазины
Хостинг
Разное

  1. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Arago не указан текст
  2. ↑ Ошибка цитирования Неверный тег <ref>; для сносок KonterFinlayson2019 не указан текст
  3. ↑ 3,0 3,1 Ошибка цитирования Неверный тег <ref>; для сносок ClouardBonneville2003 не указан текст
  4. ↑ Ошибка цитирования Неверный тег <ref>; для сносок ClouardBonneville2004 не указан текст
  5. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Price2014 не указан текст
  6. ↑ 6,0 6,1 Ошибка цитирования Неверный тег <ref>; для сносок Koppers2013 не указан текст
  7. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Finlayson2016 не указан текст
  8. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Konter2019 не указан текст
  9. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Finlayson2014 не указан текст
  10. ↑ Ошибка цитирования Неверный тег <ref>; для сносок YanMilan2021 не указан текст
  11. ↑ Ошибка цитирования Неверный тег <ref>; для сносок FrancoAbbott1999 не указан текст
  12. ↑ Ошибка цитирования Неверный тег <ref>; для сносок GaastraGordon2022 не указан текст
Источник — http://wikihandbk.com/ruwiki/index.php?title=Английская_Википедия:Arago_hotspot&oldid=13221896