The Tristan hotspot is a volcanic hotspot which is responsible for the volcanic activity which forms the volcanoes in the southern Atlantic Ocean. It is thought to have formed the island of Tristan da Cunha and the Walvis Ridge on the African Plate. [1]
It is also believed to be closely connected with the Paraná and Etendeka flood basalt provinces, which formed over the hotspot during the opening of the South Atlantic Ocean. [2]
The Tristan and Gough hotspots are widely spaced end-members of the volcanic system that generated the Walvis Ridge on the African plate and the Rio Grande Rise on the South American plate beginning at 129 to 133 Ma when the Paraná and Etendeka traps formed. Whether or not Tristan and Gough represent two distinct volcanic centers is still debated. [3]
Fairhead & Wilson 2005 argued that the Walvis Ridge is not the product of a deep mantle plume or the Tristan hotspot, but that changes in the internal stress in the spreading African and South American plates trigger changes in the magmatic processes in the Mid-Atlantic Ridge. The Walvis Ridge should then have developed as a result of these periodic stress releases along the Mid-Atlantic Ridge. [4]
O'Connor et al. 2012 found that the hotspot trails in the eastern South Atlantic (Tristan, Gough, Discovery, Shona, and possibly Bouvet) started forming synchronously 44 to 41 Ma. Older seamounts east of these hotspot trails formed at the edge of the African swell where the oceanic crust was spreading apart and are not the product of hotspot volcanism. The Tristan-Gough trail switched from forming a series of aseismic ridges to a broader line of guyots and smaller volcanic ridges at about the same time. [5]
The hotspots of the eastern South Atlantic formed along the plume generation zones of the African large low seismic velocity province (LLSVP). LLSVPs are dense and stable structures, and most of the plumes, kimberlites, and large igneous provinces (LIPs) on Earth can be rotated back to the plume generation zones. All major African LIPs (Karoo, Paraná-Etendeka, and Agulhas) formed at the plume generation zones of the African LLSVP but 132 to 100 Ma the Tristan-Gough hotspot was the only hotspot located at a spreading boundary and therefore the only African hotspot that started to form a volcanic trail. [5]
Based on molecular estimates, Arnason et al. 2000 found that the Homo–Pan divergence occurred 13 to 10.5 Ma (in contrast to earlier estimates that suggested around 5 Ma). [6] Arnason et al. also estimated the Platyrrhini – Catarrhini divergence to have occurred around 70 Ma and found that the latter evolved in South America before their dispersal into Africa. Arnason et al. hypothesised that the Rio Grande–Walvis Ridge system was exposed above sea level and formed a chain of islands across the South Atlantic during the Maastrichtian and Palaeocene 70 to 65 Ma allowing the primates to disperse across the ocean. [7] Other researchers dismiss the hypothesis of Arnason et al. instead favouring a less spectacular rafting event. [8]
Other hints of transoceanic island hopping in the fossil record is Lavocatavis , a flightless terror bird found in Eocene layers in Algeria, the only one found outside South America. [9]
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries.
In geology, hotspots are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of tectonic plate boundaries, and so hotspots may create a chain of volcanoes as the plates move above them.
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.
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.
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.
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, and 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.
The term "mesoplates" has been applied in two different contexts within geology and geophysics. The first is applicable to much of the Earth's mantle, and the second to distinct layering within the Earth's crust.
The Paraná-Etendeka Large Igneous Province (PE-LIP) (or Paraná and Etendeka Plateau; or Paraná and Etendeka Province) comprise a large igneous province that includes both the main Paraná traps (in Paraná Basin, a South American geological basin) as well as the smaller severed portions of the flood basalts at the Etendeka traps (in northwest Namibia and southwest Angola). The original basalt flows occurred 136 to 132 million years ago. The province had a post-flow surface area of 1,000,000 square kilometres (390,000 sq mi) and an original volume projected to be in excess of 2.3 x 106 km³.
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 and South American plates. The volcanism took place between 139 and 69 million years ago, 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 x 106 km³. It has been linked to the Galápagos hotspot.
The New England hotspot, also referred to as the Great Meteor hotspot and sometimes the Monteregian hotspot, is a volcanic hotspot in the North Atlantic Ocean. It created the Monteregian Hills intrusions in Montreal and Montérégie, the White Mountains intrusions in New Hampshire, the New England and Corner Rise seamounts off the coast of North America, and the Seewarte Seamounts east of the Mid-Atlantic Ridge on the African Plate, the latter of which include its most recent eruptive center, the Great Meteor Seamount. The New England, Great Meteor, or Monteregian hotspot track has been used to estimate the movement of the North American Plate away from the African Plate from the early Cretaceous period to the present using the fixed hotspot reference frame.
The Terceira Rift is a geological rift located amidst the Azores islands in the Atlantic Ocean. It runs between the Azores Triple Junction to the west and the Azores–Gibraltar Transform Fault to the southeast. It separates the Eurasian Plate to the north from the African Plate to the south. The Terceira Rift is named for Terceira Island through which it passes. It crosses Terceira Island as a prominent ESE-WNW fissure zone.
The Southwest Indian Ridge (SWIR) is a mid-ocean ridge located along the floors of the south-west Indian Ocean and south-east Atlantic Ocean. A divergent tectonic plate boundary separating the Somali Plate to the north from the Antarctic Plate to the south, the SWIR is characterised by ultra-slow spreading rates (only exceeding those of the Gakkel Ridge in the Arctic) combined with a fast lengthening of its axis between the two flanking triple junctions, Rodrigues (20°30′S70°00′E) in the Indian Ocean and Bouvet (54°17′S1°5′W) in the Atlantic Ocean.
The Walvis Ridge is an aseismic ocean ridge in the southern Atlantic Ocean. More than 3,000 km (1,900 mi) in length, it extends from the Mid-Atlantic Ridge, near Tristan da Cunha and the Gough Islands, to the African coast. The Walvis Ridge is one of few examples of a hotspot seamount chain that links a flood basalt province to an active hotspot. It is also considered one of the most important hotspot tracks because the Tristan Hotspot is one of few primary or deep mantle hotspots.
The Shona or Meteor hotspot is a volcanic hotspot located in the southern Atlantic Ocean. Its zig-zag-shaped hotspot track, a chain of seamounts and ridges, stretches from its current location at or near the southern end of the Mid-Atlantic Ridge to South Africa.
The Rio Grande Rise, also called the Rio Grande Elevation or Bromley Plateau, is an aseismic ocean ridge in the southern Atlantic Ocean off the coast of Brazil. Together with the Walvis Ridge off Africa, the Rio Grande Rise forms a V-shaped structure of mirrored hotspot tracks or seamount chains across the northern South Atlantic. In 2013, Brazilian scientists announced that they found granite boulders on the Rio Grande Rise and speculated that it could be the remains of a submerged continent, which they called the "Brazilian Atlantis". Other researchers, however, noted that such boulders can end-up on the ocean floor by less speculative means.
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.
Noronha hotspot is a hypothesized hotspot in the Atlantic Ocean. It has been proposed as the candidate source for volcanism in the Fernando de Noronha archipelago of Brazil, as well as of other volcanoes also in Brazil and even the Bahamas and the Central Atlantic Magmatic Province.
The Rarotonga hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot is claimed to be responsible for the formation of Rarotonga and some volcanics of Aitutaki but an alternative explanation for these islands most recent volcanics has not been ruled out. Recently alternatives to hotspot activity have been offered for several other intra-plate volcanoes that may have been associated with the Rarotonga hotspot hypothesis.
The Equatorial Atlantic Magmatic Province (EQUAMP) is a Cretaceous large igneous province (LIP) in South America covering 700,000 km2 (270,000 sq mi). The break-up of the supercontinent Gondwana resulted in a series of large volcanic eruptions, but EQUAMP is the only Gondwanan LIP composed exclusively of intrusive rock, making it a Large Plutonic Province (LPP).
Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial.