The St. Helena hotspot is a volcanic hotspot located in the southern Atlantic Ocean. It is responsible for the island of St. Helena and the St. Helena Seamount chain. It is one of the oldest known hotspots on Earth, which began to produce basaltic lava about 145 million years ago. [1]
Saint Helena is a British overseas territory located in the South Atlantic Ocean. It is a remote volcanic tropical island 1,950 km (1,210 mi) west of the coast of south-western Africa, and 4,000 km (2,500 mi) east of Rio de Janeiro in South America. It is one of three constituent parts of the British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha.
The Samoan archipelago is a chain of 16 islands and numerous seamounts covering 3,123 km2 (1,206 sq mi) in the central South Pacific, south of the equator, about halfway between Hawaii and New Zealand, forming part of Polynesia and of the wider region of Oceania. The islands are Savaiʻi, Upolu, Tutuila, ’Uvea, Taʻū, Ofu, Olosega, Apolima, Manono, Nuʻutele, Niulakita, Nuʻulua, Namua, Fanuatapu, Rose Atoll, Nu'ulopa, as well as the submerged Vailuluʻu, Pasco banks, and Alexa Bank.
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 Cobb hotspot is a marine volcanic hotspot at, which is 460 km (290 mi) west of Oregon and Washington, North America, in the Pacific Ocean. Over geologic time, the Earth's surface has migrated with respect to the hotspot through plate tectonics, creating the Cobb–Eickelberg Seamount chain. The hotspot is currently collocated with the Juan de Fuca Ridge.
The Hawaiʻi hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the best known and intensively studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian–Emperor seamount chain, a 6,200-kilometer (3,900 mi) mostly undersea volcanic mountain range. Four of these volcanoes are active, two are dormant; more than 123 are extinct, most now preserved as atolls or seamounts. The chain extends from south of the island of Hawaiʻi to the edge of the Aleutian Trench, near the eastern coast of Russia.
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 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).
The Ninety East Ridge is a mid-ocean ridge on the Indian Ocean floor named for its near-parallel strike along the 90th meridian at the center of the Eastern Hemisphere. It is approximately 5,000 kilometres (3,100 mi) in length and can be traced topographically from the Bay of Bengal southward towards the Southeast Indian Ridge (SEIR), though the feature continues to the north where it is hidden beneath the sediments of the Bengal Fan. The ridge extends between latitudes 31°S and 9°N and has an average width of 200 km.
The St. Helena Seamount chain, also known as the St. Helena Seamounts, is an underwater chain of seamounts in the southern Atlantic Ocean. The chain has been formed by the movement of the African Plate over the Saint Helena hotspot.
Mugearite is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase.
The Samoa hotspot is a volcanic hotspot located in the south Pacific Ocean. The hotspot model describes a hot upwelling plume of magma through the Earth's crust as an explanation of how volcanic islands are formed. The hotspot idea came from J. Tuzo Wilson in 1963 based on the Hawaiian Islands volcanic chain.
Saint Helena, Ascension and Tristan da Cunha is a British Overseas Territory located in the South Atlantic and consisting of the island of Saint Helena, Ascension Island, and the archipelago of Tristan da Cunha. Its name was Saint Helena and Dependencies until 1 September 2009, when a new constitution came into force giving the three islands equal status as three territories, with a grouping under the Crown.
This timeline of volcanism on Earth includes a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic explosivity index (VEI) or equivalent sulfur dioxide emission during the Quaternary period. Other volcanic eruptions are also listed.
The Trindade hotspot is a working hypothesis supposing that the submarine volcanic chain Vitória-Trindade, off the eastern coast of Brazil in the southern Atlantic Ocean, is a volcanic hotspot chain. It was considered that the supposed hot-spot should be responsible for the creation of the east-west trending Vitória-Trindade seamount chain, which includes the Trindade and Martim Vaz archipelago at its easternmost end. Trindade, a small island in the archipelago, is the hotspot's most recent eruptive center.
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.
Arago hotspot is a hotspot in the Pacific Ocean, presently located below the Arago seamount close to the island of Rurutu, French Polynesia.
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 geology of Saint Helena resulted from the long-running volcanic activity of the Saint Helena hotspot. Most of the island was formed beginning 14 million years ago. Volcanism on the island ceased seven million years ago, leading to long-running erosion and the formation of deep, v-shaped valleys along with steep coastal cliffs. Some geochemists have observed significant trace element variations between South Atlantic islands and proposed that deep-ocean sediments may have mixed into the magma which formed Saint Helena.
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