Azores Triple Junction

The spreading rate along the MAR does not change abruptly at the ATJ, instead decreasing from 22.9±0.1 mm/yr at 40°N to 19.8±0.2 mm/yr at 38°N. This means the ATJ is not a simple triple junction where three tectonic plates meet at a point. The transitional range of spreading rates instead indicates the presence of a microplate, commonly referred to as the Azores microplate, although the observed behaviour can also be explained in terms of a diffuse boundary.[1] Its northern boundary intersects the MAR between 39.4°N and 40.0°N and its southern between 38.2°N and 38.5°N. The microplate moves about 2 mm/yr east-northeast along its Nubian boundary.[2]

Azorestriple3d
The Azores Triple Junction

Coordinates: 39°26′N 29°50′W / 39.44°N 29.83°W The Azores Triple Junction (ATJ) is a geologic triple junction where the boundaries of three tectonic plates intersect: the North American Plate, the Eurasian Plate and the African Plate. This triple junction is located along the Mid-Atlantic Ridge (MAR) amidst the Azores islands, nearly due west of the Strait of Gibraltar. It is classed as a R-R-R triple junction of the T type (for its shape), as it is an intersection of the Mid-Atlantic Ridge running north-south and the Terceira Rift which runs east-southeast.

References

Notes
  1. ^ F.O. Marques, J.C. Catalão, C.DeMets, A.C.G. Costa, A. Hildenbrand (2013). "GPS and tectonic evidence for a diffuse plate boundary at the Azores Triple Junction" (PDF). Earth and Planetary Science Letters. 381: 177–187.CS1 maint: Multiple names: authors list (link)
  2. ^ DeMets, Gordon & Argus 2010, The Azores microplate, pp. 24–25
Sources
Aden-Owen-Carlsberg Triple Junction

The Aden-Owen-Carlsberg Triple Junction (AOC), also known as the Arabia–India–Somalia Triple Junction, is a triple junction that connects the Aden Ridge, Owen Fracture Zone, and Carlsberg Ridge in the northwest Indian Ocean.

It has been described as one of only three RRF (ridge-ridge-fault) triple junctions on Earth, besides the Azores Triple Junction and Chile Triple Junction. However, because the fault arm of such unstable triple junctions tend to evolve into a spreading centre, all three cases have quickly evolved into stable RRR triple junctions.Since a reorganisation of the involved tectonic plates c. 10 Ma the AOC moves in discrete steps westward along the Aden Ridge. West of the southern termination of the Owen fracture Zone, the Beautemps-Beaupré Basin, a new plate boundary develops and the basin will be transferred from the Arabian Plate to the Indian Plate in a near future.The Carlsberg Ridge was opened between the Seychelles and India in the Early Tertiary and has since undergone three stages of spreading. A first, fast stage 61 to 51 Ma with a 6 cm/year (2.4 in/year) half-rate spreading; a second 39 to 23 Ma ultra-slow (0.6 cm/year (0.24 in/year)) stage during the India-Eurasia collision; followed by the present slow (1.2 cm/year (0.47 in/year)) spreading which reaches 2.2 ± 0.1 cm/year (0.866 ± 0.039 in/year) in its northern end. This latest stage was initiated by the opening of the Gulf of Aden during which the Aden Ridge began to quickly propagate westward at a rate of 200 km (120 mi)/Ma.The Owen Fracture Zone, together with the Dalrymple Trough in its northern end, is a transform fault along which spreading between the Arabian and Indian Plates at the Carlsberg Ridge becomes the subduction of the Himalayan orogeny. The Owen Fracture Zone passes east of the Owen Ridge which was uplifted during the opening of the eastern Gulf of Aden in the Early Miocene. North of the Aden-Owen-Carlsberg Triple Junction the Owen Fracture Zone is quiet for 250 km (160 mi) but right-lateral slip along its active segments indicates that Arabia is moving northward faster than India.The relative motion between the Nubian and Somalian plates before 3.2 Ma is difficult to determine since the movement in the Southwest Indian Ridge is extremely slow. Analysing the Aden-Owen-Carlsberg Triple Junction, however, geologists have been able to determine that before 11 Ma the Nubia-Somalia relative motion was faster than today and contained a significant strike-slip component.

Atlantic Ocean

The Atlantic Ocean is the second largest of the world's oceans, with an area of about 106,460,000 square kilometers (41,100,000 square miles). 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".

The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and the Americas to the west. As one component of the interconnected global ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica). The Equatorial Counter Current subdivides it into the North Atlantic Ocean and the South Atlantic Ocean at about 8°N.Scientific explorations of the Atlantic include the Challenger expedition, the German Meteor expedition, Columbia University's Lamont-Doherty Earth Observatory and the United States Navy Hydrographic Office.

Azores

The Azores ( ə-ZORZ or AY-zorz; Portuguese: Açores, [ɐˈsoɾɨʃ]), officially the Autonomous Region of the Azores (Região Autónoma dos Açores), is one of the two autonomous regions of Portugal (along with Madeira (Região Autónoma da Madeira)). It is an archipelago composed of nine volcanic islands in the North Atlantic Ocean about 1,360 km (850 mi) west of continental Portugal, about 1,643 km (1,021 mi) west of Lisbon, in continental Portugal, about 1,507 km (936 mi) northwest of Morocco, and about 1,925 km (1,196 mi) southeast of Newfoundland, Canada.

Its main industries are agriculture, dairy farming, livestock, fishing, and tourism, which is becoming the major service activity in the region. In addition, the government of the Azores employs a large percentage of the population directly or indirectly in the service and tertiary sectors. The main capital of the Azores is Ponta Delgada.

There are nine major Azorean islands and an islet cluster, in three main groups. These are Flores and Corvo, to the west; Graciosa, Terceira, São Jorge, Pico, and Faial in the centre; and São Miguel, Santa Maria, and the Formigas Reef to the east. They extend for more than 600 km (370 mi) and lie in a northwest-southeast direction.

All the islands have volcanic origins, although some, such as Santa Maria, have had no recorded activity since the islands were settled. Mount Pico, on the island of Pico, is the highest point in Portugal, at 2,351 m (7,713 ft). If measured from their base at the bottom of the ocean to their peaks, which thrust high above the surface of the Atlantic, the Azores are actually some of the tallest mountains on the planet.

The climate of the Azores is very mild for such a northerly location, being influenced by its distance from the continents and by the passing Gulf Stream. Due to the marine influence, temperatures remain mild year-round. Daytime temperatures normally fluctuate between 16 °C (61 °F) and 25 °C (77 °F) depending on season. Temperatures above 30 °C (86 °F) or below 3 °C (37 °F) are unknown in the major population centres. It is also generally wet and cloudy.

The culture, dialect, cuisine, and traditions of the Azorean islands vary considerably, because these once-uninhabited and remote islands were settled sporadically over a span of two centuries.

Azores Plateau

The Azores Plateau or Azores Platform is an oceanic plateau encompassing the Azores archipelago and the Azores Triple Junction in the North Atlantic Ocean. It was formed by the Azores hotspot 20 million years ago and is still associated with active volcanism.The plateau consists of a roughly triangular-shaped large igneous province that lies less than 2,000 m (6,600 ft) below sea level.

Azores–Gibraltar Transform Fault

The Azores–Gibraltar Transform Fault (AGFZ), also called a fault zone and a fracture zone, is a major seismic fault in the Central Atlantic Ocean west of the Strait of Gibraltar. It is the product of the complex interaction between the African, Eurasian, and Iberian plates.

The AGFZ produced the large-magnitude 1755 Lisbon and 1969 Horseshoe earthquakes and, consequently, a number of large tsunamis.

Charlie-Gibbs Fracture Zone

Charlie-Gibbs Fracture Zone is a system of two parallel fracture zones. It is the most prominent interruption of the Mid-Atlantic Ridge between the Azores and Iceland. It can be traced over more than 2000 kilometers, all the way from north-east of Newfoundland to south-west of Ireland. It took 90 million years for the fault to grow to this length.

List of Cumacea literature

Extensive literature list on Cumaceans.

Luckia

Luckia is a genus of amphipod crustaceans in the family Pontogeneiidae, with the sole species Luckia striki. It is found in hydrothermal vents in the Atlantic Ocean.

Oceanic plateau

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 184 oceanic plateaus covering an area of 18,486,600 km2 (7,137,700 sq mi), or about 5.11% of the oceans. 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 Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges.

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.

Outline of plate tectonics

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

Rainbow Vent Field

The Rainbow hydrothermal vent field is a system of ultramafic-hosted hydrothermal vents located at 36°14'N on the Mid-Atlantic Ridge (MAR). It was discovered in 1994 from temperature readings of ten high-temperature black smokers at a depth of approximately 2.3 kilometres (1.4 mi), where fluids can exceed 365 °C (689 °F). The site is shallower and larger in area than many other vent fields along the Azores section of the MAR with an area of 1.5 square kilometres (370 acres). Located 370 km (229.91 mi) southeast of Faial Island, it is a popular geochemical sampling and modeling site due to close proximity to the Azores and definitive representation of serpentinization from hydrothermal circulation and synthesis.Vent geology, biology, and fluid content make Rainbow comparable to other hot hydrothermal vents of the Azores such as Lucky Strike and Menez Gwen. However; chlorinity, metal concentration, and pH distinguish it from neighboring vent fields. As a hot, ultramafic-hosted vent field, pH levels of fluids are extremely low with lots of H2 and CH4 generated from water interactions with mafic igneous rocks.

Though not actively considered for development, Rainbow lies within the MoMAR (Monitoring of the Mid Atlantic Ridge) survey area for a marine observatory.

Terceira Rift

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.

Triple junction

A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of 3 types - a ridge (R), trench (T) or transform fault (F) - and triple junctions can be described according to the types of plate margin that meet at them (e.g. Transform-Transform-Trench, Ridge-Ridge-Ridge, or abbreviated F-F-T, R-R-R). Of the many possible types of triple junction only a few are stable through time ('stable' in this context means that the geometrical configuration of the triple junction will not change through geologic time). The meeting of 4 or more plates is also theoretically possible but junctions will only exist instantaneously.

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