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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. It crosses Terceira Island as a prominent ESE–WNW fissure zone.Volcanism Report on Terceira (Portugal) – February 2000 Smithsonian Institution Global Volcanism Program. Geological information The Terceira Rift is 550 km long, and represents the world's slowest spreading center, with plate divergence of 2–4 mm/year.Vogt, P. R., & Jung, W. Y. (2004). ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terceira From Space 2020
Terceira () is a volcanic island in the Azores archipelago, about a third of the way across the North Atlantic Ocean at a similar latitude to Portugal's capital Lisbon, with the island group forming an insular part of Portugal. It is one of the larger islands of the archipelago, with a population of 53,311 inhabitants in an area of approximately . Terceira is the location of the Azores' oldest city, Angra do Heroísmo, the historical capital of the archipelago and UNESCO World Heritage Site; the seat of the judicial system (Supreme Court); and the main insular Portuguese Air Force base, Lajes Field, Base Aérea nº 4 at Lajes, with a United States Air Force detachment. Terceira island has two main sea ports, one at Angra do Heroísmo and the other at Praia da Vitória, and a commercial airport integrated with the flight operations at Lajes Field, Base Aérea nº 4. The Portuguese bullfight is popular on the island, coming in two variations: the traditional equestrian bullfight ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spreading Center
Seafloor spreading, or seafloor spread, is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. History of study Earlier theories by Alfred Wegener and Alexander du Toit of continental drift postulated that continents in motion "plowed" through the fixed and immovable seafloor. The idea that the seafloor itself moves and also carries the continents with it as it spreads from a central rift axis was proposed by Harold Hammond Hess from Princeton University and Robert Dietz of the U.S. Naval Electronics Laboratory in San Diego in the 1960s. The phenomenon is known today as plate tectonics. In locations where two plates move apart, at mid-ocean ridges, new seafloor is continually formed during seafloor spreading. Significance Seafloor spreading helps explain continental drift in the theory of plate tectonics. When oceanic plates diverge, tensional stress causes fractures to occur in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 three 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. fault–fault–trench, ridge–ridge–ridge, or abbreviated F-F-T, R-R-R). Of the ten possible types of triple junctions 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 four or more plates is also theoretically possible, but junctions will only exist instantaneously. History The first scientific paper detailing the triple-junction concept was published in 1969 by Dan McKenzie and W. Jason Morgan. The term had traditionally been used for the intersection of three divergent boundaries or spreading ridges. These three divergent bounda ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 below sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical .... A lack of age progression amongst the younger submarine and subaerial volcanism combined with excess melting as evident from the shallow water depth and the presence of islands in the Azores suggest it may fit the waning mantle plume. References Plateaus of the Atlantic Ocean Mid-Atlantic Ridge Hotspot volcanism Large igneous provinces {{ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Plume
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. Concepts Mantle plumes were first proposed by J. Tuzo Wilson in 1963 and further developed by W. Jason Morgan in 1971 and 1972. A mantle plume is posited to exist where super-heated material forms ( nucleates) at the core-mantle boundary and rises through the Earth's mantle. Rather than a continuous stream, plumes should be viewed as a series of hot bubbles of material. Reaching the brittle upper Earth's crust they form diapirs. These diapirs are "hotspots" in the crust. In particular, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountain range in the world. In the North Atlantic, the ridge separates the North American plate, North American from the Eurasian plate and the African plate, north and south of the Azores triple junction. In the South Atlantic, it separates the African plate, African and South American plate, South American plates. The ridge extends from a junction with the Gakkel Ridge (Mid-Arctic Ridge) northeast of Greenland southward to the Bouvet triple junction in the South Atlantic. Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level, for example in Iceland. The ridge has an average spreading rate of about per year. Discovery A ridge under the northern Atlantic Ocean was first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southwest Indian Ridge
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 () in the Indian Ocean and Bouvet () in the Atlantic Ocean. Geological setting Spreading rates The spreading rate along the SWIR varies: the transition between slow (30 mm/yr) and ultra-slow (15 mm/yr) spreading occur at magnetic anomaly C6C (ca. 24 Ma). This occurs between 54°–67°E, the deepest, and perhaps coldest and most melt-poor, part of Earth's mid-ocean ridge system. Crustal thickness decreases quickly as spreading rates drop below c. 20 mm/yr and in the SWIR there is an absence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gakkel Ridge
The Gakkel Ridge (formerly known as the Nansen Cordillera and Arctic Mid-Ocean Ridge) is a mid-oceanic ridge, a divergent tectonic plate boundary between the North American Plate and the Eurasian Plate. It is located in the Eurasian Basin of the Arctic Ocean, between Greenland and Siberia. Geologically, it connects the northern end of the Mid-Atlantic Ridge with the Laptev Sea Rift. History The existence and approximate location of the Gakkel Ridge were predicted by Soviet polar explorer Yakov Yakovlevich Gakkel and confirmed on Soviet expeditions in the Arctic around 1950. The Ridge is named after him, and the name was recognized in April 1987 by SCUFN (under that body's old name, the Sub-Committee on Geographical Names and Nomenclature of Ocean Bottom Features). Until 1999, it was believed to be non-volcanic; that year, scientists operating from a nuclear submarine discovered active volcanoes along it. The largest, the Gakkel Ridge Caldera, is a supervolcano that erupte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transform Fault
A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduction, subduction zone. A transform fault is a special case of a ''strike-slip fault'' that also forms a plate boundary. Most such faults are found in oceanic crust, where they accommodate the lateral offset between segments of Divergent boundary, divergent boundaries, forming a zigzag pattern. This results from oblique seafloor spreading where the direction of motion is not perpendicular to the trend of the overall divergent boundary. A smaller number of such faults are found on land, although these are generally better-known, such as the San Andreas Fault and North Anatolian Fault. Nomenclature Transform boundaries are also known as conservative plate boundaries because they involve no addit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rift
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terceira Island
Terceira () is a volcanic island in the Azores archipelago, about a third of the way across the North Atlantic Ocean at a similar latitude to Portugal's capital Lisbon, with the island group forming an insular part of Portugal. It is one of the larger islands of the archipelago, with a population of 53,311 inhabitants in an area of approximately . Terceira is the location of the Azores' oldest city, Angra do Heroísmo, the historical capital of the archipelago and UNESCO World Heritage Site; the seat of the judicial system (Supreme Court); and the main insular Portuguese Air Force base, Lajes Field, Base Aérea nº 4 at Lajes, with a United States Air Force detachment. Terceira island has two main sea ports, one at Angra do Heroísmo and the other at Praia da Vitória, and a commercial airport integrated with the flight operations at Lajes Field, Base Aérea nº 4. The Portuguese bullfight is popular on the island, coming in two variations: the traditional equestrian bullfight ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
