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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.
The Mid-Atlantic Ridge is a mid-ocean ridge located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the 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 and South American plates. The ridge extends from a junction with the Gakkel 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 2.5 centimetres (1 in) per year.
An aulacogen is a failed arm of a triple junction. Aulacogens are a part of plate tectonics where oceanic and continental crust is continuously being created, destroyed, and rearranged on the Earth’s surface. Specifically, aulacogens are a rift zone, where new crust is formed, that is no longer active.
A rift valley is a linear shaped lowland between several highlands or mountain ranges produced by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear depression may subsequently be further deepened by the forces of erosion. More generally the valley is likely to be filled with sedimentary deposits derived from the rift flanks and the surrounding areas. In many cases rift lakes are formed. One of the best known examples of this process is the East African Rift. On Earth, rifts can occur at all elevations, from the sea floor to plateaus and mountain ranges in continental crust or in oceanic crust. They are often associated with a number of adjoining subsidiary or co-extensive valleys, which are typically considered part of the principal rift valley geologically.
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.
Arctica or Arctida was an ancient continent which formed approximately 2.565 billion years ago in the Neoarchean era. It was made of Archaean cratons, including the Siberian Craton, with its Anabar/Aldan shields in Siberia, and the Slave, Wyoming, Superior, and North Atlantic cratons in North America. Arctica was named by Rogers 1996 because the Arctic Ocean formed by the separation of the North American and Siberian cratons. Russian geologists writing in English call the continent "Arctida" since it was given that name in 1987, alternatively the Hyperborean craton, in reference to the hyperboreans in Greek mythology.
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. Of the ten possible types of triple junctions only a few are stable through time. The meeting of four or more plates is also theoretically possible but junctions will only exist instantaneously.
Lancaster Sound is a body of water in the Qikiqtaaluk Region, Nunavut, Canada. It is located between Devon Island and Baffin Island, forming the eastern entrance to the Parry Channel and the Northwest Passage. East of the sound lies Baffin Bay; to the west lies Viscount Melville Sound. Further west a traveller would enter the M'Clure Strait before heading into the Arctic Ocean.
Prince Regent Inlet is a body of water in Nunavut, Canada between the west end of Baffin Island and Somerset Island on the west. It opens north into Lancaster Sound and to the south merges into the Gulf of Boothia. The Arctic inlet's northern portion is approximately 40 mi (64 km) wide; the southern portion is approximately 65 mi (105 km) wide. It is deep throughout and there are no islands within the inlet.
The Sverdrup Basin Magmatic Province is a large igneous province located on Axel Heiberg Island and Ellesmere Island, Nunavut, Canada near the rifted margin of the Arctic Ocean at the end of Alpha Ridge.
This is a list of articles related to plate tectonics and tectonic plates.
The Poseidon Ocean was an ocean that existed during the Mesoproterozoic period of the geologic timescale. It began to form when a hotspot collided with lithosphere that was already in an extensional regime that allowed rifting to occur at the onset of hotspot volcanism that created the Mackenzie Large Igneous Province. This hotspot, known as the carlisle united, produced passive rifting to form a triple junction. As two of the rift arms continued to grow, they created the Poseidon Ocean basin. The third rift arm failed to open fully, creating an aulacogen.
The Nipigon Embayment is an inactive continental rift zone in Northwestern Ontario, Canada, centered on Lake Nipigon. It represents an aulacogen of the much larger Midcontinent Rift System, which formed some 1,100 million years ago when the North American craton began to split apart during the Proterozoic eon.
Tectonic subsidence is the sinking of the Earth's crust on a large scale, relative to crustal-scale features or the geoid. The movement of crustal plates and accommodation spaces produced by faulting brought about subsidence on a large scale in a variety of environments, including passive margins, aulacogens, fore-arc basins, foreland basins, intercontinental basins and pull-apart basins. Three mechanisms are common in the tectonic environments in which subsidence occurs: extension, cooling and loading.
The Chukchi Plateau or Chukchi Cap is a large subsea formation extending north from the Alaskan margin into the Arctic Ocean. The ridge is normally covered by ice year-round, and reaches an approximate bathymetric prominence of 3,400 m with its highest point at 246 m below sea level. As a subsea ridge extending from the continental shelf of the United States north of Alaska, the Chukchi Plateau is an important feature in maritime law of the Arctic Ocean and has been the subject of significant geographic research. The ridge has been extensively mapped by the USCGC Healy, and by the Canadian icebreaker CCGS Louis S. St-Laurent in 2011 and RV Marcus Langseth, a National Science Foundation vessel operated by the Lamont–Doherty Earth Observatory of Columbia University.
The Southern Oklahoma Aulacogen(ah-lah-coh-jin) (help·info) is a failed rift, or failed rift arm (aulacogen), of the triple junction that became the Iapetus Ocean spreading ridges. It is a significant geological feature in the Western and Southern United States. It formed sometime in the early to mid Cambrian Period and spans the Wichita Mountains, Taovayan Valley, Anadarko Basin, and Hardeman Basin in Southwestern Oklahoma. The Southern Oklahoma Aulacogen is primarily composed of basaltic dikes, gabbros, and units of granitic rock.
The Canadian Arctic Rift System is a major North American geological structure extending from the Labrador Sea in the southeast through Davis Strait, Baffin Bay and the Arctic Archipelago in the northwest. It consists of a series of interconnected rifts that formed during the Paleozoic, Mesozoic and Cenozoic eras. Extensional stresses along the entire length of the rift system have resulted in a variety of tectonic features, including grabens, half-grabens, basins and faults.
The Eurekan orogeny was a Phanerozoic mountain building event that affected the eastern portion of the Arctic Archipelago and, to a lesser extent, northern Greenland. Deformation initiated in the Late Cretaceous, during which time the Sverdrup Basin began to fragment and fold in response to the counterclockwise rotation of Greenland, caused by seafloor spreading in the Canadian Arctic Rift System. Isostatic uplift was most pronounced in the Grantland Mountains and Victoria and Albert Mountains on Ellesmere Island and in the Princess Margaret Range on Axel Heiberg Island, as evidenced by the current physiography. Compression in a broad zone on Ellesmere Island resulted in the formation of the Eurekan Fold Belt.
The New Mexico Aulacogen(ah-lah-coh-jin) (help·info) is a failed rift, or failed rift arm (aulacogen), that may have formed during the Cambrian and Ordovician Periods in the area from central Colorado through southern New Mexico. Its presence is inferred from pervasive alkaline and carbonatite intrusions of this age in this area. These include the Iron Hill carbonatite complex of central Colorado. A smaller alkali-carbonatite complex at Lobo Hill returns an Ar-Ar age of 518 ± 5.7 million years. The Florida Mountains uplift took place at about this same time and may be associated with this aulacogen.
References
- ↑ Kerr, J. Wm. (1979). "Structural Framework of Lancaster Aulacogen, Arctic Canada". Open File 619. Geological Survey of Canada: 31.
- ↑ E. M. Nairn, Alan; Churkin, Jr., Michael; G. Stehli, Francis (1981). The Ocean Basins and Margins: The Arctic Ocean. Vol. 5. Springer Science+Business Media. p. 166. ISBN 978-1-4757-1250-6.
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