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34-614: The Caledonian Wilson cycle commenced with the continental break-up of Rodinia and the opening of the Iapetus ocean about 616–583 Ma ( mega-annum ) ago. The Iapetus was at its widest in the Late Cambrian – Early Ordovician before it began to close by subduction of Iapetus crust along the Gondawanan and Laurentian margins starting between 500 and 488 Ma ago. Subduction of Iapteus crust continued until about 430 Ma ago until

68-582: A colleague and friend of Wilson. The Wilson cycle theory is based upon the idea of an ongoing cycle of ocean closure, continental collision , and a formation of new ocean on the former suture zone. The Wilson Cycle can be described in six phases of tectonic plate motion: the separation of a continent (continental rift ), formation of a young ocean at the seafloor, formation of ocean basins during continental drift , initiation of subduction , closure of ocean basins due to oceanic lithospheric subduction, and finally, collision of two continents and closure of

102-469: A global ocean model. These trajectories are of particles that move only on the surface of the ocean. The model outcome gives the probability of a particle at a certain grid point to end up somewhere else on the ocean's surface. With the model outcome a matrix can be created from which the Eigenvectors and Eigenvalues are taken. These Eigenvectors show regions of attraction, aka regions where things on

136-504: A particle on the ocean surface in a certain region is more likely to stay in the same region than to pass over to a different one. Depending on the chemical composition and the physical state, the Earth can be divided into three major components:  the mantle , the core , and the crust . The crust is referred to as the outside layer of the Earth. It is made of solid rock, mostly basalt and granite . The crust that lies below sea level

170-555: Is affected not only by the volume of the ocean basin, but also by the volume of water in them. Factors that influence the volume of the ocean basins are: The Atlantic Ocean and the Arctic Ocean are good examples of active, growing oceanic basins, whereas the Mediterranean Sea is shrinking. The Pacific Ocean is also an active, shrinking oceanic basin, even though it has both spreading ridge and oceanic trenches. Perhaps

204-532: Is known as the oceanic crust , while on land it is known as the continental crust . The former is thinner and is composed of relatively dense basalt, while the latter is less dense and mainly composed of granite. The lithosphere is composed of the crust (oceanic and continental) and the uppermost part of the mantle. The lithosphere is broken into sections called plates . Tectonic plates move very slowly (5 to 10 cm (2 to 4 inches) per year) relative to each other and interact along their boundaries. This movement

238-737: Is only a tiny "mountain root" beneath the southern Scandinavian Mountains and no "root" at all in the north. Further, the Caledonian Mountains in Scandinavia are known to have undergone orogenic collapse for a long period starting in the Devonian . Another problem with this model is that it does not explain why other former mountains dating back to the Caledonian orogeny are eroded and buried in sediments and not uplifted by their "roots". Others claim that molten magma exists below

272-604: Is responsible for most of the Earth's seismic and volcanic activity. Depending on how the plates interact with each other, there are three types of boundaries. The Earth's deepest trench is the Mariana Trench which extends for about 2500 km (1600 miles) across the seabed. It is near the Mariana Islands , a volcanic archipelago in the West Pacific. Its deepest point is 10994 m (nearly 7 miles) below

306-497: Is set at the equator . The Antarctic or Southern Ocean, which reaches from 60° south to Antarctica had been omitted until 2000, but is now also recognized by the International Hydrographic Office. Nevertheless, and since ocean basins are interconnected, many oceanographers prefer to refer to one single ocean basin instead of multiple ones.   Older references (e.g., Littlehales 1930) consider

340-609: Is termed the Wilson Cycle, or the more encompassing Supercontinent Cycle, the tectonic episodicity identified by Tuzo Wilson in his 1966 paper defines a fundamental aspect of Earth's tectonic, climatic and biogeochemical evolution over much of its history." Oceanic basin In  hydrology , an  oceanic basin  (or ocean basin ) is anywhere on Earth that is covered by  seawater . Geologically , most of the ocean basins are large  geologic basins  that are below sea level . Most commonly

374-559: The Archean Eon . The Wilson Cycle model was a key development in the theory of plate tectonics during the Plate Tectonics Revolution . The model is named after John Tuzo Wilson in recognition of his iconic observation that the present-day Atlantic Ocean appears along a former suture zone and his development in a classic 1968 paper of what was later named the "Wilson cycle" in 1975 by Kevin C. A. Burke ,

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408-866: The Baltic Sea (with three subdivisions), the North Sea , the Greenland Sea , the Norwegian Sea , the Laptev Sea , the Gulf of Mexico , the South China Sea , and many more. The limits were set for convenience of compiling sailing directions but had no geographical or physical ground and to this day have no political significance. For instance, the line between the North and South Atlantic

442-658: The Congo-Sao Francisco Craton around 112 Ma. Following the North Atlantic Igneous Province eruptions around 55 Ma, the northern Atlantic passive margins rifted to their present state. From the case of the Atlantic Ocean, Wilson Cycle plate margins can broadly be described as having the following attributes: A Wilson cycle is distinct from the supercontinent cycle , which is the break-up of one supercontinent and

476-804: The Atlantic and Arctic basins. The Atlantic Basin began to form around 180 million years ago, when the continent Laurasia (North America and Eurasia ) started to drift away from Africa and South America. The Pacific plate grew, and subduction led to a shrinking of its bordering plates. The Pacific plate continues to move northward. Around 130 million years ago the South Atlantic started to form, as South America and Africa started to separate. At around this time India and Madagascar rifted northwards, away from Australia and Antarctica, creating seafloor around Western Australia and East Antarctica. When Madagascar and India separated between 90 and 80 million years ago,

510-560: The Caledonides of Norway, causing the uplift. Wilson cycle The Wilson Cycle is a model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents . A classic example of the Wilson Cycle is the opening and closing of the Atlantic Ocean . It has been suggested that Wilson cycles on Earth started about 3 Ga in

544-460: The Earth's surface, and together they contain almost 97% of all water on the planet. They have an average depth of almost 4 km (about 2.5 miles). "Limits of Oceans and Seas" , published by the International Hydrographic Office in 1953, is a document that defined the ocean's basins as they are largely known today. The main ocean basins are the ones named in the previous section. These main basins are divided into smaller parts. Some examples are:

578-617: The Mariana Islands. It is located far away from oceanic spreading centers, where oceanic crust is constantly created or destroyed. The oldest crust is estimated to be only around 200 million years old, compared to the age of Earth which is 4.6 billion years. 200 million years ago nearly all land mass was one large continent called Pangea , which started to split up. During the splitting process of Pangea, some ocean basins shrunk, such as the Pacific, while others were created, such as

612-616: The Scandinavian Caledonides and the Scandinavian Mountains has led to various suggestions that the modern Scandinavian Mountains are a remnant of the Caledonide mountains. A version of this argument was put forward in 2009 with the claim that the uplift of the mountains was attained by buoyancy of the surviving "mountain roots" of the Caledonian orogen. This concept has been criticized because there

646-510: The development of another and takes place on a global scale. The Wilson cycle rarely synchronizes with the timing of a supercontinent cycle. However, both supercontinent cycles and Wilson cycles were involved in the formation of Pangaea and of Rodinia . The 50-year retrospective in the Geological Society of London Special Paper 470 provides an excellent nuanced view of how these concepts fit together. They conclude, "Whether it

680-527: The final continental collision of Laurentia with Baltica, i.e. the Scandian phase of the Caledonian orogeny. The time of the continental collision is estimated by the cessation of subduction-related magmatism and a common apparent polar wander path ( APWP ) for Laurentia and Baltica. During the collision, the Baltican continental margin was deeply subducted beneath Laurentia and eclogitized . The time of

714-570: The high correlation of ages of large igneous provinces and the break-up age for these margins. A case study of the Wilson Cycle can be seen with the development of the Atlantic Ocean. Various parts of the modern day Atlantic Ocean opened at different times over the Mesozoic to Cenozoic periods following the Wilson Cycle. Seafloor spreading in the central Atlantic Ocean likely occurred around 134-126 Ma on Pan-African Orogenic and Rheic sutures. South Atlantic Ocean seafloor spreading began along

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748-572: The individual ocean basins has fluctuated in the past due to, amongst other, tectonic plate movements. Therefore, an oceanic basin can be actively changing size and/or depth or can be relatively inactive. The elements of an active and growing oceanic basin include an elevated mid-ocean ridge , flanking abyssal hills leading down to abyssal plains and an oceanic trench . Changes in biodiversity, floodings and other climate variations are linked to sea-level, and are reconstructed with different models and observations (e.g., age of oceanic crust). Sea level

782-492: The maximal burial of the Baltican margin is estimated at 410 Ma ago by radiometric age dating of the ultra-high pressure (UHP) metamorphism in the Western Gneiss Region (WGR). Also during the collision, the Caledonian allochthons were thrust over the Baltican margin. Peak metamorphism in the allochthons is estimated to have occurred somewhat earlier than in the autochthon at about 420 Ma ago. Following

816-618: The much older Svecokarelian and Sveconorwegian provinces . The Caledonian rocks form large nappes ( Swedish : skollor ) that have been thrust over the older rocks. Much of the Caledonian rocks have been eroded since they were put in place meaning that they were once thicker and more contiguous. It is also implied from the erosion that the nappes of Caledonian rock originally reached further east than they do today. The erosion has left remaining massifs of Caledonian rocks and windows of Precambrian -aged rock. While there are some disagreements, geologists generally recognize four units among

850-495: The nappes: an Uppermost, an Upper, a Middle and a Lower one. The last one is made up Ediacaran ( Vendian ), Cambrian , Ordovician and Silurian -aged sedimentary rocks . Pieces of Precambrian shield rocks are in some places also incorporated into the Lower nappes. Despite occurring in roughly the same area, the ancient Scandinavian Caledonian Mountains and the modern Scandinavian Mountains are not synonymous. The overlap between

884-586: The ocean basins. The first three stages (Embryonic, Young, Mature) describe the widening of the ocean and the last three stages (Declining, Terminal, and Relic Scar/Geosuture) describe the closing of the ocean and creation of mountain ranges like the Himalayas . In the 21st century, insights from seismic imaging and other techniques have led to updates to the Wilson Cycle to include relationships between activation of rifting and mantle plumes . Plume-induced rifting and rifting-induced mantle upwelling can explain

918-576: The ocean is divided into basins following the continents distribution : the North and South Atlantic (together approximately 75 million km / 29 million mi ), North and South Pacific (together approximately 155 million km / 59 million mi ), Indian Ocean (68 million km / 26 million mi ) and Arctic Ocean (14 million km / 5.4 million mi ). Also recognized is the Southern Ocean (20 million km / 7 million mi ). All ocean basins collectively cover 71% of

952-406: The ocean is very slow compared to horizonal flow and observing the deep ocean is difficult. Defining the ocean basins based on connectivity of the entire ocean (depth and width) is therefore not possible. Froyland et al. (2014) defined ocean basins based on surface connectivity. This is achieved by creating a Markov Chain model of the surface ocean dynamics using short term time trajectory data from

986-440: The oceanic basins to be the complement to the continents , with erosion dominating the latter, and the sediments so derived ending up in the ocean basins. This vision is supported by the fact that oceans lie lower than continents, so the former serve as sedimentary basins that collect sediment eroded from the continents, known as clastic sediments, as well as precipitation sediments. Ocean basins also serve as repositories for

1020-455: The skeletons of carbonate - and silica -secreting organisms such as coral reefs , diatoms , radiolarians , and foraminifera . More modern sources (e.g., Floyd 1991) regard the ocean basins more as basaltic plains, than as sedimentary depositories, since most sedimentation occurs on the continental shelves and not in the geologically defined ocean basins. The flow in the ocean is not uniform but varies with depth. Vertical circulation in

1054-609: The spreading ridges in the Indian Ocean were reorganized. The northernmost part of the Atlantic Ocean was also formed at this time when Europe and Greenland separated. About 60 million years ago a new rift and oceanic ridge formed between Greenland and Europe, separating them and initiating the formation of oceanic crust in the Norwegian Sea and the Eurasian Basin in the eastern Arctic Ocean. The area occupied by

Scandinavian Caledonides - Misplaced Pages Continue

1088-617: The subduction of the Baltican continental margin and thrusting of the nappes over the Baltican basement, the orogen began to collapse in the Early Devonian , which was associated with extensional tectonics and sinistral motion between the Laurentian and Baltican tectonic plates. The Caledonian orogeny put in place most of the bedrock now seen in the Scandinavian Mountains . Caledonian rocks overlie rocks of

1122-489: The surface of the ocean (plastic, biomass, water etc.) become trapped. One of these regions is for example the Atlantic garbage patch . With this approach the five main ocean basins are still the North and South Atlantic, North and South Pacific and the Arctic Ocean, but with different boundaries between the basins. These boundaries show the lines of very little surface connectivity between the different regions which means that

1156-492: The surface of the sea. The Earth's longest trench runs alongside the coast of Peru and Chile, reaching a depth of 8065 m (26460 feet) and extending for approximately 5900 km (3700 miles). It occurs where the oceanic Nazca plate slides under the continental South American plate and is associated with the upthrust and volcanic activity of the Andes. The oldest oceanic crust is in the far western equatorial Pacific, east of

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