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Cratonization
A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates; the exceptions occur where geologically recent rifting events have separated cratons and created passive margins along their edges. Cratons are characteristically composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep lithospheric roots that extend as much as several hundred kilometres into Earth's mantle. Terminology The term ''craton'' is used to distinguish the stable portion of the continental crust from regions that are more geologically active and unstable. Cratons are composed of two layers: A continental '' shield'', in which the basement rock crops out at the surfa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dharwar Craton
The Dharwar Craton is an Archean continental crust craton formed between 3.6-2.5 billion years ago ( Ga), which is located in southern India and considered as the oldest part of the Indian peninsula. Studies in the 2010s suggest that the craton can be separated into three crustal blocks since they show different accretionary history (i.e., the history of block collisions). The craton includes the western, central and eastern blocks and the three blocks are divided by several shear zones. The lithologies of the Dharwar Craton are mainly TTG (Tonalite-trondhjemite-granodiorite) gneisses, volcanic-sedimentary greenstone sequences and calc-alkaline granitoids. The western Dharwar Craton contains the oldest basement rocks, with greenstone sequences between 3.0-3.4 Ga, whereas the central block of the craton mainly contains migmatitic TTG gneisses, and the eastern block contains 2.7 Ga greenstone belts and calc-alkaline plutons. The formation of the basement rock of the Dharwar C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle (Earth), upper mantle are distinguished on the basis of chemistry and mineralogy. Earth's lithosphere Earth's lithosphere, which constitutes the hard and rigid outer vertical layer of the Earth, includes the crust and the uppermost mantle. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle. The lithosphere–asthenosphere boundary is defined by a difference in response to stress. The lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plasticity (physics), pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hans Stille
Hans Wilhelm Stille (8 October 1876 – 26 December 1966) was an influential German geologist working primarily on tectonics and the collation of tectonic events during the Phanerozoic. Stille adhered to the contracting Earth hypothesis and together with Leopold Kober he worked on the geosyncline theory to explain orogeny. Şengör (1982), p. 23 Stille's ideas emerged in the aftermath of Eduard Suess' book ''Das Antlitz der Erde'' (1883–1909). Stille's and Kober's school of thought was one of two that emerged in the post-Suess era the other being headed by Alfred Wegener and Émile Argand. This competing view rejected Earth contraction and argued for continental drift. Şengör (1982), p. 24 As Stille opposed continental drift he came to be labelled a "fixist". Şengör (1982), p. 30 Part of Stille's work dealt with massifs and sedimentary basins in Central Europe; differing from Suess' interpretations for the same area showing that between the Bohemian and Rhine massifs Mesoz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy. Earth's lithosphere Earth's lithosphere, which constitutes the hard and rigid outer vertical layer of the Earth, includes the crust and the uppermost mantle. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle. The lithosphere–asthenosphere boundary is defined by a difference in response to stress. The lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation. The thickness of the lithosphere is thus considered to b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismic Tomography
Seismic tomography or seismotomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. The data received at seismometers are used to solve an inverse problem, wherein the locations of reflection and refraction of the wave paths are determined. This solution can be used to create 3D images of velocity anomalies which may be interpreted as structural, thermal, or compositional variations. Geoscientists use these images to better understand core, mantle, and plate tectonic processes. Theory Tomography is solved as an inverse problem. Seismic travel time data are compared to an initial Earth model and the model is modified until the best possible fit between the model predictions and observed data is found. Seismic waves would travel in straight lines ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Australia
South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories by area, and second smallest state by population. It has a total of 1.8 million people. Its population is the second most highly centralised in Australia, after Western Australia, with more than 77 percent of South Australians living in the capital Adelaide, or its environs. Other population centres in the state are relatively small; Mount Gambier, the second-largest centre, has a population of 33,233. South Australia shares borders with all of the other mainland states, as well as the Northern Territory; it is bordered to the west by Western Australia, to the north by the Northern Territory, to the north-east by Queensland, to the east by New South Wales, to the south-east by Victoria, and to the south by the Great Australian Bight.M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gawler Craton
The Gawler Craton covers approximately 440,000 square kilometres of central South Australia. Its Precambrian crystalline basement (geology), basement Crust (geology), crustal block (geology), block was cratonised ca. 1550–1450 Ma. Prior to 1550 Ma the craton comprised a number of active Proterozoic orogenic belts extending back in time to at least 2450 Ma. The Craton can be subdivided into a number of tectonic subdomains on the basis of structure and tectonostratigraphy, stratigraphic history. The south-central Eyre Peninsula straddles the boundary between the Archean, Archaean to early Palaeoproterozoic Coulta Subdomain and the Cleve Subdomain, a Palaeoproterozoic orogenic belt ("mobile zone") probably representing a shelf or basinal depository for the Hutchison Group (ca. 1900–1845 Ma) prior to its deformation during the Kimban orogeny (ca. 1845–1710 Ma). On northeastern Eyre Peninsula, the Cleve Subdomain is bounded by the slightly younger Moonta Subdomain which is cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Craton
North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north'' is related to the Old High German ''nord'', both descending from the Proto-Indo-European unit *''ner-'', meaning "left; below" as north is to left when facing the rising sun. Similarly, the other cardinal directions are also related to the sun's position. The Latin word ''borealis'' comes from the Greek '' boreas'' "north wind, north", which, according to Ovid, was personified as the wind-god Boreas, the father of Calais and Zetes. ''Septentrionalis'' is from ''septentriones'', "the seven plow oxen", a name of ''Ursa Major''. The Greek ἀρκτικός (''arktikós'') is named for the same constellation, and is the source of the English word ''Arctic''. Other languages have other derivations. For example, in Lezgian, ''kefer'' can mean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countries of Namibia, Botswana, and Zimbabwe; and to the east and northeast by Mozambique and Eswatini. It also completely enclaves the country Lesotho. It is the southernmost country on the mainland of the Old World, and the second-most populous country located entirely south of the equator, after Tanzania. South Africa is a biodiversity hotspot, with unique biomes, plant and animal life. With over 60 million people, the country is the world's 24th-most populous nation and covers an area of . South Africa has three capital cities, with the executive, judicial and legislative branches of government based in Pretoria, Bloemfontein, and Cape Town respectively. The largest city is Johannesburg. About 80% of the population are Black South Afri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaapvaal Craton
The Kaapvaal Craton (centred on Limpopo Province in South Africa), along with the Pilbara Craton of Western Australia, are the only remaining areas of pristine 3.6–2.5 Ga (billion years ago) crust on Earth. Similarities of rock records from both these cratons, especially of the overlying late Archean sequences, suggest that they were once part of the Vaalbara supercontinent. Description The Kaapvaal Craton covers an area of approximately and is joined to the Zimbabwe Craton to the north by the Limpopo Belt. To the south and west, the Kaapvaal Craton is flanked by Proterozoic orogens, and to the east by the Lebombo monocline that contains Jurassic igneous rocks associated with the break-up of Gondwana. The Kaapvaal Craton formed and stabilised between 3.7 and 2.6 Ga by the emplacement of major granitoid batholiths that thickened and stabilised the continental crust during the early stages of an arc-related magmatism and sedimentation cycle. The craton is a mixture o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southern subregion of a single continent called America. South America is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean; North America and the Caribbean Sea lie to the northwest. The continent generally includes twelve sovereign states: Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Suriname, Uruguay, and Venezuela; two dependent territories: the Falkland Islands and South Georgia and the South Sandwich Islands; and one internal territory: French Guiana. In addition, the ABC islands of the Kingdom of the Netherlands, Ascension Island (dependency of Saint Helena, Ascension and Tristan da Cunha, a British Overseas Territory), Bouvet Island ( dependency of Norway), Pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amazonian Shield
The Amazonian Craton is a geologic province located in South America. It occupies a large portion of the central, north and eastern part of the continent and represents one of Earth's largest cratonic regions. The Guiana Shield and Central Brazil Shield (Guaporé Shield) constitute respectively the northern and southern exhumed parts of the craton. Between the two shields lies the Amazon Rift, a zone of weakness within the craton. Smaller cratons of Precambrian rocks south of the Amazonian Shield are the Río de la Plata Craton and the São Francisco Craton, which lies to the east. The Río Apa Craton at the Paraguay-Brazil border is considered be likely just the southern part of the Amazonian Craton. The rocks of Río Apa were deformed during the Sunsás orogeny. It has been suggested that the Late Mesoproterozoic– Early Neoproterozoic aged Sveconorwegian Orogen in Fennoscandia could have been caused by a continent–continent collision between the Amazonia and Balti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
