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An orogeny is an event that leads to both structural deformation and compositional differentiation of the Earth's lithosphere at convergent plate margins. An orogen or orogenic belt develops when a continental plate crumples and is uplifted to form one or more mountain ranges; this involves a series of geological processes collectively called orogenesis.
The Alps form part of a Cenozoic orogenic belt of mountain chains, called the Alpide belt, that stretches through southern Europe and Asia from the Atlantic all the way to the Himalayas. This belt of mountain chains was formed during the Alpine orogeny. A gap in these mountain chains in central Europe separates the Alps from the Carpathians to the east. Orogeny took place continuously and tectonic subsidence has produced the gaps in between.
In geomorphology and geology, a peneplain is a low-relief plain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage of peneplain is meant to imply the representation of a near-final stage of fluvial erosion during times of extended tectonic stability. Peneplains are sometimes associated with the cycle of erosion theory of William Morris Davis, but Davis and other workers have also used the term in a purely descriptive manner without any theory or particular genesis attached.
The Baltic Shield is a segment of the Earth's crust belonging to the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean and Proterozoic gneisses and greenstone which have undergone numerous deformations through tectonic activity. It contains the oldest rocks of the European continent with a thickness of 250-300 km.
A craton 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. They 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.
Mountain formation refers to the geological processes that underlie the formation of mountains. These processes are associated with large-scale movements of the Earth's crust. Folding, faulting, volcanic activity, igneous intrusion and metamorphism can all be parts of the orogenic process of mountain building. The formation of mountains is not necessarily related to the geological structures found on it.
Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thickening, changes in the density distribution of the crust and underlying mantle, and flexural support due to the bending of rigid lithosphere.
The interaction between erosion and tectonics has been a topic of debate since the early 1990s. While the tectonic effects on surface processes such as erosion have long been recognized, the opposite has only recently been addressed. The primary questions surrounding this topic are what types of interactions exist between erosion and tectonics and what are the implications of these interactions. While this is still a matter of debate, one thing is clear, the Earth's landscape is a product of two factors: tectonics, which can create topography and maintain relief through surface and rock uplift, and climate, which mediates the erosional processes that wear away upland areas over time. The interaction of these processes can form, modify, or destroy geomorphic features on the Earth's surface.
The Scandinavian Mountains or the Scandes is a mountain range that runs through the Scandinavian Peninsula. The Scandinavian Mountains are often erroneously thought to be equivalent to the Scandinavian Caledonides, an ancient mountain range and orogen covering roughly the same area. The western sides of the mountains drop precipitously into the North Sea and Norwegian Sea, forming the fjords of Norway, whereas to the northeast they gradually curve towards Finland. To the north they form the border between Norway and Sweden, reaching 2,000 metres (6,600 ft) high at the Arctic Circle. The mountain range just touches northwesternmost Finland but are scarcely more than hills at their northernmost extension at the North Cape (Nordkapp).
A river anticline is a geologic structure that is formed by the focused uplift of rock caused by high erosion rates from large rivers relative to the surrounding areas. An anticline is a fold that is concave down, whose limbs are dipping away from its axis, and whose oldest units are in the middle of the fold. These features form in a number of structural settings. In the case of river anticlines, they form due to high erosion rates, usually in orogenic settings. In a mountain building setting, like that of the Himalaya or the Andes, erosion rates are high and the river anticline's fold axis will trend parallel to a major river. When river anticlines form, they have a zone of uplift between 50-80 kilometers wide along the rivers that form them.
The main points that are discussed in the geology of Iran include the study of the geological and structural units or zones; stratigraphy; magmatism and igneous rocks; ophiolite series and ultramafic rocks; and orogenic events in Iran.
The geology of South Africa is highly varied including cratons, greenstone belts, large impact craters as well as orogenic belts. The geology of the country is the base for a large mining sector that extracts gold, diamonds, iron and coal from world-class deposits. The geomorphology of South Africa consists of a high plateau rimmed to west, south and southeast by the Great Escarpment and rugged mountains beyond this there is strip of narrow coastal plain.
The sub-Cambrian peneplain is an ancient, extremely flat, erosion surface (peneplain) that has been exhumed and exposed by erosion from under Cambrian strata over large swathes of Fennoscandia. Eastward, where this peneplain dips below Cambrian and other Lower Paleozoic cover rocks. The exposed parts of this peneplain are extraordinarily flat with relief of less than 20 m. The overlying cover rocks demonstrate that the peneplain was flooded by shallow seas during the Early Paleozoic. Being the oldest identifiable peneplain in its area the Sub-Cambrian peneplain qualifies as a primary peneplain.
The South Swedish highlands or South Swedish Uplands is a hilly area covering large parts of Götaland in southern Sweden. Except for a lack of deep valleys, the landscape is similar to the Norrland terrain found further north in Sweden. The central-eastern parts of the highlands contain about thirty narrow canyons locally known as skurus.
In geology, the term exhumation refers to the process by which a parcel of rock, approaches Earth's surface.
The South Småland peneplain is a large flattish erosion surface, a peneplain, formed during the Tertiary, covering large swathes of southern Småland and nearby areas in Southern Sweden. To the east the South Småland peneplain bounds with the Sub-Cambrian peneplain uphill across an escarpment. While is almost as flat as the Sub-Cambrian peneplain the South Småland peneplain differs in that it contain far more residual hills and that it has never been covered by sedimentary rocks. To the south and west the peneplain transitions into Mesozoic-aged hilly surfaces.
The paleic surface or palaeic surface is an erosion surface of gentle slopes that exist in South Norway. Parts of it are a continuation of the Sub-Cambrian peneplain and Muddus Plains found further east or equivalent to the strandflat coastal plains of Norway. Hardangervidda, a particularly flat and elevated part of the Paleic surface formed in the Miocene at sea level.
Huangling Complex represents a group of rock units appear in the middle of Yangtze Block in South China, distributed across Yixingshan, Zigui, Huangling and Yichang counties. The group of rock involves nonconformity that sedimentary rocks overlie the metamorphic basement. It is a 73-km long, asymmetrical dome-shaped anticline with axial plane orientating in north-south direction. It has a steeper west flank and a gentler east flank. Basically, there are three tectonic units from the anticline core to the rim, including Archean to Paleoproterozoic metamorphic basement, Neoproterozoic to Jurassic sedimentary rocks and Cretaceous fluvial deposit sedimentary cover. The northern part of the core is mainly tonalite-trondhjemite-gneiss (TTG) and Cretaceous sedimentary rock, it is called the Archean Kongling Complex. The middle of the core is mainly the Neoproterozoic granitoid. The southern part of the core is the Neoproterozoic potassium granite. Two basins are situated on the western and eastern flanks of the core respectively, including the Zigui basin and Dangyang basin. Both basins are synforms while Zigui basin has a larger extent of folding. Yuanan Graben and Jingmen Graben are found within Dangyang Basin area. Huangling Complex is an important area that helps unravel the tectonic history of South China Craton because it has well-exposed layers of rock units from Archean basement rock to Cretaceous sedimentary rock cover due to the erosion of the anticline.
A piedmonttreppen or piedmont benchland is a conceived landform consisting in a succession of benches at different heights and that forms in sequence during the uplift of a geological dome. The concept was first proposed in a posthumous publication by Walther Penck in 1924.
The South China Craton or South China Block is one of the Precambrian continental blocks in China. It is traditionally divided into the Yangtze Block in the NW and the Cathaysia Block in the SE. The Jiangshan–Shaoxing Fault represents the suture boundary between the two sub-blocks. Recent study suggests that the South China Block possibly has one more sub-block which is named the Tolo Terrane. The oldest rocks in the South China Block occur within the Kongling Complex, which yields zircon U–Pb ages of 3.3–2.9 Ga.
References
- ↑ Arthur Holmes; Doris L. Holmes (2004). Holmes principles of physical geology (4th ed.). Taylor & Francis. p. 92. ISBN 0-7487-4381-2.
- ↑ Richard J. Huggett (2003). Fundamentals of geomorphology. Routledge. p. 76. ISBN 0-415-24146-4.
- ↑ Şengör, A.M.C. (2001). "Elevation as an indicator of mantle-plume activity". In Richard E. Ernst, Kenneth L. Buchan (ed.). Mantle plumes: their identification through time. Geological Society of America. p. 215. ISBN 0-8137-2352-3.
- ↑ Holford, S.P.; et al. (2008). "Neogene exhumation in the Irish Sea area". In Johnson, =Howard; et al. (eds.). The nature and origin of compression in passive margins. Geological Society. p. 112. ISBN 1-86239-261-7.
- ↑ Frank Northen Magill (1990). Magill's survey of science: Earth science series, Volume 5. Salem Press. p. 2498. ISBN 0-89356-611-X.
- ↑ Robert J. Twiss, Eldridge M. Moores (1992). Structural geology (2nd ed.). Macmillan. p. 217. ISBN 0-7167-2252-6.
Orogenic belts are all characterized by a number of fold systems.
- 1 2 3 4 Lidmar-Bergström, Karna; Olvmo, Mats; Bonow, Johan M. (2017). "The South Swedish Dome: a key structure for identification of peneplains and conclusions on Phanerozoic tectonics of an ancient shield". GFF .
- 1 2 Moore, A.E. (1999). "A reapprisal of epeirogenic flexure axes in southern Africa". South African Journal of Geology . 102 (4): 363–376.
- ↑ Eaton, Gordon P., Epeirogeny in the Southern Rocky Mountains region: Evidence and origin, Geosphere; October 2008; v. 4; no. 5; p. 764–784; doi : 10.1130/GES00149.1
- ↑ Japsen, Peter; Green, Paul F.; Bonow, Johan M.; Erlström, Mikael (2016). "Episodic burial and exhumation of the southern Baltic Shield: Epeirogenic uplifts during and after break-up of Pangaea". Gondwana Research . 35: 357–377.