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Orogeny is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An orogenic belt or orogen develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere. A synorogenic process or event is one that occurs during an orogeny.
Obduction is a geological process whereby denser oceanic crust is scraped off a descending ocean plate at a convergent plate boundary and thrust on top of an adjacent plate. When oceanic and continental plates converge, normally the denser oceanic crust sinks under the continental crust in the process of subduction. Obduction, which is less common, normally occurs in plate collisions at orogenic belts or back-arc basins.
The geology of the Appalachians dates back more than 1.2 billion years to the Mesoproterozoic era when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the development of the range during the formation of Pangea. The rocks exposed in today's Appalachian Mountains reveal elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks, and slivers of ancient ocean floor—strong evidences that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of Pangea with the Appalachians and neighboring Anti-Atlas mountains near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.
The Iapetus Ocean existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale. It lay in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between Western Gondwana and Laurentia.
Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, is more than three billion years old and formed part of the Rodinia supercontinent at c. 1 Ga.
The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), with deformational, plutonic, and metamorphic events extending into the early Mississippian. The Acadian orogeny is the third of the four orogenies that formed the Appalachian Mountains and subsequent basin. The preceding orogenies consisted of the Grenville and Taconic orogenies, which followed a rift/drift stage in the Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogeny extended from the Canadian Maritime provinces migrating in a southwesterly direction toward Alabama. However, the northern Appalachian region, from New England northeastward into Gaspé region of Canada, was the most greatly affected region by the collision.
The Taconic orogeny was a mountain building period that ended 440 million years ago (Ma) and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the east coast of the United States. As the mountain chain eroded in the Silurian and Devonian periods, sediment spread throughout the present-day Appalachians and midcontinental North America.
The Caledonian orogeny was a mountain-building cycle recorded in the northern parts of the British Isles, the Scandinavian Caledonides, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the Laurentia and Baltica continents and the Avalonia microcontinent collided.
The Variscan or Hercynianorogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea.
The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland.
The geology of Norway encompasses the history of Earth that can be interpreted by rock types found in Norway, and the associated sedimentological history of soils and rock types.
Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and the Hebridean Terrane in northwest Scotland. During other times in its past, Laurentia has been part of larger continents and supercontinents and consists of many smaller terranes assembled on a network of early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.
The Iapetus Suture is one of several major geological faults caused by the collision of several ancient land masses forming a suture. It represents in part the remains of what was once the Iapetus Ocean. Iapetus was the father of Atlas in Greek mythology, making his an appropriate name for what used to be called the 'Proto-Atlantic Ocean'. When the Atlantic Ocean opened, in the Cretaceous period, it took a slightly different line from that of the Iapetus suture, with some originally Laurentian rocks being left behind in north-west Europe and other, Avalonian, rocks remaining as part of Newfoundland.
The geology of Massachusetts includes numerous units of volcanic, intrusive igneous, metamorphic and sedimentary rocks formed within the last 1.2 billion years. The oldest formations are gneiss rocks in the Berkshires, which were metamorphosed from older rocks during the Proterozoic Grenville orogeny as the proto-North American continent Laurentia collided against proto-South America. Throughout the Paleozoic, overlapping the rapid diversification of multi-cellular life, a series of six island arcs collided with the Laurentian continental margin. Also termed continental terranes, these sections of continental rock typically formed offshore or onshore of the proto-African continent Gondwana and in many cases had experienced volcanic events and faulting before joining the Laurentian continent. These sequential collisions metamorphosed new rocks from sediments, created uplands and faults and resulted in widespread volcanic activity. Simultaneously, the collisions raised the Appalachian Mountains to the height of the current day Himalayas.
The Scandinavian Caledonides are the vestiges of an ancient, today deeply eroded orogenic belt formed during the Silurian–Devonian continental collision of Baltica and Laurentia, which is referred to as the Scandian phase of the Caledonian orogeny. The size of the Scandinavian Caledonides at the time of their formation can be compared with the size of the Himalayas. The area east of the Scandinavian Caledonides, including parts of Finland, developed into a foreland basin where old rocks and surfaces were covered by sediments. Today, the Scandinavian Caledonides underlay most of the western and northern Scandinavian Peninsula, whereas other parts of the Caledonides can be traced into West and Central Europe as well as parts of Greenland and eastern North America.
The Durness Group is a geological group, a carbonate-dominated stratigraphic unit that forms a c. 170 km long narrow and discontinuous outcrop belt along the north-western coast of Scotland from the Isle of Skye and Loch Kishorn in the south to Durness and Loch Eriboll in the north. It forms the youngest part of the foreland basin of the Moine Thrust Belt in the Scottish Northwest Highlands and is incorporated into this belt's lowermost thrust sheets, where it is often affected by thrust faulting. It overlies the Ardvreck Group.
The geology of Sweden is the regional study of rocks, minerals, tectonics, natural resources and groundwater in the country. The oldest rocks in Sweden date to more than 2.5 billion years ago in the Precambrian. Complex orogeny mountain building events and other tectonic occurrences built up extensive metamorphic crystalline basement rock that often contains valuable metal deposits throughout much of the country. Metamorphism continued into the Paleozoic after the Snowball Earth glaciation as the continent Baltica collided with an island arc and then the continent Laurentia. Sedimentary rocks are most common in southern Sweden with thick sequences from the last 250 million years underlying Malmö and older marine sedimentary rocks forming the surface of Gotland.
The geology of national parks in Britain strongly influences the landscape character of each of the fifteen such areas which have been designated. There are ten national parks in England, three in Wales and two in Scotland. Ten of these were established in England and Wales in the 1950s under the provisions of the National Parks and Access to the Countryside Act 1949. With one exception, all of these first ten, together with the two Scottish parks were centred on upland or coastal areas formed from Palaeozoic rocks. The exception is the North York Moors National Park which is formed from sedimentary rocks of Jurassic age.
The Highland Border Ophiolite (HBO) is a set of rocks that are ophiolitic in character found within the Highland Border Complex. They are exposed in a series of fault-bounded outcrops along the line of the Highland Boundary Fault that forms the southeastern boundary to the Grampian Highlands in Scotland. They represent fragments of a piece of oceanic crust or exhumed mantle that has been obducted onto continental crust. These rocks provide an important constraint on models of how the current geometry arose during the Caledonian Orogeny.