Shield (geology) - Citizendia

Shield Platform Orogen Basin Large igneous province Extended crust

Oceanic crust: 0–20 Ma 20–65 Ma >65 Ma

A shield is generally a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. A geologic or geomorphic province is a spatial entity with common geologic / geomorphic attributes The United States Geological Survey ( USGS) is a scientific agency of the United States government. In geology a platform is a continental area covered by relatively flat or gently tilted mainly Sedimentary strata, which overlie a basement of consolidated Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and A structural basin is a large-scale structural formation of rock strata formed by tectonic warping of previously flat lying strata. Large Igneous provinces (LIPS were originally defined by Coffin and Eldholm (1992 as areas of Earth's surface that contain very large volumes of magmatic rocks (typically In Geology, a crust is the outermost solid shell of a planet or moon Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics. In all cases, the age of these rocks is greater than 570 million years and sometimes dates back 2 to 3. 5 billion years. They have been little affected by tectonic events following the end of the Precambrian Era, and are relatively flat regions where mountain building, faulting, and other tectonic processes are greatly diminished compared with the activity that occurs at the margins of the shields and the boundaries between tectonic plates. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere

The term shield was originally translated from German Schild by H. B. C. Sollas in Eduard Suess's Face of Earth in 1901. Eduard Suess ( August 20, 1831 London &ndash April 26, 1914 Vienna) was a Geologist who was an expert on the

A shield is that part of the continental crust in which these usually Precambrian basement rocks crop out extensively at the surface. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current Basement or Basement Rock music was a sub-genre coined in 2006 in an article by music magazine TGR Shields themselves can be very complex: they consist of vast areas of granitic or granodioritic gneisses, usually of tonalitic composition, and they also contain belts of sedimentary rocks, often surrounded by low-grade volcano-sedimentary sequences, or greenstone belts. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Granodiorite (ˌgrænəˈdaɪəraɪt/ /ˌgreɪn- is an intrusive Igneous rock similar to Granite, but contains more Plagioclase than Potassium feldspar Gneiss (ˈnaɪs is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally Tonalite is an igneous, Plutonic ( Intrusive) rock, of Felsic composition with Phaneritic texture Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Greenstone belts are zones of variably metamorphosed Mafic to Ultramafic Volcanic sequences with associated Sedimentary rocks that These rocks are frequently metamorphosed greenschist, amphibolite, and granulite facies. Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i Greenschist - also known as greenstone - is a general field petrologic term applied to metamorphic and/or altered Mafic Volcanic rock Amphibolite (æmˈfɪbəlaɪt is the name given to a rock consisting mainly of hornblende Amphibole, the use of the term being restricted however to Metamorphic Granulites are fine to medium–grained Metamorphic rocks that have experienced high Temperatures of metamorphism composed mainly of Feldspars sometimes associated The term " Facies " can also refer to distinctive Facial expressions associated with conditions such as Williams syndrome.

Shields are normally the nucleus of continents and most are bordered by belts of folded Cambrian rocks. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Because of their stability, erosion has flattened the topography of most of the continental shields; however, they commonly do have a very gently convex surface. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Topography ( topo-, "place" and graphia, "writing" is the study of Earth 's Surface features or those of Planets They are also surrounded by a sediment covered platform. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of By contrast, in a platform the shield, more accurately referred to then as the crystalline "basement", is overlain by horizontal or subhorizontal sediment. In geology a platform is a continental area covered by relatively flat or gently tilted mainly Sedimentary strata, which overlie a basement of consolidated In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating In Geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover or more generally Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Together, the shield, platform and basement are the parts that comprise the stable interior portion of the continental crust known as the "craton. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived "

The margins surrounding a shield generally constitute relatively mobile zones of intense tectonic or plate-like dynamic mechanisms. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere In these areas, complex sequences of mountain building (orogeny) events have been documented over the past few hundred million years. Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and

For example: the Ural Mountains to the west of the Angaran Shield, and the Himalayas to the south, are the mobile zones that separate the shield from the Baltic Shield to the west and the Indian Shield to the south. Riphean redirects here For the time period see Riphean stage The Ural Mountains (Ура́льские го́ры Uralskiye The Indian Shield is part of the Indian Craton and occupies two-thirds of the southern Indian Peninsula. Shield margins have been subjected to geotectonic forces that have both destroyed and rebuilt the margins and the cratons that they partially comprise. In fact, the growth of continents has occurred as a result of the accretion of younger rocks that underwent deformations during series of mountain building processes. In Materials science, deformation is a change in the shape or size of an object due to an applied force. In a sense, these belts of folded rocks have been welded onto the borders of the preexisting shields, thus increasing the size of the proto-continents that they make up.

Continental shields occur on all continents, for example:

The Canadian Shield forms the nucleus of North America and extends from Lake Superior on the south to the Arctic Islands on the north, and from western Canada eastward across to include most of Greenland. The Canadian Shield &mdash also called the Laurentian Plateau, or Bouclier Canadien (French &mdash is a large geological shield covered by Lake Superior is the largest of the five Great Lakes of North America. The Arctic is the Region around the Earth 's North Pole, opposite the Antarctic region around the South Pole. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the
The Amazonian (Brazilian) Shield on the eastern bulge portion of South America. The Amazonian shield is located in South America and occupies much of the eastern part of the continent South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a Bordering this is the Guiana Shield to the north, and the Platian Shield to the south. The Guiana Shield (Guayana is one of the three Cratons of the South American Plate.
The Baltic (Fennoscandian) Shield is located in eastern Norway, Finland and Sweden. The Baltic Shield (sometimes referred to as the Fennoscandian Shield) is located in Fennoscandia ( Norway, Sweden and Finland) northwest
The African (Ethiopian) Shield is located in Africa. The African Shield, sometimes called the Ethiopian Shield is located on the eastern horn of Africa and extends eastward to western Saudi Arabia and the eastern half of Madagascar
The Australian Shield occupies most of the western half of Australia. Australian Shield, also called the Western Australian Shield or Western Plateau, occupies more than half of the continent of Australia.
The Arabian-Nubian Shield on the western edge of Arabia. The Arabian-Nubian Shield (ANS is an exposure of Precambrian crystalline rocks on the flanks of the Red Sea.
The Antarctic Shield. The East Antarctic craton is an ancient Craton that forms most of Antarctica.
In Asia, an area in China and North Korea is sometimes referred to as the China-Korean Shield. The North China Craton is one of the smaller Continental Cratons of the Earth.
The Angaran Shield, as it is sometimes called, is bounded by the Yenisey River on the west, the Lena River on the east, the Arctic Ocean on the north, and Lake Baikal and south. Siberia is the Craton located in the heart of the region of Siberia.

See also