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Algoman Orogeny
The Algoman orogeny, known as the Kenoran orogeny in Canada, was an episode of mountain-building (orogeny) during the Late Archean Eon that involved repeated episodes of continental collisions, compressions and subductions. The Superior province and the Minnesota River Valley terrane collided about 2,700 to 2,500 million years ago. The collision folded the Earth's crust and produced enough heat and pressure to metamorphose the rock. Blocks were added to the Superior province along a boundary that stretches from present-day eastern South Dakota into the Lake Huron area. The Algoman orogeny brought the Archean Eon to a close, about ; it lasted less than 100 million years and marks a major change in the development of the Earth's crust. The Canadian shield contains belts of metavolcanic and metasedimentary rocks formed by the action of metamorphism on volcanic and sedimentary rock. The areas between individual belts consist of granites or granitic gneisses that form fault zones ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Orogenic Wedge
Orogeny () is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An or 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 ( crust and uppermost mantle). A synorogenic (or synkinematic) process or event is one that occurs during an orogeny. The word ''orogeny'' comes . Although it was used before him, the American geologist G. K. Gilbert used the term in 1890 to mean the process of mountain-building, as distinguished from epeirogeny. Tectonics Orogeny takes place on the convergent margin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Craton
A craton ( , , or ; from "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 extending 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 surface, and a '' platform'' which o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Great Lakes Tectonic Zone
The Great Lakes tectonic zone (GLTZ) is bounded by South Dakota at its tip and heads northeast to south of Duluth, Minnesota, then heads east through northern Wisconsin, Marquette, Michigan, and then trends more northeasterly to skim the northernmost shores of lakes. Algoman orogeny added landmass to the Superior province by volcanic activity and continental collision along a boundary that stretches from present-day South Dakota, U.S., into the Lake Huron region near Sudbury, Ontario, Canada. It is long, and separates the older Archean gneissic terrane to the south from younger Late Archean greenstone-granite terrane to the north. The zone is characterized by active compression during the Algoman orogeny (about ), a pulling-apart ( extensional) tectonics (2,450 to 2,100 million years ago), a second compression during the Penokean orogeny (1,900 to 1,850 million years ago), a second extension during Middle Proterozoic time (1,600 million years ago) and minor reactivation during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Kewaunee County, Wisconsin
Kewaunee County is a county located in the U.S. state of Wisconsin. As of the 2020 census, the population was 20,563. Its county seat is Kewaunee. The county was created in 1852 and organized in 1859. Its Menominee name is ''Kewāneh'', an archaic name for a species of duck. Kewaunee County is part of the Green Bay, WI Metropolitan Statistical Area as well as the Green Bay- Shawano, WI Combined Statistical Area. Uniquely in Wisconsin, the county is considered both a high-farming concentration county and a high-manufacturing county by the U.S. Department of Agriculture, meaning at least 20 percent of its earnings came from agriculture and at least 25 percent came from manufacturing. Fishing and boating In 2018, Kewaunee County ranked first in the state in the Chinook salmon harvest, with 26,557 fish caught, with nearby Door County ranking second at 14,268 fish caught. Chinook salmon are sought after by tourists enjoying chartered fishing trips. The state record rainbow tro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Algoma, Wisconsin
Algoma ( ) is a city in Kewaunee County, Wisconsin, United States. The population was 3,243 at the 2020 United States census, 2020 census. Algoma is part of the Green Bay metropolitan area. History The Ahnapee settlement, which eventually became known as Algoma, was founded in 1834 by Joseph McCormick of Manitowoc, Wisconsin, Manitowoc. In 1851, Ireland, Irish and England, English pioneers moved to the area and called the place ''Wolf River''. The wolf was a legendary animal in stories told by the local Potawatomi Indians. (This animal eventually became the mascot of the Algoma School District, Algoma High School.) In the Menominee language, the town is known as , meaning "snowshoe". In the mid-19th century, immigrants from Germany, Bohemia, Scandinavia, and Belgium settled in the community. The earliest businesses consisted of a sawmill, a general store, and churches. In 1859, the name of the town was changed from Wolf to ''Ahnapee'' a corruption (linguistics), corruption of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gneiss
Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under pressures ranging from 2 to 15 kbar, sometimes even more, and temperatures over 300 °C (572 °F). Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct Cleavage (geology), cleavage. Gneisses are common in the ancient crust of Continental Shield, continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description image:Orthogneiss Geopark.jpg, Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct Cleavage (geology), cleavage. In other words, it i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Superior Craton
The Superior Craton is a stable fault block, crustal block covering Quebec, Ontario, and southeast Manitoba in Canada, and northern Minnesota in the United States. It is the biggest craton among those formed during the Archean period. A craton is a large part of the Earth's Crust (geology), crust that has been stable and subjected to very little geological changes over a long time. The size of Superior Craton is about 1,572,000 km2. The craton underwent a series of events from 4.3 to 2.57 Year#SI prefix multipliers, Ga. These events included the growth, drifting and deformation of both Oceanic crust, oceanic and continental crusts. Researchers have divided the Superior Craton into many different domains based on rock types and deformation styles. These domains (grouped into western and eastern superior provinces), include the North Superior Superterrane and Wawa Terrane, among others (shown in the table below). Studies on the formation of the Superior Craton varied in progress ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Canadian Shield
The Canadian Shield ( ), also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the ancient geologic core of the North American continent. Glaciation has left the area with only a thin layer of soil, through which exposures of igneous bedrock resulting from its long volcanic history are frequently visible. As a deep, common, joined bedrock region in eastern and central Canada, the shield stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada and most of Greenland; it also extends south into the northern reaches of the continental United States. Geographical extent The Canadian Shield is a physiographic division comprising four smaller physiographic provinces: the Laurentian Upland, Kazan Region, Davis and James. The shield extends into the United States as the Adirondack Mountains ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Greenstone Belts
Greenstone belts are zones of variably Metamorphism, metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archean, Archaean and Proterozoic cratons between granite and gneiss bodies. The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks: The typical green minerals are Chlorite group, chlorite, actinolite, and other green amphiboles. Greenstone belts also often contain ore deposits of gold, silver, copper, zinc, and lead. A greenstone belt is typically several dozens to several thousand kilometres long. Typically, a greenstone belt within the greater volume of otherwise homogeneous granite-gneiss within a craton contains a significantly larger degree of heterogeneity and complications and forms a tectonic marker far more distinct than the much more voluminous and homogeneous granites. Additionally, a greenstone belt contains far more information on tectonic and Metamorphism, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Terranes
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from the surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault. A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation. An igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a stitching pluton. There is also an older usage of the term ''terrane'', which described a series of related rock formations or an area with a preponderance of a particular rock or rock group. Overview A tectonostratigraphic terrane did not necessarily originate as an independent microplate, since it may not contai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Shield (geology)
A shield is a large area of exposed Precambrian Crystallinity, crystalline igneous rock, igneous and high-grade metamorphic rock, metamorphic rocks that form tectonics, tectonically stable areas. These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years. They have been little affected by tectonic events following the end of the Precambrian, and are relatively flat regions where mountain building, faulting, and other tectonic processes are minor, compared with the activity at their margins and between tectonic plates. Shields occur on all continents. Terminology The term shield cannot be used interchangeably with the term craton. However, shield can be used interchangeably with the term basement (geology), basement. The difference is that a craton describes a basement overlain by a sedimentary rock, sedimentary platform (geology), platform while shield only describes the basement. The term ''shield'', used to describe this type of ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Precambrian
The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinized name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
