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Kenorland
Kenorland is a hypothetical Neoarchean supercontinent. If it existed, it would have been one of the earliest known supercontinents on Earth. It is thought to have formed during the Neoarchaean Era c. 2.72 billion years ago (2.72 Ga) by the accretion of Neoarchaean cratons and the formation of new continental crust. It comprised what later became Laurentia (the core of today's North America and Greenland), Baltica (today's Scandinavia and Baltic), Western Australia and Kalaharia. Swarms of volcanic dikes and their paleomagnetic orientation as well as the existence of similar stratigraphic sequences permit this reconstruction. The core of Kenorland, the Baltic/Fennoscandian Shield, traces its origins back to over 3.1 Ga. The Yilgarn craton (present-day Western Australia) contains zircon crystals in its crust that date back to 4.4 Ga. Kenorland was named after the Kenoran orogeny (also called the Algoman orogeny), which in turn was named after the town of Kenora, Ontario. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", which leaves room for interpretation and is easier to apply to Precambrian times. To separate supercontinents from other groupings, a limit has been proposed in which a continent must include at least about 75% of the continental crust then in existence in order to qualify as a supercontinent. Moving under the forces of plate tectonics, supercontinents have assembled and dispersed multiple times in the geologic past. According to modern definitions, a supercontinent does not exist today; the closest is the current Afro-Eurasian landmass, which covers approximately 57% of Earth's total land area. The last period in which the continental landmasses were near to one another was 336 to 175 million years ago, forming the supercontinent Pangaea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neoarchaean
The Neoarchean ( ; also spelled Neoarchaean) is the last geologic era in the Archean Eon that spans from 2800 to 2500 million years ago—the period being defined chronometrically and not referencing a specific level in a rock section on Earth. The era is marked by major developments in complex life and continental formation. Complex life This era saw the rise of oxygen in the atmosphere after oxygenic photosynthesis evolved in cyanobacteria as early as the Mesoarchean era. The environmental changes that occurred in the Neoarchean such as its developing atmospheric and soil compositions drastically differentiated the era from others in its encouragement of microbial metabolisms to evolve and diversify. The era could have also seen pre-biotic organic molecules being brought to Earth through meteorites, comets, or through abiotic reactions. The growth of juvenile continental crust as well as the onset of plate tectonics in the Archean allowed for the colonization of a larger va ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neoarchean
The Neoarchean ( ; also spelled Neoarchaean) is the last geologic era in the Archean Eon that spans from 2800 to 2500 million years ago—the period being defined chronometrically and not referencing a specific level in a rock section on Earth. The era is marked by major developments in complex life and continental formation. Complex life This era saw the rise of oxygen in the atmosphere after oxygenic photosynthesis evolved in cyanobacteria as early as the Mesoarchean era. The environmental changes that occurred in the Neoarchean such as its developing atmospheric and soil compositions drastically differentiated the era from others in its encouragement of microbial metabolisms to evolve and diversify. The era could have also seen pre-biotic organic molecules being brought to Earth through meteorites, comets, or through abiotic reactions. The growth of juvenile continental crust as well as the onset of plate tectonics in the Archean allowed for the colonization of a larger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laurentia
Laurentia or the North American craton is a large continental craton that forms the Geology of North America, 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 belt, orogenic belts. Small microcontinents and oceanic islands collided with and Suture (geology), sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today. Etymology The craton is named after the Laurentian Shield, through the Laurentian Mountains, which received their name from the St. Lawrence River, named after Saint Lawrence of Rome. Interior platform In eastern and centra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Era (geology)
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Kenora
Kenora (), previously named Rat Portage (), is a city situated on the Lake of the Woods in Ontario, Canada, close to the Manitoba boundary, and about east of Winnipeg by road. It is the seat of Kenora District. The history of the name extends beyond the time of French settlers arriving in the region. The name Rat Portage had its origin in the Ojibwe language, Ojibwe name ''Wazhashk-Onigam'', which, roughly translated, means portage to the country of the muskrats. A shortened and somewhat corrupted version, Rat Portage, was adopted by the Hudson's Bay Company in naming their post, then located on Old Fort Island on the Winnipeg River. When the post was moved to the mainland and a town grew up around it, the name Rat Portage was assumed by the community. The town of Rat Portage was renamed in 1905 by using the first two letters of itself and the neighbouring towns of Keewatin and Norman to form the present-day City of Kenora. In 2001, the towns of Kenora (including Norman) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karelia
Karelia (; Karelian language, Karelian and ; , historically Коре́ла, ''Korela'' []; ) is an area in Northern Europe of historical significance for Russia (including the Soviet Union, Soviet era), Finland, and Sweden. It is currently divided between northwestern Russia (the Federal subjects of Russia, federal subjects of the Republic of Karelia and Leningrad Oblast) and Finland (the Regions of Finland, regions of South Karelia, North Karelia, and the eastern portion of Kymenlaakso). Use of name Various regions may be called Karelia. Finnish Karelia is a historical province of Finland and is now divided between Finland and Russia, often called just ''Karjala'' in Finnish. The eastern part of this chiefly Lutheran area was ceded to Russia after the Winter War of 1939–40. The Republic of Karelia is a Russian federal subject, including East Karelia, with a chiefly Russian Orthodox population. Within present-day Finland, ''Karjala'' refers to the Regions of Finland, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoproterozoic
The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further subdivided into four geologic periods, namely the Siderian, Rhyacian, Orosirian and Statherian. Paleontological evidence suggests that the Earth's rotational rate ~1.8 billion years ago equated to 20-hour days, implying a total of ~450 days per year. It was during this era that the continents first stabilized. Atmosphere The Earth's atmosphere was originally a weakly reducing atmosphere consisting largely of nitrogen, methane, ammonia, carbon dioxide and inert gases, in total comparable to Titan's atmosphere. When oxygenic photosynthesis evolved in cyanobacteria during the Mesoarchean, the increasing amount of byproduct dioxygen began to deplete the reductants in the ocean, land surface and the atmosphere. Eventually all surf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rift
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals and volcanic gas, gas bubbles. Magma is produced by melting of the mantle (geology), mantle or the Crust (geology), crust in various tectonics, tectonic settings, which on Earth include subduction zones, continental rift (geology), rift zones, mid-ocean ridges and Hotspot (geology), hotspots. Mantle and crustal melts migrate upwards through the crust where they are thought to be stored in magma chambers or trans-crustal crystal mush, crystal-rich mush zones. During magma's storage in the crust, its composition may be modified by Fractional crystallization (geology), fractional crystallization, contaminati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latitude
In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at the south pole to 90° at the north pole, with 0° at the Equator. Parallel (latitude), Lines of constant latitude, or ''parallels'', run east-west as circles parallel to the equator. Latitude and longitude are used together as a coordinate pair to specify a location on the surface of the Earth. On its own, the term "latitude" normally refers to the ''geodetic latitude'' as defined below. Briefly, the geodetic latitude of a point is the angle formed between the vector perpendicular (or ''Normal (geometry), normal'') to the ellipsoidal surface from the point, and the equatorial plane, plane of the equator. Background Two levels of abstraction are employed in the definitions of latitude and longitude. In the first step the physical surface i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
