Mount Edziza Volcanic Complex
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Mount Edziza Volcanic Complex
The Mount Edziza volcanic complex ( ; abbreviated MEVC) is a group of volcanoes and associated lava flows in northwestern British Columbia, Canada. Located on the Tahltan Highland, it is southeast of Telegraph Creek and southwest of Dease Lake. The complex encompasses a broad, steep-sided lava plateau that extends over . Its highest summit is in elevation, making the MEVC the highest of four large complexes in an extensive north–south trending volcanic region. It is obscured by an ice cap characterized by several Glacier morphology#Outlet glaciers, outlet glaciers that stretch out to lower altitudes. The MEVC consists of several types of volcanoes, including stratovolcanoes, shield volcanoes, cinder cones and lava domes. These volcanoes have formed over the last 7.5 million years during five cycles of magmatic activity which spanned four geologic epochs. Volcanic eruptions during these magmatic cycles produced a wide variety of volcanic rocks that comprise 13 geol ...
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Big Raven Plateau
The Big Raven Plateau is an intermontane plateau in Cassiar Land District of northwestern British Columbia, Canada. It lies on the Tahltan Highland and is surrounded by several valleys, including those of Mess Creek, Kakiddi Creek, Chakima Creek, Walkout Creek and the Klastline River. The plateau is drained by many small streams that flow into these neighbouring valleys and, unlike the valleys, it is relatively barren vegetation, barren of vegetation. Stream erosion has resulted in the creation of canyons with intervening ridges on the eastern and western sides of the plateau, resulting in the creation of rugged terrain. The plateau is in Mount Edziza Provincial Park which is one of the largest provincial parks in British Columbia. Access to the Big Raven Plateau is mainly by aircraft or by a network of horse trails from surrounding roads. The Big Raven Plateau is volcanic plateau, volcanic in origin, consisting mostly of basaltic lava flows of the Mount Edziza volcanic complex t ...
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Trachyte
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanite, aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrusions) enriched with silica and alkali metals. It is the volcanic equivalent of syenite. Trachyte is common wherever alkali magma is erupted, including in late stages of ocean island volcanismMacDonald 1983, pp. 51–52 and in continental rift valleys, above mantle plumes,Philpotts and Ague 2009, pp. 390–394 and in areas of back-arc extension. Trachyte has also been found in Gale crater on Mars. Trachyte has been used as decorative building stone and was extensively used as dimension stone in the Roman Empire and the Republic of Venice. Chemical composition Trachyte has a silica content of 60 to 65% and an alkali oxide content of over 7%. This gives it less SiO2 than rhyolite and more (Na2O plus K2O) than dacite. These chemical differe ...
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Glacier Morphology
Glacier morphology, or the form a glacier takes, is influenced by temperature, precipitation, topography, and other factors. The goal of glacial morphology is to gain a better understanding of glaciated landscapes and the way they are shaped. Types of glaciers can range from massive ice sheets, such as the Greenland ice sheet, to small cirque glaciers found perched on mountain tops. Glaciers can be grouped into two main categories: * Ice flow is constrained by the underlying bedrock topography * Ice flow is unrestricted by surrounding topography Unconstrained Glaciers Ice sheets and ice caps Ice sheets and ice caps cover the largest areas of land in comparison to other glaciers, and their ice is unconstrained by the underlying topography. They are the largest glacial ice formations and hold the vast majority of the world's fresh water. Ice sheets Ice sheets are the largest form of glacial formation. They are continent-sized ice masses that span areas over . They are dome ...
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Ice Cap
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topographical features (i.e., they must lie over the top of mountains). By contrast, ice masses of similar size that ''are'' constrained by topographical features are known as ice fields. The ''dome'' of an ice cap is usually centred on the highest point of a massif. Ice flows away from this high point (the ice divide) towards the ice cap's periphery. Ice caps significantly affect the geomorphology of the area they occupy. Plastic moulding, gouging and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. The Antarctic and Greenland contain 99% of the ice volume on earth, ...
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Summit
A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. The topographic terms acme, apex, peak (mountain peak), and zenith are synonymous. The term (mountain top) is generally used only for a mountain peak that is located at some distance from the nearest point of higher elevation. For example, a big, massive rock next to the main summit of a mountain is not considered a summit. Summits near a higher peak, with some prominence or isolation, but not reaching a certain cutoff value for the quantities, are often considered ''subsummits'' (or ''subpeaks'') of the higher peak, and are considered part of the same mountain. A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top. For summits that are permanently covered in significant layers of ice, the height may be measured by the highest point of rock (rock height) or the highest point of permanent solid ice (snow height). The highest summit in the wo ...
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Lava Plateau
A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava plateaus and pyroclastic plateaus. Lava plateau Lava plateaus are formed by highly fluid basaltic lava during numerous successive eruptions through numerous vents without violent explosions (quiet eruptions). These eruptions are quiet because of the low viscosity of the lava and the small amount of trapped gases. The resulting sheet lava flows may be extruded from linear fissures or rifts or gigantic volcanic eruptions through multiple vents characteristic of the prehistoric era which produced giant flood basalts. Multiple successive and extensive lava flows cover the original landscape to eventually form a plateau, which may contain lava fields, cinder cones, shield volcanoes and other volcanic landforms. In some cases, a lava plateau may be part of a single volcano. An example is the massive Level Mountain shield volcano in northern British Columbia, Canada, which covers an area ...
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Dease Lake
Dease Lake is a small community in the Cassiar Country of the Northern Interior of British Columbia, Canada. It is 230 km south of the Yukon border on Stewart–Cassiar Highway (Highway 37) at the south end of the lake of the same name. Dease Lake is the last major centre before the Alaska Highway while driving northbound, and also the junction to Telegraph Creek and the Grand Canyon of the Stikine. Dease Lake Indian Reserve No. 9 is nearby and is under the governance of the Tahltan First Nation band government. The town sits astride a drainage divide separating the basins of the Dease River (to the north) from that of the Tanzilla (to the south), a tributary of the Stikine. As this is a division point between drainage to the Pacific Ocean, via the Stikine, and the Arctic Ocean, via the Liard and Mackenzie Rivers, this is part of the Continental Divide. The town has a school, various stores, a fuel and service station, hotel, and a Northern Lights College camp ...
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Telegraph Creek
Telegraph Creek is a small community located off Highway 37 in northern British Columbia at the confluence of the Stikine River and Telegraph Creek. The only permanent settlement on the Stikine River, it is home to approximately 250 members of Tahltan First Nation and non-native residents. The town offers basic services, including Anglican and Catholic churches, a general store, a post office, a clinic with several nurses on-call around the clock, two Royal Canadian Mounted Police officers, and a K-9 school. Steep river banks and rocky gorges form the terraced nature of the geography. The community includes Telegraph Creek Indian Reserve No. 6, Telegraph Creek Indian Reserve No. 6A, and Guhthe Tah Indian Reserve No. 12 which are under the governance of the Tahltan First Nation of Telegraph Creek. Stikine Indian Reserve No. 7, which is one mile west (downstream) and on the opposite side of the Stikine River, is under the governance of the Iskut First Nation of the settlement ...
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Lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fracture in the Crust (geology), crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is often also called ''lava''. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing. Etymology The word ''lava'' comes from Ital ...
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Volcano
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually non-explosive whereas those resulting from convergent tectonic activity cause violent eruptions."Mid-ocean ridge tectonics, volcanism and geomorphology." Geology 26, no. 455 (2001): 458. https://macdonald.faculty.geol.ucsb.edu/papers/Macdonald%20Mid-Ocean%20Ridge%20Tectonics.pdf Volcanoes can also form where there is str ...
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Northern Cordilleran Volcanic Province
The Northern Cordilleran Volcanic Province (NCVP), formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America. This belt of volcanoes extends roughly north-northwest from northwestern British Columbia and the Alaska Panhandle through Yukon to the Southeast Fairbanks Census Area of far eastern Alaska, in a corridor hundreds of kilometres wide. It is the most recently defined volcanic province in the Western Cordillera. It has formed due to extensional cracking of the North American continent—similar to other on-land extensional volcanic zones, including the Basin and Range Province and the East African Rift. Although taking its name from the Western Cordillera, this term is a geologic grouping rather than a geographic one. The southmost part of the NCVP has more, and larger, volcanoes than does the rest of the NCVP; further north it is less clearly delineated, describin ...
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Benmoreite
Benmoreite is a volcanic rock of intermediate composition. It is a silica-undersaturated sodium-rich variety of trachyandesite (the other kind is latite) and belongs to the alkaline suite of igneous rocks. It was named after Ben More, a mountain on the Isle of Mull, Scotland. Benmoreite has been found, for example, on Ascension Island and Easter Island, at Mount Berlin in Antarctica, and in Atakor volcanic field, Algeria. Benmoreite lava was erupted during the 2010 eruptions of Eyjafjallajökull. An origin by fractionation from basanite through nepheline hawaiite to nepheline benmoreite has been demonstrated for a volcanic suite in the McMurdo Volcanic Group of late Cenozoic age in McMurdo Sound area of Antarctica. Nepheline benmoreite magmas derived from mantle sources, containing lherzolite xenoliths, display similarities to some plutonic nepheline syenite Nepheline syenite is a holocrystalline Intrusion, plutonic rock that consists largely of nepheline and alkal ...
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