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Mount Wrangell
Mount Wrangell, in Ahtna K’ełt’aeni or K’ełedi when erupting, is a massive shield volcano located in Wrangell-St. Elias National Park and Preserve in southeastern Alaska, United States. The shield rises over above the Copper River to its southwest. Its volume is over , making it more than twice as massive as Mount Shasta in California, the largest stratovolcano by volume in the Cascades. It is part of the Wrangell Volcanic Field, which extends for more than across Southcentral Alaska into the Yukon Territory in Canada, and has an eruptive history spanning the time from Pleistocene to Holocene. Description Modern Mount Wrangell, built upon the remnants of a mid-Pleistocene volcano, has an eruptive history spanning from 750,000 years ago to minor phreatic eruptions in 1884.Volcanoes of North America, Wood and Kienle The shield volcano features an ice-filled caldera in diameter at the top of Wrangell's broad summit. The caldera was apparently formed by subsidence rathe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferdinand Von Wrangel
Baron Ferdinand Friedrich Georg Ludwig von Wrangel (russian: Барон Фердина́нд Петро́вич Вра́нгель, tr. ; – ) was a Baltic German explorer and seaman in the Imperial Russian Navy, Honorable Member of the Saint Petersburg Academy of Sciences, a founder of the Russian Geographic Society. He is best known as chief manager of the Russian-American Company, in fact governor of the Russian settlements in present-day Alaska. In English texts, ''Wrangel'' is sometimes spelled ''Vrangel'', a transliteration from Russian, which more closely represents its pronunciation in German, or ''Wrangell''. Biography Wrangel was born in Pskov, into the noble Baltic German Wrangel family and was a distant nephew of Generalfeldmarschall Friedrich von Wrangel. He graduated from the Naval Cadets College in 1815. He participated in Vasily Golovnin's world cruise on the ship ''Kamchatka'' in 1817–1819 and belonged to the cohort of Baltic-German navigators who were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratovolcano
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as . Stratovolcanoes are sometimes called composite volcanoes because of their composite stratified structure, built up from sequential outpourings of erupted materials. They are among the most common types of volcanoes, in contrast to the less common shield volca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nabesna River
The Nabesna River (''Naambia Niign'' in Upper Tanana) is a tributary of the Tanana River in the U.S. state of Alaska. Beginning at Nabesna Glacier in the Alaska Range, it flows north-northeast from Wrangell–St. Elias National Park and Preserve to join the Chisana River near Northway Junction. The combined rivers form the Tanana. Boating The Nabesna River, swift-flowing in its upper reaches, passes through a deep valley that opens into broad plain. Gradually slowing, the river enters the Tetlin National Wildlife Refuge, a region of marshes, hills, lakes, and forests of spruce and birch. The river, suited to running by rafts, hard-shelled kayaks, or decked canoes, is rated Class I (easy) to Class II (medium) on the International Scale of River Difficulty. The current is swift on the stream's upper and slow from there to the mouth. Dangers include cold, swift, silty water, and braided channels. Glacier melt may cause flow rates to rise significantly between morning and afternoo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nabesna Glacier
Nabesna Glacier is a glacier in the U.S. state of Alaska. Fed by deep snowfall in the Wrangell Mountains, the 53 mile (85 km) long Nabesna is the longest valley glacier in North America and the world's longest interior valley glacier. The glacier flows from an extensive icefield which covers the northern flanks of Mount Wrangell, a large shield volcano. It heads initially east past other volcanic peaks including Mount Blackburn and Atna Peaks and then turns north to its terminus near 3,000 ft (900 m) elevation, about south of the old mining settlement of Nabesna at the end of the Nabesna Road. The vast expanse and length of the Nabesna is fed by approximately 40 tributary glaciers. Melting ice at its terminus forms the Nabesna River, which flows northward through Tetlin National Wildlife Refuge and into the Tanana River. Geography The glacier was named for the Nabesna River in 1902 by F. C. Schrader of the U.S. Geological Survey. It provides the normal route of acces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Field
An ice field (also spelled icefield) is a mass of interconnected valley glaciers (also called mountain glaciers or alpine glaciers) on a mountain mass with protruding rock ridges or summits. They are often found in the colder climates and higher altitudes of the world where there is sufficient precipitation for them to form. The higher peaks of the underlying mountain rock that protrude through the icefields are known as nunataks. Ice fields are larger than alpine glaciers, but smaller than ice caps and ice sheets. The topography of ice fields is determined by the shape of the surrounding landforms, while ice caps have their own forms overriding underlying shapes. Formation Ice fields are formed by a large accumulation of snow which, through years of compression and freezing, turns into ice. Due to ice's susceptibility to gravity, ice fields usually form over large areas that are basins or atop plateaus, thus allowing a continuum of ice to form over the landscape uninterrupted b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fumarole
A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcanic activity, but fumarole activity can also precede a volcanic eruption and has been used for eruption prediction. Most fumaroles die down within a few days or weeks of the end of an eruption, but a few are persistent, lasting for decades or longer. An area containing fumaroles is known as a fumarole field. The predominant vapor emitted by fumaroles is steam, formed by the circulation of groundwater through heated rock. This is typically accompanied by volcanic gases given off by magma cooling deep below the surface. These volcanic gases include sulfur compounds, such as various sulfur oxides and hydrogen sulfide, and sometimes hydrogen chloride, hydrogen fluoride, and other gases. A fumarole that emits significant sulfur compounds is some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope movement. Processes that lead to subsidence include dissolution of underlying carbonate rock by groundwater; gradual compaction of sediments; withdrawal of fluid lava from beneath a solidified crust of rock; mining; pumping of subsurface fluids, such as groundwater or petroleum; or warping of the Earth's crust by tectonic forces. Subsidence resulting from tectonic deformation of the crust is known as tectonic subsidence and can create accommodation for sediments to accumulate and eventually lithify into sedimentary rock. Ground subsidence is of global concern to geologists, geotechnical engineers, surveyors, engineers, urban planners, landowners, and the public in general.National Research Council, 1991. ''Mitigating losses from land subsi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is gone. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a Volcanic crater, crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur each century, the formation of a caldera is a rare event, occurring only a few times per century. Only seven caldera-forming collapses are known to have occurred between 1911 and 2016. More recently, a caldera collapse occurred at Kīlauea, Hawaii in 2018. Etymology The term ''caldera'' comes from Spanish language, S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phreatic Eruption
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano. Phreatic eruptions typically include steam and rock fragments; the inclusion of liquid lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten magma is included, volcanologists classify the event as a phreatomagmatic eruption. These eruptions occasionally create broad, low-relief craters called '' maars''. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas-emissions. Carbon dioxide c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by total area. Its southern and western border with the United States, stretching , is the world's longest binational land border. Canada's capital is Ottawa, and its three largest metropolitan areas are Toronto, Montreal, and Vancouver. Indigenous peoples have continuously inhabited what is now Canada for thousands of years. Beginning in the 16th century, British and French expeditions explored and later settled along the Atlantic coast. As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces. This began an accretion of provinces an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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