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Glacial Buzzsaw
The glacial buzzsaw is a hypothesis claiming erosion by warm-based glaciers is key to limit the height of mountains above certain threshold altitude. To this the hypothesis adds that great mountain massifs are leveled towards the equilibrium line altitude (ELA), which would act as a “climatic base level”. Starting from the hypothesis it has been predicted that local climate restricts the maximum height that mountain massifs can attain by effect of uplifting tectonic forces. It follows that as local climate is cooler at higher latitudes the highest mountains are lower there compared to the tropics where glaciation is and has been more limited. The mechanism behind the glacial buzzsaw effect would be the erosion of small glaciers that are mostly unable to erode much below the equilibrium line altitude since they do not reach these altitudes because of increased ablation. Instead, large valley glaciers may easily surpass the equilibrium line altitude and do therefore not contrib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypothesis
A hypothesis (: hypotheses) is a proposed explanation for a phenomenon. A scientific hypothesis must be based on observations and make a testable and reproducible prediction about reality, in a process beginning with an educated guess or thought. If a hypothesis is repeatedly independently demonstrated by experiment to be true, it becomes a scientific theory. In colloquial usage, the words "hypothesis" and "theory" are often used interchangeably, but this is incorrect in the context of science. A working hypothesis is a provisionally-accepted hypothesis used for the purpose of pursuing further progress in research. Working hypotheses are frequently discarded, and often proposed with knowledge (and warning) that they are incomplete and thus false, with the intent of moving research in at least somewhat the right direction, especially when scientists are stuck on an issue and brainstorming ideas. A different meaning of the term ''hypothesis'' is used in formal l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, passivation (chemistry), forming a protective layer of aluminium oxide, oxide on the surface when exposed to air. It visually resembles silver, both in its color and in its great ability to reflect light. It is soft, magnetism, nonmagnetic, and ductility, ductile. It has one stable isotope, 27Al, which is highly abundant, making aluminium the abundance of the chemical elements, 12th-most abundant element in the universe. The radioactive decay, radioactivity of aluminium-26, 26Al leads to it being used in radiometric dating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacial Erosion Landforms
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land“Glacier, N., Pronunciation.” Oxford English Dictionary, Oxford UP, June 2024, https://doi.org/10.1093/OED/7553486115. Accessed 25 Jan. 2025. and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on every contine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Truncated Upland
Truncated upland, truncated highland or bevelled upland () are the heavily eroded remains of a fold mountain range, often from an early period in earth history.Murawski, H., Meyer, W. (2004): ''Geologisches Wörterbuch.'' Spektrum Akademischer Verlag, 11th edn., 262 pp. The term ''Rumpfgebirge'' ("rump mountains") was first introduced into the literature in 1886 by Ferdinand von Richthofen. The rumps of the former mountain ranges may be found in many lowland regions of the Earth's crust (where they form the so-called basement rocks) and especially outcrop in Central Europe through more recent tectonics.This could result in an uplifted peneplain which is one type of truncated upland. The valley structures of truncated uplands are often more irregular than in the younger fold mountains, which is due to the considerably younger tectonic processes and stronger erosion (geology), erosion of the former mountain ranges that were originally often up to several thousand metres high. By con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summit Accordance
300px, The highest of hills in this picture show fairly similar heights making up a summit accordance. Aerial photograph from the Altai region of Russia. A summit accordance (sometimes also known by the German loan word gipfelflur) exists when hills and mountaintops, and eventually also plateaux, have such a disposition that they form a geometric plane that may be either horizontal or tilted. Summit accordances can be the vestiges of former continuous erosion surfaces that were uplifted and eroded. Other proposed explanations include: *the possibility that erosion becomes more effective at height, tearing down mountains that stand out *that isostasy regulates the height of individual mountain masses meaning that small mountains might be uplifted and large mountains dragged down *that landscape dissection by uniformly spaced streams eventually reach a state in which summits attain similar heights *that summit accordance is derivative of structural planes exposed by erosion See a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryoplanation
In geomorphology, cryoplanation or is a term used to both describe and explain the formation of plains, terraces and pediments in periglacial environments. Uncertainty surrounds the term, and the effectiveness of the cryoplanation process is held to be limited meaning it can only produce small terraces. Instead, many of so-called cryoplanation terraces are likely an expression of the underlying lithology and rock structure rather than being unique products of cold-climate processes. Cryoplanation can be seen as a variant of pediplanation that is restricted to cold climates. All the cryoplanation surfaces that exist at present date to the Quaternary. History of the concept The existence of flat bedrock surfaces in the mountains of Siberia was noted in the 1930s. Soviet scientists S.G. Boch and I.I. Krasnov first proposed a cyclical model for the formation these surfaces in 1943. This model influenced central and western European geomorphologists. Carl Troll, writing in German, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Climatic Geomorphology
Climatic geomorphology is the study of the role of climate in shaping landforms and the earth-surface processes. An approach used in climatic geomorphology is to study relict landforms to infer ancient climates. Being often concerned about past climates climatic geomorphology considered sometimes to be an aspect of historical geology. Since landscape features in one region might have evolved under climates different from those of the present, studying climatically disparate regions might help understand present-day landscapes. For example, Julius Büdel studied both cold-climate processes in Svalbard and weathering processes in tropical India to understand the origin of the relief of Central Europe, which he argued was a palimpsest of landforms formed at different times and under different climates. Sub-disciplines The various subbranches of climatic geomorphology focus on specific climatic environments. Desert geomorphology Desert geomorphology or the geomorphology of arid an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global And Planetary Change
''Global and Planetary Change'' is a monthly peer-reviewed scientific journal covering research into the earth sciences, particularly pertaining to changes in aspects thereof such as sea level and the chemical composition of the atmosphere. It has been published by Elsevier since it was established in 1989. The editors-in-chief are Alan Haywood, Jed Kaplan, Trude Storelvmo, Liviu Matenco, Zhengtang Guo, Maoyan Zhu, Fabienne Marret-Davies, Howard Falcon-Lang. According to the ''Journal Citation Reports'', the journal has a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact factor values are considered more prestigious or important within their field. The Impact Factor of a journa ... of 5.114. References External links * Earth and atmospheric sciences journals Planetary science journals Academic journals established in 1989 Elsevier academic journals Monthly jour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Greenland
Kitaa, originally Vestgrønland ("West Greenland"), is a former administrative division of Greenland. It was by far the most populated of the divisions, being home to almost 90% of the total population. The divisions were de facto replaced by statistical regions after Greenland received home rule in 1979. It is bordered in the west by the Baffin Bay, Davis Strait, Labrador Sea and the North Atlantic Ocean. To the east lies Tunu. All but three of the island territory's municipalities were located in West Greenland. These were (in geographical order, from south to north): * Nanortalik * Qaqortoq * Narsaq * Ivittuut * Paamiut * Nuuk * Maniitsoq * Sisimiut * Kangaatsiaq * Aasiaat * Qasigiannguit * Ilulissat * Qeqertarsuaq * Uummannaq * Upernavik See also * Subdivisions of ''Norden'' * Administrative divisions of Greenland Greenland is divided into five municipalities and two unincorporated areas. The municipalities are Avannaata, Kujalleq, Qeqertalik, Qeqqata, and S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planation Surface
In geology and geomorphology a planation surface is a large-scale land surface that is almost flat with the possible exception of some residual hills. The processes that form planation surfaces are labelled collectively planation and are exogenic (chiefly erosion). Planation surfaces are planated regardless of bedrock structures. On Earth, they constitute some of the most common landscapes. Geological maps indicate that planation surfaces may comprise 65% of the landscapes on Saturn's largest moon, Titan, which hosts a hydrological cycle of liquid methane. Peneplains and pediplains are types of planation surfaces planated respectively by "peneplanation" and "pediplanation". In addition to these there are planation surfaces proposed to be formed by cryoplanation, marine processes, areal glacial erosion and salt weathering. The term ''planation surface'' is often preferred over others because some more specific planation surface types and processes remain controversial. Etchp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Last Glacial Maximum
The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered much of Northern North America, Northern Europe, and Asia and profoundly affected Earth's climate by causing a major expansion of deserts, along with a large drop in sea levels. Based on changes in position of ice sheet margins dated via cosmogenic nuclide, terrestrial cosmogenic nuclides and radiocarbon dating, growth of ice sheets in the southern hemisphere commenced 33,000 years ago and maximum coverage has been estimated to have occurred sometime between 26,500 years ago and 20,000 years ago. After this, deglaciation caused an abrupt rise in sea level. Decline of the West Antarctica ice sheet occurred between 14,000 and 15,000 years ago, consistent with evidence for another abrupt rise in the sea level about 14,500 years ago. Glacier fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacial Cirque
A (; from the Latin word ) is an amphitheatre-like valley formed by Glacier#Erosion, glacial erosion. Alternative names for this landform are corrie (from , meaning a pot or cauldron) and ; ). A cirque may also be a similarly shaped landform arising from fluvial erosion. The concave shape of a glacial cirque is open on the downhill side, while the cupped section is generally steep. Cliff-like slopes, down which ice and glaciated debris combine and converge, form the three or more higher sides. The floor of the cirque ends up bowl-shaped, as it is the complex convergence zone of combining ice flows from multiple directions and their accompanying rock burdens. Hence, it experiences somewhat greater erosion forces and is most often overdeepening, overdeepened below the level of the cirque's low-side outlet (stage) and its down-slope (backstage) valley. If the cirque is subject to seasonal melting, the floor of the cirque most often forms a tarn (lake), tarn (small lake) behind a d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
