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Aeolian Landform
Aeolian landforms, or Eolian landforms, are produced by either the erosion, erosive or deposition (geology), depositive aeolian processes, action of wind. These features may be built up from sand or snow, or eroded into rock, snow, or ice. Aeolian landforms are commonly observed in sandy deserts and on frozen lakes or sea ice and have been observed and studied around Earth and on other planets, including Mars and Pluto. Terminology The word "aeolian" derives from Aeolus, Æolus, the Greek god of the winds, and the son of Hellen and the nymph Orseis, and a brother of Dorus, Xuthus and Amphictyon. Mechanisms Aeolian landforms are formed when wind Sediment transport, moves sediment (see aeolian processes). Sediment particles move when they are lifted by upwards Bernoulli effect, Bernoulli forces that exceed their downwards weight or when they are dragged from their initial position. Depending on the balance of these forces, particles may either creep (roll) across the surface until ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, transports it to another location where it is deposit (geology), deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by Solvation, dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and Wind wave, waves; glacier, glacial Plucking (glaciation), plucking, Abrasion (geology), abrasion, and scour; areal flooding; Aeolian processes, wind abrasion; groundwater processes; and Mass wastin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orseis
In Greek mythology, Orseïs (; Ancient Greek: Ὀρσηΐς, derived from ὄρσω - ''orsô'', "to rouse, stir, awaken, excite or arise") was the water-nymph (Naiad) of a spring in Thessalia, Greece, and the mythical ancestor of the Greeks. According to M. L. West, her name may have been corrupt for "Othryis", who he suggests was a nymph of Mount Othrys. According to the ''Library'', Orseis married Hellen, son of Deucalion and Pyrrha and brother of Pandora, the legendary eponymous ancestor of the Greeks. Their sons, Dorus, Xuthus, and Aeolus, according to Hesiod's ''Eoiae'' or ''Catalogue of Women'' together with the sons of Pandora, Graecus, Magnetas and Makedon with Zeus, became the founders of the seven primordial tribes of Hellas ( Graecians, Magnetes, Makedones, Dorians, Achaeans, Ionians, and Aeolians). In some accounts, Xenopatra was also called the daughter of Hellen and Orseis. Hellanicus in scholia on Plato, ''Symposium'', 208 (p. 376) Notes References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ripple Marks
In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water ( current or waves) or directly by wind. Defining ripple cross-laminae and asymmetric ripples * ''Current ripple marks'', ''unidirectional ripples'', or ''asymmetrical ripple marks'' are asymmetrical in profile, with a gentle up-current slope and a steeper down-current slope. The down-current slope is the angle of repose, which depends on the shape of the sediment. These commonly form in fluvial and aeolian depositional environments, and are a signifier of the lower part of the Lower Flow Regime. * Ripple cross-laminae forms when deposition takes place during migration of current or wave ripples. A series of cross-laminae are produced by superimposing migrating ripples. The ripples form lateral to one another, such that the crests of vertically succeeding laminae are out of phase and appear to be advancing upslope. This process results in cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barchan
A barchan or barkhan dune (from Kazakh бархан ) is a crescent-shaped dune. Russian naturalist Alexander von Middendorf introduced the term in 1881, working from the occurrence of barchans in Turkestan and in other inland desert regions. Barchans "face" the wind, appearing convex, and are produced by wind action predominantly from one direction. They are a very common landform in sandy deserts all over the world and are arc-shaped, markedly asymmetrical in cross section, with a gentle slope facing toward the wind sand ridge, comprising well-sorted sand. This type of dune possesses two "horns" that face downwind, with the steeper slope known as the slip face, facing away from the wind, downwind, at the angle of repose of the sand in question, approximately 30–35 degrees for medium-fine dry sand. The upwind side is packed by the wind, and stands at about 15 degrees. Barchans may be high and wide at the base measured perpendicular to the wind. Simple barchan dune ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dunes
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat regions covered with wind-swept sand or dunes, with little or no vegetation, are called '' ergs'' or ''sand seas''. Dunes occur in different shapes and sizes, but most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter ''slip face'' in the lee side. The valley or trough between dunes is called a ''dune slack''. Dunes are most common in desert environments, where the lack of moisture hinders the growth of vegetation that would otherwise interfere with the development of dunes. However, sand deposits are not restricted to deserts, and dunes are also found along sea shores, along streams in semiarid climates, in areas of glacial outwash, and in other areas where poorly cemented sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Sand Dunes National Park And Preserve
Great Sand Dunes National Park and Preserve is a national park of the United States that conserves an area of large sand dunes on the eastern edge of the San Luis Valley, and an adjacent national preserve in the Sangre de Cristo Range, in south-central Colorado. The park was originally designated Great Sand Dunes National Monument on March 17, 1932, by President Herbert Hoover. The original boundaries protected an area of ."Antiquities Act 1906-2006: Maps, facts and figures" . ''nps.gov''. National Park Service. Retrieved December 12, 2017. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saltation (geology)
In geology, saltation () is a specific type of particle transport by fluids such as wind or water. It occurs when loose materials are removed from a bed and carried by the fluid, before being transported back to the surface. Examples include pebble transport by rivers, sand drift over desert surfaces, soil blowing over fields, and snow drift over smooth surfaces such as those in the Arctic or Canadian Prairies. Process At low fluid velocities, loose material rolls downstream, staying in contact with the surface. This is called ''creep'' or ''reptation''. Here the forces exerted by the fluid on the particle are only enough to roll the particle around the point of contact with the surface. Once the wind speed reaches a certain critical value, termed the ''impact'' or ''fluid threshold'', the drag and lift forces exerted by the fluid are sufficient to lift some particles from the surface. These particles are accelerated by the fluid, and pulled downward by gravity, causing them t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deposition (geology)
Deposition is the geological process in which sediments, soil and rock (geology), rocks are added to a landform or landmass. Wind, ice, water, and gravity Transportation (sediment), transport previously Weathering, weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment. This occurs when the forces responsible for sediment transportation are no longer sufficient to overcome the forces of gravity and friction, creating a resistance to motion; this is known as the null-point hypothesis. Deposition can also refer to the buildup of sediment from Organic matter, organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which induced chemical processes (diagenesis) to deposit further calcium carbonate. Similarly, the formation of coal begins with the deposition of organic material, mainly from plants ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bernoulli Effect
Bernoulli's principle is a key concept in fluid dynamics that relates pressure, speed and height. For example, for a fluid flowing horizontally Bernoulli's principle states that an increase in the speed occurs simultaneously with a decrease in pressure The principle is named after the Swiss mathematician and physicist Daniel Bernoulli, who published it in his book ''Hydrodynamica'' in 1738. Although Bernoulli deduced that pressure decreases when the flow speed increases, it was Leonhard Euler in 1752 who derived Bernoulli's equation in its usual form. Bernoulli's principle can be derived from the principle of conservation of energy. This states that, in a steady flow, the sum of all forms of energy in a fluid is the same at all points that are free of viscous forces. This requires that the sum of kinetic energy, potential energy and internal energy remains constant. Thus an increase in the speed of the fluid—implying an increase in its kinetic energy—occurs with a simultan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment Transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting. Sediment transport due to fluid motion occurs in rivers, oceans, lakes, seas, and other bodies of water due to current (fluid), currents and tides. Transport is also caused by glaciers as they flow, and on terrestrial surfaces under the influence of wind. Sediment transport due only to gravity can occur on sloping surfaces in general, including hillslopes, escarpment, scarps, cliffs, and the continental shelf—continental slope boundary. Sediment transport is important in the fields of sedimentary geology, geomorphology, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Canadian Encyclopedia
''The Canadian Encyclopedia'' (TCE; ) is the national encyclopedia of Canada, published online by the Toronto-based historical organization Historica Canada, with financial support by the federal Department of Canadian Heritage and Society of Composers, Authors and Music Publishers of Canada. Compiled by more than 5,000 scholars and specialists, the publication is a non-partisan, non-political initiative by a not-for-profit organization without political or governmental ties. First published in 1985, the consistently updated version has been available for free online in both Canadian English, English and Canadian French, French since 2001. The physical copy and website includes "articles on Canadian biographies and places, history, the Arts, as well as First Nations, science and Canadian innovation." , over 700,000 volumes of the print version of ''TCE'' have been sold and over 6 million people visit ''TCE'''s website yearly. The encyclopedia website consists of more than 25,000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
