1.
Sorting (sediment)
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Sorting describes the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks. This should not be confused with crystallite size, which refers to the size of a crystal in a solid. Crystallite is the block of a grain. Very poorly sorted indicates that the sediment sizes are mixed, whereas well sorted indicates that the sediment sizes are similar, in the field, sedimentologists use graphical charts to accurately describe the sorting of a sediment using one of these words. The degree of sorting may also indicate the energy, rate, and/or duration of deposition, sorting of sediments can also be affected by reworking of the material after deposition, for instance, by winnowing. Well sorted rocks are generally porous, while poorly sorted rocks have low porosity, grain size Graded bedding Rounding Porosity Soil texture Sediment transport
2.
Glacier
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A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs and they also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia also have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue. The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
3.
Erosion
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In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, then transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are also possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, however, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
4.
Glacial motion
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Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes, most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast or slow, but is typically around 1 metre/day, glacier motion occurs from four processes, all driven by gravity, basal sliding, glacial quakes generating fractional movements of large sections of ice, bed deformation, and internal deformation. In the case of basal sliding, the glacier slides over its bed. This type of motion is enhanced if the bed is soft sediment, if the bed is thawed. Bed deformation is thus limited to areas of sliding. Seasonal melt ponding and penetrating under glaciers shows seasonal acceleration and deceleration of ice flows affecting whole icesheets. There has been a pattern of these ice quakes - Quakes ranged from six to 15 per year from 1993 to 2002, then jumped to 20 in 2003,23 in 2004. A glacier that is frozen up to its bed does not experience basal sliding, internal deformation occurs when the weight of the ice causes the deformation of ice crystals. This takes place most readily near the bed, where pressures are highest. There are glaciers that primarily move via sliding, glacial quakes, if a glaciers terminus moves forward faster than it melts, the net result is advance. Glacier retreat occurs when more material ablates from the terminus than is replenished by flow into that region, glaciologists consider that trends in mass balance for glaciers are more fundamental than the advance or retreat of the termini of individual glaciers. In the years since 1960, there has been a decline in the overall volume of glaciers worldwide. This decline is correlated with global warming, as a glacier thins, due to the loss of mass it will slow down and crevassing will decrease. During the Pleistocene, huge sheets of ice called continental glaciers advanced over much of the earth, the movement of these continental glaciers created many now-familiar glacial landforms. Later, when the glaciers retreated leaving behind their freight of crushed rock and sand, depositional landforms were created, such as moraines, eskers, drumlins, and kames. The stone walls found in New England contain many glacial erratics, at some point, if an Alpine glacier becomes too thin it will stop moving. This will result in the end of any basal erosion, the stream issuing from the glacier will then become clearer as glacial flour diminishes
5.
Deposition (geology)
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Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass. Deposition can also refer to the buildup of sediment from 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 has induced chemical processes to deposit further calcium carbonate. Similarly, the formation of coal begins with deposition of material, mainly from plants. The null-point hypothesis explains how sediment is deposited throughout a shore profile according to its grain size and this is due to the influence of hydraulic energy, resulting in a seaward-fining of sediment particle size, or where fluid forcing equals gravity for each grain size. The concept can also be explained as sediment of a particular size may move across the profile to a position where it is in equilibrium with the wave, figure 1 illustrates this relationship between sediment grain size and the depth of the marine environment. The relatively strong onshore stroke of the forms a eddy or vortex on the lee side of the ripple, provided the onshore flow persists. Where there is symmetry in ripple shape the vortex is neutralised and this creates a cloudy water column which travels under tidal influence as the wave orbital motion is in equilibrium. R is the radius of the object, ρ is the mass density of the fluid, g is the gravitational acceleration, Cd is the drag coefficient. When the fluid becomes more viscous due to grain sizes or larger settling velocities, prediction is less straight forward. Cohesion of sediment occurs with the grain sizes associated with silts and clays. Akaroa Harbour is located on Banks Peninsula, Canterbury, New Zealand and this research shows conclusive evidence for the null point theory existing on tidal flats with differing hydrodynamic energy levels and also on flats that are both erosional and accretional. Kirby R. Cheniers can be found at any level on the foreshore and this is because sediment grain size analysis throughout a profile allows inference into the erosion or accretion rates possible if shore dynamics are modified. Planners and managers should also be aware that the environment is dynamic. Cementation Cross-bedding Drift Flocculation Longshore drift Overbank Sedimentary rock Sedimentary structures Settling Shields parameter Stokes law Superficial deposits
6.
Terminal moraine
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A terminal moraine, also called end moraine, is a type of moraine that forms at the snout of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, because the glacier acts very much like a conveyor belt, the longer it stays in one place, the greater the amount of material that will be deposited. The moraine is left as the point of the terminal extent of the ice. Terminal moraines are one of the most prominent types of moraines in the Arctic, one famous terminal moraine is the Giants Wall in Norway which, according to legend, was built by giants to keep intruders out of their realm. In North America, the Outer Lands is a given to the terminal moraine archipelago of the northeastern region of the United States. Other prominent examples of terminal moraines are the Tinley Moraine and the Valparaiso Moraine and these moraines are most clearly seen southwest of Chicago. In Europe, virtually all the terrain in the central Netherlands is made up of a terminal moraine. In New Zealand the Franz Josef Glacier on the West Coast has created the terminal called the Waiho Loop. Glacial landform Postglacial rebound Push moraine Outwash plain Trafalgar Moraine Oak Ridges Moraine List of glacial moraines
7.
Moraine
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A moraine is any glacially formed accumulation of unconsolidated glacial debris that occurs in both currently and formerly glaciated regions on Earth, through geomorphological processes. Moraines are formed from debris previously carried along by a glacier, lateral moraines are formed at the side of the ice flow and terminal moraines at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines, till-covered areas with irregular topography, moraines may be composed of debris ranging in size from silt-sized glacial flour to large boulders. The debris is typically sub-angular to rounded in shape, moraines may be on the glacier’s surface or deposited as piles or sheets of debris where the glacier has melted. Moraines may form through a number of processes, depending on the characteristics of sediment, the dynamics on the ice, moraine forming processes may be loosely divided into passive and active. Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking and these moraines are composed of supraglacial sediments from the ice surface. Active processes form or rework moraine sediment directly by the movement of ice and these form push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment. Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin and these fan deposits may coalesce to form a long moraine bank marking the ice margin. Several processes may combine to form and rework a single moraine, moraines can be classified either by origin, location with respect to a glacier or former glacier, or by shape. Some moraine types are only from ancient glaciers, while medial moraines of valley glaciers are poorly preserved. Lateral moraines are parallel ridges of debris deposited along the sides of a glacier, the unconsolidated debris can be deposited on top of the glacier by frost shattering of the valley walls and/or from tributary streams flowing into the valley. The till is carried along the glacial margin until the glacier melts, lateral moraines stand high because they protect the ice under them from the elements, causing it to melt or sublime less than the uncovered parts of the glacier. Multiple lateral moraines may develop as the glacier advances and retreats, ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains. They are accumulated at the base of the ice as lodgment till, in alpine glaciers, ground moraines are often found between the two lateral moraines. Ground moraines may be modified into drumlins by the overriding ice, Rogen moraines or ribbed moraines are a type of basal moraines that form a series of ribs perpendicular to the ice flow in an ice sheet. The depressions between the ribs are sometimes filled with water, making the Rogen moraines look like tigerstripes on aerial photographs, Rogen moraines are named after Lake Rogen in Härjedalen, Sweden, the landform’s type locality. End moraines, or terminal moraines, are ridges of unconsolidated debris deposited at the snout or end of the glacier and they usually reflect the shape of the glaciers terminus. Glaciers act much like a belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines
8.
Fluvial
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Fluvial is a term used in geography and geology to refer to the processes associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, fluvial processes include the motion of sediment and erosion or deposition on the river bed. Erosion by moving water can happen in two ways, firstly, the movement of water across the bed exerts a shear stress directly onto the bed. However, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed, at the same time the fragments themselves are ground down, becoming smaller and more rounded. Sediment in rivers is transported as either bedload or suspended load, there is also a component carried as dissolved material. For each grain size there is a velocity at which the grains start to move. However the grains will continue to be transported even if the velocity falls below the entrainment velocity due to the friction between the grains and the river bed. Eventually the velocity will fall low enough for the grains to be deposited and this is shown by the Hjulstrøm curve. A river is continually picking up and dropping solid particles of rock, where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up, areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium. Even small streams make alluvial deposits, but it is in the plains and deltas of large rivers that large. The amount of matter carried by a river is enormous. The names of rivers derive from the color that the transported matter gives the water. For example, the Huang He in China is literally translated Yellow River, and it has been estimated that the Mississippi River annually carries 406 million tons of sediment to the sea, the Yellow River 796 million tons, and the Po River in Italy 67 million tons. Lacustrine - of or relating to a lake maritime - of or relating the sea oceanic - of or relating to an ocean palustrine - of or relating to a marsh
9.
Sediment
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For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
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