Sediment transport
Sediment transport is the movement of solid particles due to a combination of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are mud, or clay. Sediment transport due to fluid motion occurs in rivers, lakes and other bodies of water due to currents and tides. Transport is caused by glaciers as they flow, on terrestrial surfaces under the influence of wind. Sediment transport due only to gravity can occur on sloping surfaces in general, including hillslopes, scarps and the continental shelf—continental slope boundary. Sediment transport is important in the fields of sedimentary geology, civil engineering and environmental engineering. Knowledge of sediment transport is most used to determine whether erosion or deposition will occur, the magnitude of this erosion or deposition, the time and distance over which it will occur. Aeolian or eolian is the term for sediment transport by wind.
This process results in the formation of ripples and sand dunes. The size of the transported sediment is fine sand and smaller, because air is a fluid with low density and viscosity, can therefore not exert much shear on its bed. Bedforms are generated by aeolian sediment transport in the terrestrial near-surface environment. Ripples and dunes form as a natural self-organizing response to sediment transport. Aeolian sediment transport is common on beaches and in the arid regions of the world, because it is in these environments that vegetation does not prevent the presence and motion of fields of sand. Wind-blown fine-grained dust is capable of entering the upper atmosphere and moving across the globe. Dust from the Sahara deposits on the Canary Islands and islands in the Caribbean, dust from the Gobi desert has deposited on the western United States; this sediment is important to the soil ecology of several islands. Deposits of fine-grained wind-blown glacial sediment are called loess. In geology, physical geography, sediment transport, fluvial processes relate to flowing water in natural systems.
This encompasses rivers, periglacial flows, flash floods and glacial lake outburst floods. Sediment moved by water can be larger than sediment moved by air because water has both a higher density and viscosity. In typical rivers the largest carried sediment is of sand and gravel size, but larger floods can carry cobbles and boulders. Fluvial sediment transport can result in the formation of ripples and dunes, in fractal-shaped patterns of erosion, in complex patterns of natural river systems, in the development of floodplains. Coastal sediment transport takes place in near-shore environments due to the motions of waves and currents. At the mouths of rivers, coastal sediment and fluvial sediment transport processes mesh to create river deltas. Coastal sediment transport results in the formation of characteristic coastal landforms such as beaches, barrier islands, capes; as glaciers move over their beds, they move material of all sizes. Glaciers can carry the largest sediment, areas of glacial deposition contain a large number of glacial erratics, many of which are several metres in diameter.
Glaciers pulverize rock into "glacial flour", so fine that it is carried away by winds to create loess deposits thousands of kilometres afield. Sediment entrained in glaciers moves along the glacial flowlines, causing it to appear at the surface in the ablation zone. In hillslope sediment transport, a variety of processes move regolith downslope; these include: Soil creep Tree throw Movement of soil by burrowing animals Slumping and landsliding of the hillslopeThese processes combine to give the hillslope a profile that looks like a solution to the diffusion equation, where the diffusivity is a parameter that relates to the ease of sediment transport on the particular hillslope. For this reason, the tops of hills have a parabolic concave-up profile, which grades into a convex-up profile around valleys; as hillslopes steepen, they become more prone to episodic landslides and other mass wasting events. Therefore, hillslope processes are better described by a nonlinear diffusion equation in which classic diffusion dominates for shallow slopes and erosion rates go to infinity as the hillslope reaches a critical angle of repose.
Large masses of material are moved in debris flows, hyperconcentrated mixtures of mud, clasts that range up to boulder-size, water. Debris washes; because they transport sediment as a granular mixture, their transport mechanisms and capacities scale differently from those of fluvial systems. Sediment transport is applied to solve many environmental and geological problems. Measuring or quantifying sediment transport or erosion is therefore important for coastal engineering. Several sediment erosion devices have been designed in order to quantitfy sediment erosion. One such device referred to as the BEAST has been calibrated in order to quantify rates of sediment erosion. Movement of sediment is important in providing habitat for fish and other organisms in rivers. Therefore, managers of regulated rivers, which are sediment-starved due to dams, are advised to stage short floods to refresh the bed material and rebuild bars
Glacial motion
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 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, internal deformation. In the case of basal sliding, the entire glacier slides over its bed; this type of motion is enhanced if the bed is soft sediment, if the glacier bed is thawed and if meltwater is prevalent. 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; some glaciers experience glacial quakes—glaciers "as large as Manhattan and as tall as the Empire State Building, can move 10 meters in less than a minute, a jolt, sufficient to generate moderate seismic waves."
There has been an increasing pattern of these ice quakes - "Quakes ranged from six to 15 per year from 1993 to 2002 jumped to 20 in 2003, 23 in 2004, 32 in the first 10 months of 2005." A glacier, frozen up to its bed does not experience basal sliding. Internal deformation occurs; this takes place most near the glacier bed, where pressures are highest. There are glaciers that move via sliding, glacial quakes, others that move entirely through deformation. If a glacier's 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 striking 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.
Studying glacial motion and the landforms that result requires tools from many different disciplines: physical geography and geology are among the areas sometime grouped together and called earth science. 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. As the glaciers were expanded, due to their accumulating weight of snow and ice, they crushed and redistributed surface rocks, creating erosional landforms such as striations and hanging valleys; when the glaciers retreated leaving behind their freight of crushed rock and sand, depositional landforms were created, such as moraines, eskers and kames. The stone walls found in New England contain many glacial erratics, rocks that were dragged by a glacier many miles from their bedrock origin. 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 become clearer as glacial flour diminishes. Lakes and ponds can be caused by glacial movement. Kettle lakes form. Moraine-dammed lakes occur. Cryoseism Glacial earthquake Glacial lake outburst flood How glaciers form and flow Trends in glacier mass balance Animation of glacial advance Advance and retreat of Columbia Glacier in Prince William Sound Physical geography of glacial landforms Links to more glacier resources online North Cascade Glacier Climate Project Research
Silt
Silt is granular material of a size between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil or as sediment mixed in suspension with water and soil in a body of water such as a river, it may exist as soil deposited at the bottom of a water body, like mudflows from landslides. Silt has a moderate specific area with a non-sticky, plastic feel. Silt has a floury feel when dry, a slippery feel when wet. Silt can be visually observed with a hand lens, it can be felt by the tongue as granular when placed on the front teeth. Silt is created by a variety of physical processes capable of splitting the sand-sized quartz crystals of primary rocks by exploiting deficiencies in their lattice; these involve chemical weathering of rock and regolith, a number of physical weathering processes such as frost shattering and haloclasty. The main process is abrasion through transport, including fluvial comminution, aeolian attrition and glacial grinding, it is in semi-arid environments.
Silt is sometimes known as "rock flour" or "stone dust" when produced by glacial action. Mineralogically, silt is composed of quartz and feldspar. Sedimentary rock composed of silt is known as siltstone. Liquefaction created by a strong earthquake is silt suspended in water, hydrodynamically forced up from below ground level. In the Udden–Wentworth scale, silt particles range between 0.0039 and 0.0625 mm, larger than clay but smaller than sand particles. ISO 14688 grades silts between 0.063 mm. In actuality, silt is chemically distinct from clay, unlike clay, grains of silt are the same size in all dimensions. Clays are formed from thin plate-shaped particles held together by electrostatic forces, so present a cohesion. Pure silts are not cohesive. According to the U. S. Department of Agriculture Soil Texture Classification system, the sand–silt distinction is made at the 0.05 mm particle size. The USDA system has been adopted by the Agriculture Organization. In the Unified Soil Classification System and the AASHTO Soil Classification system, the sand–silt distinction is made at the 0.075 mm particle size.
Silts and clays are distinguished mechanically by their plasticity. Silt is transported in water or other liquid and is fine enough to be carried long distances by air in the form of dust. Thick deposits of silty material resulting from deposition by aeolian processes are called loess. Silt and clay contribute to turbidity in water. Silt is transported by water currents in the ocean; when silt appears as a pollutant in water the phenomenon is known as siltation. Silt, deposited by annual floods along the Nile River, created the rich, fertile soil that sustained the Ancient Egyptian civilization. Silt deposited by the Mississippi River throughout the 20th century has decreased due to a system of levees, contributing to the disappearance of protective wetlands and barrier islands in the delta region surrounding New Orleans. In southeast Bangladesh, in the Noakhali district, cross dams were built in the 1960s whereby silt started forming new land called "chars"; the district of Noakhali has gained more than 73 square kilometres of land in the past 50 years.
With Dutch funding, the Bangladeshi government began to help develop older chars in the late 1970s, the effort has since become a multi-agency operation building roads, embankments, cyclone shelters and ponds, as well as distributing land to settlers. By fall 2010, the program will have allotted some 100 square kilometres to 21,000 families. A main source of silt in urban rivers is disturbance of soil by construction activity. A main source in rural rivers is erosion from plowing of farm fields, clearcutting or slash and burn treatment of forests; the fertile black silt of the Nile river's banks is a symbol of rebirth, associated with the Egyptian god Anubis. Erosion control Nonpoint source pollution Sediment control Silt fence Siltation
Meltwater
Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during volcanic eruptions, in a similar way in which the more dangerous lahars form; when meltwater pools on the surface rather than flowing, it forms melt ponds. As the weather gets colder meltwater will re-freeze. Meltwater can melt under the ice's surface; these pools of water, known as subglacial lakes can form due to geothermal friction. Meltwater provides drinking water for a large proportion of the world's population, as well as providing water for irrigation and hydroelectric plants; some cities around the world have large lakes. Cities that source water from meltwater include Melbourne, Los Angeles, Las Vegas amongst others. Glacial meltwater comes by pressure and geothermal heat. There will be rivers flowing through glaciers into lakes; these brilliantly blue lakes get their color from "rock flour", sediment, transported through the rivers to the lakes.
This sediment comes from rocks grinding together underneath the glacier. The fine powder is suspended in the water and absorbs and scatters varying colors of sunlight, giving a milky turquoise appearance. Meltwater acts as a lubricant in the basal sliding of glaciers. GPS measurements of ice flow have revealed that glacial movement is greatest in summer when the meltwater levels are highest. Meltwater can be an indication of abrupt climate change. An instance of a large meltwater body is the case of the region of a tributary of Bindschadler Ice Stream, West Antarctica where rapid vertical motion of the ice sheet surface has suggested shifting of a subglacial water body, it can destabilize glacial lakes leading to sudden floods, destabilize snowpack causing avalanches. Dammed glacial meltwater from a moraine-dammed lake, released can result in the floods, such as those that created the granite chasms in Purgatory Chasm State Reservation. In a report published in June 2007, the United Nations Environment Programme estimated that global warming could lead to 40% of the world population being affected by the loss of glaciers and the associated meltwater in Asia.
The predicted trend of glacial melt signifies seasonal climate extremes in these regions of Asia. Meltwater pulse 1A was a prominent feature of the last deglaciation and took place 14.7-14.2 thousand years ago. Extreme Ice Survey Groundwater Kryal Moulin Snowmelt Surface water June 4, 2007, BBC: UN warning over global ice loss United Nations Environment Program: Global Outlook for Ice and Snow
United States Department of Agriculture
The United States Department of Agriculture known as the Agriculture Department, is the U. S. federal executive department responsible for developing and executing federal laws related to farming and food. It aims to meet the needs of farmers and ranchers, promote agricultural trade and production, work to assure food safety, protect natural resources, foster rural communities and end hunger in the United States and internationally. 80% of the USDA's $141 billion budget goes to the Food and Nutrition Service program. The largest component of the FNS budget is the Supplemental Nutrition Assistance Program, the cornerstone of USDA's nutrition assistance; the current Secretary of Agriculture is Sonny Perdue. Many of the programs concerned with the distribution of food and nutrition to people of America and providing nourishment as well as nutrition education to those in need are run and operated under the USDA Food and Nutrition Service. Activities in this program include the Supplemental Nutrition Assistance Program, which provides healthy food to over 40 million low-income and homeless people each month.
USDA is a member of the United States Interagency Council on Homelessness, where it is committed to working with other agencies to ensure these mainstream benefits are accessed by those experiencing homelessness. The USDA is concerned with assisting farmers and food producers with the sale of crops and food on both the domestic and world markets, it plays a role in overseas aid programs by providing surplus foods to developing countries. This aid can go through USAID, foreign governments, international bodies such as World Food Program, or approved nonprofits; the Agricultural Act of 1949, section 416 and Agricultural Trade Development and Assistance Act of 1954 known as Food for Peace, provides the legal basis of such actions. The USDA is a partner of the World Cocoa Foundation. Early in its history, the economy of the United States was agrarian. Officials in the federal government had long sought new and improved varieties of seeds and animals for import into the United States. In 1837 Henry Leavitt Ellsworth, a Yale-educated attorney interested in improving agriculture, became Commissioner of Patents, a position within the Department of State.
He began collecting and distributing new varieties of seeds and plants through members of the Congress and agricultural societies. In 1839, Congress established the Agricultural Division within the Patent Office and allotted $1,000 for "the collection of agricultural statistics and other agricultural purposes." Ellsworth's interest in aiding agriculture was evident in his annual reports that called for a public depository to preserve and distribute the new seeds and plants, a clerk to collect agricultural statistics, statewide reports about crops in different regions, the application of chemistry to agriculture. Ellsworth was called the "Father of the Department of Agriculture."In 1849, the Patent Office was transferred to the newly created Department of the Interior. In the ensuing years, agitation for a separate bureau of agriculture within the department or a separate department devoted to agriculture kept recurring. On May 15, 1862, Abraham Lincoln established the independent Department of Agriculture to be headed by a commissioner without Cabinet status, the agriculturalist Isaac Newton was appointed to be the first such commissioner.
Lincoln called it the "people's department." In 1868, the Department moved into the new Department of Agriculture Building in Washington, D. C. designed by famed DC architect Adolf Cluss. Located on Reservation No.2 on the National Mall between 12th Street and 14th SW, the Department had offices for its staff and the entire width of the Mall up to B Street NW to plant and experiment with plants. In the 1880s, varied advocacy groups were lobbying for Cabinet representation. Business interests sought a Department of Commerce and Industry, farmers tried to raise the Department of Agriculture to Cabinet rank. In 1887, the House of Representatives and Senate passed bills giving Cabinet status to the Department of Agriculture and Labor, but the bill was defeated in conference committee after farm interests objected to the addition of labor. On February 9, 1889, President Grover Cleveland signed a bill into law elevating the Department of Agriculture to Cabinet level. In 1887, the Hatch Act provided for the federal funding of agricultural experiment stations in each state.
The Smith-Lever Act of 1914 funded cooperative extension services in each state to teach agriculture, home economics, other subjects to the public. With these and similar provisions, the USDA reached out to every county of every state. During the Great Depression, farming remained a common way of life for millions of Americans; the Department of Agriculture's Bureau of Home Economics, established in 1923, published shopping advice and recipes to stretch family budgets and make food go farther. USDA helped ensure that food continued to be produced and distributed to those who needed it, assisted with loans for small landowners, contributed to the education of the rural youth, it was revealed on August 27th, 2018 that the U. S. Department of Agriculture would be providing U. S. farmers with a farm aid package, which will total $4.7 billion in direct payments to American farmers. This package is meant to offset the losses farmers are expected to incur from retaliatory tariffs placed on American exports during the Trump tariffs.
The Department of Agriculture was authorized a budget for Fiscal Year 2015 of $139.7 billion. The budget authorization is broken down as follows: Agricultural Stabilization and Conservation Service Animal Damage Control (
Peyto Lake
Peyto Lake is a glacier-fed lake in Banff National Park in the Canadian Rockies. The lake itself is accessed from the Icefields Parkway, it was named for an early trail guide and trapper in the Banff area. The lake is formed in a valley of the Waputik Range, between Caldron Peak, Peyto Peak and Mount Jimmy Simpson, at an elevation of 1,860 m. During the summer, significant amounts of glacial rock flour flow into the lake, these suspended rock particles give the lake a bright, turquoise colour; because of its bright colour, photos of the lake appear in illustrated books, the area around the lake is a popular sightseeing spot for tourists. The lake is best seen from the highest point on the Icefields Parkway; the lake is fed by Peyto Creek, which drains water from Peyto Glacier. Peyto Lake is the origin of the Mistaya River. Media related to Peyto Lake at Wikimedia Commons Peyto Lake travel guide from Wikivoyage Parks Canada - Banff National Park
Emerald Lake (British Columbia)
Emerald Lake is located in Yoho National Park, British Columbia, Canada. It is the largest of Yoho's 61 lakes and ponds, as well as one of the park's premier tourist attractions. Emerald Lake Lodge, a high-end lodge perched on the edge of the lake, provides local accommodation. A 5.2 km hiking trail circuits the lake, the first half of, accessible to wheelchairs and strollers. During the summer months, canoe rentals are available; the lake is enclosed by mountains of the President Range, as well as Mount Burgess and Wapta Mountain. This basin traps storms; this influx of moisture works with the lake's low elevation to produce a unique selection of flora. Trees found here are more typical of B. C.'s wet interior forests, such as western red cedar, western yew, western hemlock and western white pine. The alluvial fan on the northeast shore produces wildflowers in abundance during late June and early July. Due to its high altitude, the lake is frozen from November until June; the vivid turquoise color of the water, caused by powdered limestone, is most spectacular in July as the snow melts from the surrounding mountains.
The first non-indigenous person to set sight on Emerald Lake was Canadian guide Tom Wilson, who stumbled upon it by accident in 1882. A string of his horses had gotten away, it was while tracking them that he first entered the valley; the lake had an impression on the most seasoned of explorers: "For a few moments I sat my horse and enjoyed the rare, peaceful beauty of the scene." It was Wilson who gave the lake its name because of its remarkable colour, caused by fine particles of glacial sediment referred to as rock flour, suspended in the water. However, this was not the first time Wilson had dubbed a lake'Emerald'. Earlier that same year he had discovered another lake which he had given the same moniker, the name appeared on the official map; this first lake however, was shortly renamed Lake Louise. List of lakes in Yoho National Park Media related to Emerald Lake at Wikimedia Commons
