Water Erosion Rates Essay Example for Free

Water Erosion rank EssayA infixed arch produced by the corroding of differenti eachy weathered rock in Jebel Kharaz, Jordan Erosion is the figure out by which soil and rock atomic number 18 removed from the Earths resurrect by natural processes such(prenominal) as envelop or wet lam, and then transported and deposited in another(prenominal) locations. While wearing by is a natural process, human activities make pissing dramatically increased (by 10-40 times) the rate at which erosion is occurring globally. undue erosion ca wasting diseases problems such as desertification, decreases in agricultural productivity due to land degradation, sedimentation of waterways, and bionomic collapse due to loss of the nutrient rich upper soil layers. Water and crest erosion are now the two primary causes of land degradation combined, they are responsible for 84% of adulterate acreage, making excessive erosion one of the most significant global env squeezemental problems we fac e today.12 industrial agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regards to their effect on stimulating erosion.3 However, there are many available alternative land use practices that can curtail or limit erosionsuch as terrace-building, no-till agriculture, and revegetation of denuded soils.Frost weatheringFrom Wikipedia, the resign encyclopedia(Redirected from Frost action)Aly by mechanical frost weathering or thermal stressFrost weathering is a collective call for some(prenominal) mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedging and cryofracturing. The process may act on a wide range of spatial and temporal scales, from minutes to years and from dislodging mineral grains to fracturing boulders. Frost weathering is mainly bringn by the freq uency and ecstasy of freeze-thaw cycles and the properties of the materials subject to weathering. It is most sound out in blue altitude and latitude areas and is especially associated with alpine, periglacial, subpolar maritime and polar climates but occurs wherever freeze-thaw cycles are present. * When water freezes to ice, its volume increases by nine percent. Under specific circumstances, this magnification is able to displace or fracture rock. At a temperature of -22 C, ice growth is known to be able to generate hauls of up to 207MPa, much than than enough to fracture any rock.12 For frost weathering to occur by volumetric expansion, the rock must(prenominal) suck in almost no air that can be compressed to compensate for the expansion of ice, which bureau it has to be water- double-dyed(a) and frozen quickly from all sides so that the water does not migrate away and the pressure is exerted on the rock.1 These conditions are considered unusual,1 restricting it to a pr ocess of importance within a few centimeters of a rocks surface and on outstandingr existing water-filled joints in a process called ice wedging. Not all volumetric expansion is caused by the pressure of the freezing water it can be caused by stresses in water that remains unfrozen.When ice growth induces stresses in the pore water that breaks the rock, the result is called hydrofracture. Hydrofracturing is favoured by large interconnected pores or large hydraulic gradients in the rock. If there are small pores, a genuinely quick freezing of water in parts of the rock may expel water, and if the water is expelled smart than it can migrate, pressure may rise, fracturing the rock. Since research in physical weathering begun around 1900, volumetric expansion was, until the 1980s, held to be the predominant process behind frost weathering.3 This view was challenged in 1985 and 1986 publications by Walder and Hallet.13 Nowadays researchers such as Matsuoka and Murton consider the cond itions necessary for Biological weatheringA number of embeds and animals may create chemical substance weathering through produce of stingingic compounds, i.e. moss on roofs is classed as weathering. Mineral weathering can too be initiated and/or accelerated by soil microorganisms. Lichens on rocks are thought to increase chemical weathering range. For example, an experimental study on hornblende granite in New Jersey, USA, demonstrated a 3x 4x increase in weathering rate under lichen covered surfaces compared to recently assailable bare rock surfaces.7The most common forms of biological weathering are the release of chelating compounds (i.e. organic acids, siderophores) and of acidifying molecules (i.e. protons, organic acids) by plants so as to break down aluminium and iron containing compounds in the soils beneath them. Decaying remains of unfounded plants in soil may form organic acids which, when dissolved in water, cause chemical weathering.citation needed primitive r elease of chelating compounds can easily affect surrounding rocks and soils, and may lead to podsolisation of soils. The symbiotic mycorrhizal fungi associated with tree root systems can release inorganic nutrients from minerals such as apatite or biotite and transfer these nutrients to the trees, thus bestow to tree nutrition.8It was also recently evidenced that bacterial communities can impact mineral stability starring(p) to the release of inorganic nutrients.9 To date a large range of bacterial strains or communities from diverse genera have been reported to be able to colonize mineral surfaces and/or to weather minerals, and for some of them a plant growth promoting effect was demonstrated.10 The demonstrated or hypothesised mechanisms used by bacteria to weather minerals include several oxidoreduction and dissolution replys as well as the production of weathering agents, such as protons, organic acids and chelating molecules. oxidizationWithin the weathering environment ch emical oxidisation of a variety of metals occurs. The most commonly observed is the oxidation of Fe2+ (iron) and combination with oxygen and water to form Fe3+ hydroxides and oxides such as goethite, limonite, and hematite. This gives the affected rocks a reddish-brown colour on the surface which crumbles easily and weakens the rock. This process is better known as rust fungus, though it is distinct from the rusting of metallic iron. Many other metallic ores and minerals oxidize and hydrate to produce colored deposits, such as chalcopyrites or CuFeS2 oxidizing to copper hydroxide and iron oxides.Dissolution and carbonationA pyrite cube has dissolved away from host rock, leaving gold behind Rainfall is acidic because atmospheric carbon dioxide dissolves in the pelting producing weak carbonic acid. In unpolluted environments, the rainfall pH is around 5.6. Acid rain occurs when gases such as sulfur dioxide and nitrogen oxides are present in the atmosphere. These oxides react in the rain water to produce stronger acids and can lower the pH to 4.5 or even 3.0. Sulfur dioxide, SO2, comes from volcanic eruptions or from dodo fuels, can become sulfuric acid within rainwater, which can cause solution weathering to the rocks on which it falls. well-nigh minerals, due to their natural solubility (e.g. evaporites), oxidation potential (iron-rich minerals, such as pyrite), or instability congress to surficial conditions (see Goldich dissolution series) go forth weather through dissolution naturally, even without acidic water. Exfoliation is a type of erosion that occurs when a rock is rapidly heated up by the sun. This results in the expansion of the rock. When the temperature decreases again, the rock contracts, causing pieces of the rock to break off. Exfoliation occurs mainly in deserts due to the extravagantly temperatures during the day and cold temperatures at night.24HydrationMineral hydration is a form of chemical weathering that involves the rigid attachme nt of H+ and OH- ions to the atoms and molecules of a mineral. When rock minerals take up water, the increased volume creates physical stresses within the rock. For example iron oxides are converted to iron hydroxides and the hydration of anhydrite forms gypsum.A freshly broken rock shows differential chemical weathering (probably in general oxidation) progressing inward. This piece of sandstone was found in glacial drift near Angelica, New York Hydrolysis on silicates and carbonatesHydrolysis is a chemical weathering process affecting silicate and carbonate minerals. In such reactions, pure water ionizes slightly and reacts with silicate minerals. An example reaction This reaction theoretically results in complete dissolution of the original mineral, if enough water is available to drive the reaction. In reality, pure water rarely acts as a H+ donor. Carbon dioxide, though, dissolves readily in water forming a weak acid and H+ donor. This hydrolysis reaction is much more common. C arbonic acid is consumed by silicate weathering, resulting in more alkaline solutions because of the bicarbonate. This is an important reaction in controlling the amount of carbon dioxide in the atmosphere and can affect climate. Aluminosilicates when subjected to the hydrolysis reaction produce a secondary mineral kind of than simply releasing cations.RainfallThere are three primary types of erosion that occur as a direct result of rainfallsheet erosion, rill erosion, and gully erosion. Sheet erosion is generally seen as the first and least severe stage in the soil erosion process, which is followed by rill erosion, and lastly gully erosion (the most severe of the three).45 The impact of a falling raindrop creates a small crater in the soil, ejecting soil particles. The distance these soil particles travel (on level ground) can be as much as 2 feet vertically, and 5 feet horizontally. Once the rate of rain fall is faster than the rate of infiltration into the soil, surface runoff occurs and carries the loosened soil particles down slope.6Rill 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 on the order of a few centimeters or less and slopes may be sooner steep. This means that rills exhibit very different hydraulic physics than water flowing through the deeper, wider conduct of streams and rivers. Gully erosion occurs when runoff water accumulates, and then rapidly flows in narrow channels during or now after heavy rains or melting snow, removing soil to a considerable depth.Factors affecting erosion ratesClimatic factors include the amount and intensity of precipitation, the average temperature, as well as the typical temperature range, seasonality, wind speed, and storm frequency. In general, given si milar vegetation and ecosystems, areas with high-intensity precipitation, more frequent rainfall, more wind, or more storms are expected to have more erosion.citation needed Rainfall intensity is the primary determinant of erosivity, with higher(prenominal) intensity rainfall generally resulting in more erosion. The size and velocity of rain drops is also an important factor. bigger and higher-velocity rain drops have greater kinetic energy, and thus their impact will displace soil particles by larger distances than smaller, slower-moving rain drops.25Erosional gully in unconsolidated Dead Sea (Israel) sediments along the southwestern shore. This gully was excavated by floods from the Judean Mountains in less than a year. The composition, moisture, and compaction of soil are all major factors in determining the erosivity of rainfall. Sediments containing more clay tend to be more resistant to erosion than those with sand or silt, because the clay helps control soil particles togeth er.26 Soil containing high levels of organic materials are often more resistant to erosion, because the organic materials clabber soil colloids and create a stronger, more stable soil structure.27The amount of water present in the soil before the precipitation also plays an important role, because it sets limits on the amount of water that can be absorbed by the soil (and hence prevented from flowing on the surface as erosive runoff). Wet, saturated soils will not be able to absorb as much rain water, leading to higher levels of surface runoff and thus higher erosivity for a given volume of rainfall.2728 Soil compaction also affects the permeability of the soil to water, and hence the amount of water that flows away as runoff. More compacted soils will have a larger amount of surface runoff than less compacted soils.27Vegetative coverVegetation acts as an interface between the atmosphere and the soil. It increases the permeability of the soil to rainwater, thus decreasing runoff. I t shelters the soil from winds, which results in change magnitude wind erosion, as well as advantageous changes in microclimate. The roots of the plants bind the soil together, and twine with other roots, forming a more solid mass that is less susceptible to both water and wind erosion. The removal of vegetation increases the rate of surface erosion.29TopographyThe topography of the land determines the velocity at which surface runoff will flow, which in turn determines the erosivity of the runoff. Longer, steeper slopes (especially those without adequate vegetative cover) are more susceptible to very high rates of erosion during heavy rains than shorter, less steep slopes. Steeper terrain is also more prone to mudslides, landslides, and other forms of gravitational erosion processes