Feldspars are a group of rock-forming tectosilicate minerals that make up about 40% of the Earths continental crust. Feldspars crystallize from magma as veins in both intrusive and extrusive rocks and are present in many types of metamorphic rock. Rock formed almost entirely of plagioclase feldspar is known as anorthosite. Feldspars are found in types of sedimentary rocks. The name feldspar derives from the German Feldspat, a compound of the words Feld and Spat, the change from Spat to -spar was influenced by the English word spar, a synonym for mineral. Feldspathic refers to materials that contain feldspar, the alternate spelling, has largely fallen out of use. This group of minerals consists of tectosilicates, solid solutions between albite and anorthite are called plagioclase, or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar, the alkali feldspars are as follows, orthoclase —KAlSi3O8 sanidine —AlSi3O8 microcline —KAlSi3O8 anorthoclase —AlSi3O8 Sanidine is stable at the highest temperatures, and microcline at the lowest.
Perthite is a texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye, microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Barium feldspars are considered alkali feldspars, barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. The barium feldspars are monoclinic and include the following, celsian—BaAl2Si2O8 hyalophane—4O8 The plagioclase feldspars are triclinic, the immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae, chemical weathering of feldspars results in the formation of clay minerals.
About 20 million tonnes of feldspar were produced in 2010, mostly by three countries, Italy and China, Feldspar is a common raw material used in glassmaking, and to some extent as a filler and extender in paint and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, in ceramics, the alkalis in feldspar act as a flux, lowering the melting temperature of a mixture. Fluxes melt at a stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and other uses, such as fillers, accounted for the remainder
Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of 357,021 square kilometres, with about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular destination in the world. Germanys capital and largest metropolis is Berlin, while its largest conurbation is the Ruhr, other major cities include Hamburg, Cologne, Stuttgart, Düsseldorf and Leipzig. Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity, a region named Germania was documented before 100 AD. During the Migration Period the Germanic tribes expanded southward, beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation, in 1871, Germany became a nation state when most of the German states unified into the Prussian-dominated German Empire.
After World War I and the German Revolution of 1918–1919, the Empire was replaced by the parliamentary Weimar Republic, the establishment of the national socialist dictatorship in 1933 led to World War II and the Holocaust. After a period of Allied occupation, two German states were founded, the Federal Republic of Germany and the German Democratic Republic, in 1990, the country was reunified. In the 21st century, Germany is a power and has the worlds fourth-largest economy by nominal GDP. As a global leader in industrial and technological sectors, it is both the worlds third-largest exporter and importer of goods. Germany is a country with a very high standard of living sustained by a skilled. It upholds a social security and universal health system, environmental protection. Germany was a member of the European Economic Community in 1957. It is part of the Schengen Area, and became a co-founder of the Eurozone in 1999, Germany is a member of the United Nations, NATO, the G8, the G20, and the OECD.
The national military expenditure is the 9th highest in the world, the English word Germany derives from the Latin Germania, which came into use after Julius Caesar adopted it for the peoples east of the Rhine. This in turn descends from Proto-Germanic *þiudiskaz popular, derived from *þeudō, descended from Proto-Indo-European *tewtéh₂- people, the discovery of the Mauer 1 mandible shows that ancient humans were present in Germany at least 600,000 years ago. The oldest complete hunting weapons found anywhere in the world were discovered in a mine in Schöningen where three 380, 000-year-old wooden javelins were unearthed
Regolith is a layer of loose, heterogeneous superficial material covering solid rock. It includes dust, broken rock, and other related materials and is present on Earth, the Moon, some asteroids, the term regolith combines two Greek words, rhegos and lithos, rock. Merrill first defined the term in 1897, writing, In places this covering is made up of material originating through rock-weathering or plant growth in situ, in other instances it is of fragmental and more or less decomposed matter drifted by wind, water or ice from other sources. This entire mantle of unconsolidated material, whatever its nature or origin and organic components derived from it. Regolith can vary from being essentially absent to hundreds of metres in thickness and its age can vary from instantaneous to hundreds of millions of years old. Regolith on Earth originates from weathering and biological processes, if it contains a significant proportion of biological compounds it is conventionally referred to as soil. People call various types of earthly regolith by such names as dirt, gravel, Regolith is important to engineers constructing buildings and other civil works.
The mechanical properties of regolith vary considerably and need to be documented if the construction is to withstand the rigors of use, Regolith may host many mineral deposits, for example mineral sands, calcrete uranium, and lateritic nickel deposits, among others. Elsewhere, understanding regolith properties, especially geochemical composition, is critical to geochemical and geophysical exploration for mineral deposits beneath it, the regolith is an important source of construction material, including sand, crushed stone and gypsum. The regolith is the zone through which aquifers are recharged and through which aquifer discharge occurs, many aquifers, such as alluvial aquifers, occur entirely within regolith. The composition of the regolith can strongly influence water composition through the presence of salts, Regolith covers almost the entire lunar surface, bedrock protruding only on very steep-sided crater walls and the occasional lava channel. The impact of micrometeoroids, sometimes travelling faster than 96,000 km/h and this melting and refreezing welds particles together into glassy, jagged-edged agglutinates, reminiscent of tektites found on Earth.
The regolith is generally from 4 to 5 m thick in mare areas, below this true regolith is a region of blocky and fractured bedrock created by larger impacts, which is often referred to as the megaregolith. The density of regolith at the Apollo 15 landing site averages approximately 1.35 g/cm3 for the top 30 cm, and it is approximately 1. 85g/cm3 at a depth of 60 cm. The term lunar soil is used interchangeably with lunar regolith but typically refers to the finer fraction of regolith. Some have argued that the soil is not correct in reference to the Moon because soil is defined as having organic content. However, standard usage among lunar scientists is to ignore that distinction, lunar dust generally connotes even finer materials than lunar soil, the fraction which is less than 30 micrometers in diameter. The average chemical composition of regolith might be estimated from the concentration of elements in lunar soil
Dust is fine particles of matter. It generally consists of particles in the atmosphere that come from sources such as soil, dust lifted by weather, volcanic eruptions. House dust mites are present indoors wherever humans live, positive tests for dust mite allergies are extremely common among people with asthma. Dust mites are microscopic arachnids whose primary food is dead skin cells. They and their feces and other allergens they produce are major constituents of house dust and they are generally found on the floor and other surfaces until disturbed. It could take somewhere between twenty minutes and two hours for dust mites to settle back down out of the air, Dust mites are a nesting species that prefers a dark and humid climate. They flourish in mattresses, upholstered furniture, and carpets and their feces include enzymes that are released upon contact with a moist surface, which can happen when a person inhales, and these enzymes can kill cells within the human body. House dust mites did not become a problem until humans began to use textiles, such as western style blankets and clothing.
Atmospheric or wind-borne dust, known as aeolian dust, comes from arid and dry regions where high velocity winds are able to remove mostly silt-sized material, Dust in the atmosphere is produced by saltation and sandblasting of sand-sized grains, and it is transported through the troposphere. This airborne dust is considered an aerosol and once in the atmosphere, saharan dust in particular can be transported and deposited as far as the Caribbean and the Amazon basin, and may affect air temperatures, cause ocean cooling, and alter rainfall amounts. Dust in the Middle East has been a historic phenomenon, because of climate change and the escalating process of desertification, the problem has worsened dramatically. As a multi-factor phenomenon, there is not yet a consensus on the sources or potential solutions to the problem. In Iran, the dust is already affecting more than 5 million people directly, in the province of Khuzestan it has led to the severe reduction of air quality. The amount of pollutants in the air has surpassed more than 50 times the normal level several times in a year, initiatives such as Project-Dust have been established to directly study the Middle Eastern dust.
Dust kicked up by vehicles traveling on roads may make up 33% of air pollution, road dust consists of deposits of vehicle exhausts and industrial exhausts, particles from tire and brake wear, dust from paved roads or potholes, and dust from construction sites. Road dust is a significant source contributing to the generation and release of particulate matter into the atmosphere. Control of road dust is a significant challenge in urban areas, road dust may be suppressed by mechanical methods like street sweeper vehicles equipped with vacuum cleaners, vegetable oil sprays, or with water sprayers. Improvements in automotive engineering have reduced the amount of PM10s produced by road traffic, coal dust is responsible for the lung disease known as pneumoconiosis, including black lung disease that occurs among coal miners
Loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. It covers about 10% of the Earths surface and it is usually homogeneous and highly porous and is traversed by vertical capillaries that permit the sediment to fracture and form vertical bluffs. It was first applied to Rhine River valley loess about 1821, Loess is homogeneous, friable, pale yellow or buff, slightly coherent, typically non-stratified and often calcareous. Loess grains are angular with little polishing or rounding and composed of crystals of quartz, mica, Loess can be described as a rich, dust-like soil. Loess deposits may become thick, more than a hundred meters in areas of China. It generally occurs as a deposit that covers areas of hundreds of square kilometers. Loess often stands in either steep or vertical faces, because the grains are angular, loess will often stand in banks for many years without slumping. This soil has a characteristic called vertical cleavage which makes it easily excavated to form cave dwellings, in several areas of the world, loess ridges have formed that are aligned with the prevailing winds during the last glacial maximum.
These are called paha ridges in America and greda ridges in Europe, the form of these loess dunes has been explained by a combination of wind and tundra conditions. Loess comes from the German Löss or Löß, and ultimately from Alemannic lösch meaning loose as named by peasants, the term Löß was first described in Central Europe by Karl Cäsar von Leonhard who reported yellowish brown, silty deposits along the Rhine valley near Heidelberg. Charles Lyell brought this term into usage by observing similarities between loess and loess derivatives along the loess bluffs in the Rhine and Mississippi. At that time it was thought that the yellowish brown silt-rich sediment was of fluvial origin being deposited by the large rivers. It wasnt until the end of the 19th century that the origin of loess was recognized. A tremendous number of papers have been published since then, focusing on the formation of loess and on loess/palaeosol sequences as archives of climate and these water conservation works were carried out extensively in China and the research of Loess in China has been continued since 1954.
Much effort was put into the setting up of regional and local loess stratigraphies, and Frechen, Horváth & Gábris for the Austrian and Hungarian loess stratigraphy, respectively. During the autumn and winter, when melting of the icesheets and icecaps ceased, as a consequence, large parts of the formerly submerged and unvegetated floodplains of these braided rivers dried out and were exposed to the wind. Because these floodplains consist of sediment containing a high content of glacially ground flour-like silt and clay, they were susceptible to winnowing of their silts. Once entrained by the wind, particles were deposited downwind, the loess deposits found along both sides of the Mississippi River Alluvial Valley are a classic example of periglacial loess
A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. The primary factor that distinguishes wetlands from other forms or water bodies is the characteristic vegetation of aquatic plants. Wetlands play a number of roles in the environment, principally water purification, flood control, carbon sink, Wetlands are considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Wetlands occur naturally on every continent except Antarctica, the largest including the Amazon River basin, the West Siberian Plain, the water found in wetlands can be freshwater, brackish, or saltwater. The main wetland types include swamps, marshes and fens, and sub-types include mangrove, pocosin, the UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. International conservation efforts are being used in conjunction with the development of rapid assessment tools to people about wetland issues.
Constructed wetlands can be used to treat municipal and industrial wastewater as well as stormwater runoff and they may play a role in water-sensitive urban design. A patch of land that develops pools of water after a storm would not be considered a wetland. Wetlands have unique characteristics, they are distinguished from other water bodies or landforms based on their water level. Specifically, wetlands are characterized as having a table that stands at or near the land surface for a long enough period each year to support aquatic plants. A more concise definition is a community composed of hydric soil, Wetlands have been described as ecotones, providing a transition between dry land and water bodies. In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. A wetland is an ecosystem that arises when inundation by water produces soils dominated by anaerobic processes, There are four main kinds of wetlands – marsh, swamp and fen.
Some experts recognize wet meadows and aquatic ecosystems as additional wetland types, the largest wetlands in the world include the swamp forests of the Amazon and the peatlands of Siberia. Under the Ramsar international wetland conservation treaty, wetlands are defined as follows, Article 2.1, may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands. Although the general definition given above applies around the world, each county, Wetlands generally include swamps, marshes and similar areas. This definition has been used in the enforcement of the Clean Water Act, some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal governments. It is not uncommon for a wetland to be dry for long portions of the growing season, the most important factor producing wetlands is flooding
In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, 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 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, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, 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, 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
A forest is a large area dominated by trees. Hundreds of more precise definitions of forest are used throughout the world, incorporating factors such as density, tree height, land use, legal standing. According to the widely used Food and Agriculture Organization definition, forests covered four billion hectares or approximately 30 percent of the land area in 2006. Forests are the dominant terrestrial ecosystem of Earth, and are distributed across the globe, Forests account for 75% of the gross primary productivity of the Earths biosphere, and contain 80% of the Earths plant biomass. Forests at different latitudes and elevations form distinctly different ecozones, boreal forests near the poles, tropical forests near the equator, higher elevation areas tend to support forests similar to those at higher latitudes, and amount of precipitation affects forest composition. Human society and forests influence each other in both positive and negative ways, Forests provide ecosystem services to humans and serve as tourist attractions.
Forests can affect peoples health, human activities, including harvesting forest resources, can negatively affect forest ecosystems. Although forest is a term of common parlance, there is no universally recognised precise definition, there are three broad categories of forest definitions in use, land use, and land cover. Land use definitions are based upon the purpose that the land serves. For example, a forest may be defined as any land that is used primarily for production of timber, land cover definitions define forests based upon the type and density of vegetation growing on the land. Such definitions typically define a forest as an area growing trees above some threshold and these thresholds are typically the number of trees per area, the area of ground under the tree canopy or the section of land that is occupied by the cross-section of tree trunks. Under such land cover definitions, and area of land only be defined as forest if it is growing trees, areas that fail to meet the land cover definition may be still included under while immature trees are establishing if they are expected to meet the definition at maturity.
Under land use definitions, there is variation on where the cutoff points are between a forest and savanna. Under some definitions, forests require high levels of tree canopy cover, from 60% to 100%, excluding savannas. Other definitions consider savannas to be a type of forest, the term was not endemic to Romance languages, and cognates in Romance languages, such as Italian foresta and Portuguese floresta, etc. are all ultimately borrowings of the French word. The exact origin of Medieval Latin foresta is obscure, uses of the word forest in English to denote any uninhabited area of non-enclosure are now considered archaic. The word was introduced by the Norman rulers of England as a term denoting an uncultivated area legally set aside for hunting by feudal nobility. These hunting forests were not necessarily wooded much, if at all, however, as hunting forests did often include considerable areas of woodland, the word forest eventually came to mean wooded land more generally
A stream is a body of water with a current, confined within a bed and banks. Streams are important as conduits in the cycle, instruments in groundwater recharge. The biological habitat in the vicinity of a stream is called a riparian zone. Given the status of the ongoing Holocene extinction, streams play an important corridor role in connecting fragmented habitats, the study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography. Brook A stream smaller than a creek, especially one that is fed by a spring or seep and it is usually small and easily forded. A brook is characterised by its shallowness and its bed being composed primarily of rocks, creek In North America and New Zealand, a small to medium-sized natural stream. Sometimes navigable by motor craft and may be intermittent, in parts of Maryland, New England, the UK and India, a tidal inlet, typically in a salt marsh or mangrove swamp, or between enclosed and drained former salt marshes or swamps.
In these cases, the stream is the stream, the course of the seawater through the creek channel at low. River A large natural stream, which may be a waterway, runnel the linear channel between the parallel ridges or bars on a shoreline beach or river floodplain, or between a bar and the shore. Tributary A contributory stream, or a stream which does not reach the sea, sometimes called a branch or fork. There are a number of names for a stream. Allt is used in Highland Scotland, beck is used in Yorkshire, Dumfriesshire, Cumbria and Lincolnshire. Bourne or winterbourne is used in the chalk downland of southern England, brook is used in the Midlands and Cheshire. Burn is used in Scotland and North East England, gill or ghyll is seen in the north of England and other areas influenced by Old Norse. Rivulet is an term encountered in Victorian era publications, stream is used in Southern England. Syke is used in lowland Scotland and Cumbria for a seasonal stream, branch is used to name streams in Maryland and Virginia.
Falls is used to name streams in Maryland, for streams/rivers which have waterfalls on them, little Gunpowder Falls and The Jones Falls are actually rivers named in this manner, unique to Maryland. Kill in New York, Pennsylvania and New Jersey comes from a Dutch language word meaning riverbed or water channel, run in Ohio, Michigan, New Jersey, Virginia, or West Virginia can be the name of a stream
The Nile is a major north-flowing river in northeastern Africa. It is generally regarded as the longest river in the world, in particular, the Nile is the primary water source of Egypt and Sudan. The Nile has two tributaries, the White Nile and Blue Nile. The White Nile is considered to be the headwaters and primary stream of the Nile itself, the Blue Nile, however, is the source of most of the water and silt. The White Nile is longer and rises in the Great Lakes region of central Africa and it flows north through Tanzania, Lake Victoria and South Sudan. The Blue Nile begins at Lake Tana in Ethiopia and flows into Sudan from the southeast, the two rivers meet just north of the Sudanese capital of Khartoum. The northern section of the river flows north almost entirely through the Sudanese desert to Egypt, ends in a large delta, Egyptian civilization and Sudanese kingdoms have depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, in the ancient Egyptian language, the Nile is called Ḥpī or Iteru, meaning river.
In Coptic, the words piaro or phiaro meaning the river come from the ancient name. The English name Nile and the Arabic names en-Nîl and an-Nîl both derive from the Latin Nilus and the Ancient Greek Νεῖλος, beyond that, the etymology is disputed. One possible etymology derives it from a Semitic Nahal, meaning river, the standard English names White Nile and Blue Nile, to refer to the rivers source, derive from Arabic names formerly applied only to the Sudanese stretches which meet at Khartoum. Above Khartoum, the Nile is known as the White Nile, at Khartoum the river is joined by the Blue Nile. The White Nile starts in equatorial East Africa, and the Blue Nile begins in Ethiopia, both branches are on the western flanks of the East African Rift. The drainage basin of the Nile covers 3,254,555 square kilometers, the source of the Nile is sometimes considered to be Lake Victoria, but the lake has feeder rivers of considerable size. It is either the Ruvyironza, which emerges in Bururi Province, Burundi, or the Nyabarongo, the two feeder rivers meet near Rusumo Falls on the Rwanda-Tanzania border.
Gish Abay is reportedly the place where the water of the first drops of the Blue Nile develop. The Nile leaves Lake Nyanza at Ripon Falls near Jinja, Uganda and it flows north for some 130 kilometers, to Lake Kyoga. For the remaining part it flows westerly through the Murchison Falls until it reaches the very northern shores of Lake Albert where it forms a significant river delta
New Orleans is a major United States port and the largest city and metropolitan area in the state of Louisiana. The population of the city was 343,829 as of the 2010 U. S. Census, the New Orleans metropolitan area had a population of 1,167,764 in 2010 and was the 46th largest in the United States. The New Orleans–Metairie–Bogalusa Combined Statistical Area, a trading area, had a 2010 population of 1,452,502. The city is named after the Duke of Orleans, who reigned as Regent for Louis XV from 1715 to 1723, as it was established by French colonists and it is well known for its distinct French and Spanish Creole architecture, as well as its cross-cultural and multilingual heritage. New Orleans is famous for its cuisine and its celebrations and festivals, most notably Mardi Gras. The city is referred to as the most unique in the United States. New Orleans is located in southeastern Louisiana, straddling the Mississippi River, the city and Orleans Parish are coterminous. The city and parish are bounded by the parishes of St.
Tammany to the north, St. Bernard to the east, Plaquemines to the south, and Jefferson to the south and west. Lake Pontchartrain, part of which is included in the city limits, lies to the north, before Hurricane Katrina, Orleans Parish was the most populous parish in Louisiana. As of 2015, it ranks third in population, trailing neighboring Jefferson Parish, La Nouvelle-Orléans was founded May 7,1718, by the French Mississippi Company, under the direction of Jean-Baptiste Le Moyne de Bienville, on land inhabited by the Chitimacha. It was named for Philippe II, Duke of Orléans, who was Regent of the Kingdom of France at the time and his title came from the French city of Orléans. The French colony was ceded to the Spanish Empire in the Treaty of Paris, during the American Revolutionary War, New Orleans was an important port for smuggling aid to the rebels, transporting military equipment and supplies up the Mississippi River. Bernardo de Gálvez y Madrid, Count of Gálvez successfully launched a campaign against the British from the city in 1779.
New Orleans remained under Spanish control until 1803, when it reverted briefly to French oversight, nearly all of the surviving 18th-century architecture of the Vieux Carré dates from the Spanish period, the most notable exception being the Old Ursuline Convent. Napoleon sold Louisiana to the United States in the Louisiana Purchase in 1803, the city grew rapidly with influxes of Americans, French and Africans. Later immigrants were Irish and Italians, Major commodity crops of sugar and cotton were cultivated with slave labor on large plantations outside the city. The Haitian Revolution ended in 1804 and established the republic in the Western Hemisphere. It had occurred several years in what was the French colony of Saint-Domingue
Aeolian processes, spelled eolian or æolian, pertain to wind activity in the study of geology and weather and specifically to the winds ability to shape the surface of the Earth. Winds may erode and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture, although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts. The term is derived from the name of the Greek god Aeolus, wind erodes the Earths surface by deflation and by abrasion. Regions which experience intense and sustained erosion are called deflation zones, most aeolian deflation zones are composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. Almost half of Earths desert surfaces are stony deflation zones, the rock mantle in desert pavements protects the underlying material from deflation. A dark, shiny stain, called desert varnish or rock varnish, is found on the surfaces of some desert rocks that have been exposed at the surface for a long period of time.
Manganese, iron oxides and clay minerals form most varnishes, deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are generally small, but may be up to kilometers in diameter. In parts of Antarctica wind-blown snowflakes that are technically sediments have caused abrasion of exposed rocks, grinding by particles carried in the wind creates grooves or small depressions. Ventifacts are rocks which have cut, and sometimes polished. Sculpted landforms, called yardangs, are up to tens of meters high, the famous Great Sphinx of Giza in Egypt may be a modified yardang. Particles are transported by winds through suspension and creeping along the ground, small particles may be held in the atmosphere in suspension. Upward currents of air support the weight of suspended particles and hold them indefinitely in the surrounding air, typical winds near Earths surface suspend particles less than 0.2 millimeters in diameter and scatter them aloft as dust or haze.
Saltation is downwind movement of particles in a series of jumps or skips, saltation normally lifts sand-size particles no more than one centimeter above the ground and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains that jump up to continue the saltation, the grain may hit larger grains that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains. Surface creep accounts for as much as 25 percent of grain movement in a desert, aeolian turbidity currents are better known as dust storms. Air over deserts is cooled significantly when rain passes through it and this cooler and denser air sinks toward the desert surface. When it reaches the ground, the air is deflected forward, people and possibly even climates are affected by dust storms