In biology, a population is all the organisms of the same group or species, which live in a particular geographical area, have the capability of interbreeding. The area of a sexual population is the area where inter-breeding is possible between any pair within the area, where the probability of interbreeding is greater than the probability of cross-breeding with individuals from other areas. In sociology, population refers to a collection of humans. Demography is a social science. Population in simpler terms is the number of people in a city or town, country or world. In population genetics a sex population is a set of organisms in which any pair of members can breed together; this means that they can exchange gametes to produce normally-fertile offspring, such a breeding group is known therefore as a Gamo deme. This implies that all members belong to the same species. If the Gamo deme is large, all gene alleles are uniformly distributed by the gametes within it, the Gamo deme is said to be panmictic.
Under this state, allele frequencies can be converted to genotype frequencies by expanding an appropriate quadratic equation, as shown by Sir Ronald Fisher in his establishment of quantitative genetics. This occurs in Nature: localization of gamete exchange – through dispersal limitations, preferential mating, cataclysm, or other cause – may lead to small actual Gamo demes which exchange gametes reasonably uniformly within themselves but are separated from their neighboring Gamo demes. However, there may be low frequencies of exchange with these neighbors; this may be viewed as the breaking up of a large sexual population into smaller overlapping sexual populations. This failure of panmixia leads to two important changes in overall population structure: the component Gamo demos vary in their allele frequencies when compared with each other and with the theoretical panmictic original; the overall rise in homozygosity is quantified by the inbreeding coefficient. Note that all homozygotes are increased in frequency – both the deleterious and the desirable.
The mean phenotype of the Gamo demes collection is lower than that of the panmictic original –, known as inbreeding depression. It is most important to note, that some dispersion lines will be superior to the panmictic original, while some will be about the same, some will be inferior; the probabilities of each can be estimated from those binomial equations. In plant and animal breeding, procedures have been developed which deliberately utilize the effects of dispersion, it can be shown that dispersion-assisted selection leads to the greatest genetic advance, is much more powerful than selection acting without attendant dispersion. This is so for both autogamous Gamo demes. In ecology, the population of a certain species in a certain area can be estimated using the Lincoln Index. According to the United States Census Bureau the world's population was about 7.55 billion in 2019 and that the 7 billion number was surpassed on 12 March 2012. According to a separate estimate by the United Nations, Earth’s population exceeded seven billion in October 2011, a milestone that offers unprecedented challenges and opportunities to all of humanity, according to UNFPA, the United Nations Population Fund.
According to papers published by the United States Census Bureau, the world population hit 6.5 billion on 24 February 2006. The United Nations Population Fund designated 12 October 1999 as the approximate day on which world population reached 6 billion; this was about 12 years after world population reached 5 billion in 1987, 6 years after world population reached 5.5 billion in 1993. The population of countries such as Nigeria, is not known to the nearest million, so there is a considerable margin of error in such estimates. Researcher Carl Haub calculated that a total of over 100 billion people have been born in the last 2000 years. Population growth increased as the Industrial Revolution gathered pace from 1700 onwards; the last 50 years have seen a yet more rapid increase in the rate of population growth due to medical advances and substantial increases in agricultural productivity beginning in the 1960s, made by the Green Revolution. In 2017 the United Nations Population Division projected that the world's population will reach about 9.8 billion in 2050 and 11.2 billion in 2100.
In the future, the world's population is expected to peak, after which it will decline due to economic reasons, health concerns, land exhaustion and environmental hazards. According to one report, it is likely that the world's population will stop growing before the end of the 21st century. Further, there is some likelihood that population will decline before 2100. Population has declined in the last decade or two in Eastern Europe, the Baltics and in the Commonwealth of Independent States; the population pattern of less-developed regions of the world in recent years has been marked by increasing birth rates. These followed an earlier sharp reduction in death rates; this transition from high birth and death rates to low birth
The Ogallala Aquifer is a shallow water table aquifer surrounded by sand, silt and gravel located beneath the Great Plains in the United States. One of the world's largest aquifers, it underlies an area of 174,000 sq mi in portions of eight states, it was named in 1898 by geologist N. H. Darton from its type locality near the town of Ogallala, Nebraska; the aquifer is part of the High Plains Aquifer System, rests on the Ogallala Formation, the principal geologic unit underlying 80% of the High Plains. Large scale extraction for agricultural purposes started after World War II due to center pivot irrigation and to the adaptation of automotive engines for groundwater wells. Today about 27% of the irrigated land in the entire United States lies over the aquifer, which yields about 30% of the ground water used for irrigation in the United States; the aquifer is at risk for pollution. Since 1950, agricultural irrigation has reduced the saturated volume of the aquifer by an estimated 9%. Once depleted, the aquifer will take over 6,000 years to replenish through rainfall.
The aquifer system supplies drinking water to 82% of the 2.3 million people who live within the boundaries of the High Plains study area. The deposition of aquifer material dates back two to six million years, from the late Miocene to early Pliocene ages when the southern Rocky Mountains were still tectonically active. From the uplands to the west and streams cut channels in a west to east or southeast direction. Erosion of the Rockies provided alluvial and aeolian sediment that filled the ancient channels and covered the entire area of the present-day aquifer, forming the water-bearing Ogallala Formation. In that respect, the process is similar to those prevailing in other modern rivers of the area, such as the Kansas River and its tributaries; the major differences are depth. The depth of the Ogallala varies with the shape of then-prevailing surface, being deepest where it fills ancient valleys and channels; the Ogallala Formation consists of coarse sedimentary rocks in its deeper sections, which transition upward into finer-grained material.
The water-saturated thickness of the Ogallala Formation ranges from a few feet to more than 1,000 feet. Its deepest part is 1200 ft. and is greater in the Northern Plains. The depth of the water below the surface of the land ranges from 400 feet in parts of the north to between 100 and 200 feet throughout much of the south. Present-day recharge of the aquifer with fresh water occurs at an exceedingly slow rate, suggesting that much of the water in its pore spaces is paleowater, dating back to the most recent ice age and earlier. Groundwater within the Ogallala flows from west to east at an average rate of a foot per day. Hydraulic conductivity, or the ability for a fluid to move through porous material, ranges from 25 to 300 feet per day. Water quality within the Ogallala varies with the highest quality for drinking and irrigation in the northern region while the southern region had the poorest. Human and natural processes over the past 60 to 70 years, including irrigation density and nitrogen applications, have caused higher concentrations of contaminants including nitrates.
Nitrate levels meet USGS water quality standards, but continue to increase over time. This trend can impact the future groundwater sustainability for portions of the aquifer. An aquifer is a groundwater storage reservoir in the water cycle. While groundwater is a renewable source, reserves replenish slowly; the USGS has performed several studies of the aquifer, to determine what is coming in, what is leaving, what the net changes in storage are. Withdrawals from the Ogallala Aquifer for irrigation amounted to 26 km3 in 2000; as of 2005, the total depletion since before development amounted to 253,000,000 acre feet. Some estimates indicate the remaining volume could be depleted as soon as 2028. Many farmers in the Texas High Plains, which rely on the underground source, are now turning away from irrigated agriculture as they become aware of the hazards of overpumping; the rate at which recharge water enters the aquifer is limited by several factors. Much of the plains region is semiarid, with steady winds that hasten evaporation of surface water and precipitation.
In many locations, the aquifer is overlain, in the vadose zone, with a shallow layer of caliche, impermeable. However, the soil of the playa lakes is different and not lined with caliche, making these some of the few areas where the aquifer can recharge; the destruction of playas by farmers and development decreases the available recharge area. The prevalence of the caliche is due to the ready evaporation of soil moisture and the semiarid climate. Both mechanisms reduce the amount of recharge water. Recharge in the aquifer ranges from 0.024 inches per year in parts of Texas and New Mexico to 6 inches per year in south-central Kansas. The regions overlying the Ogallala Aquifer are some of the most productive regions in the United States for ranching livestock, growing corn and soybeans; the success of large-scale farming in areas that do not have adequate precipita
A county seat is an administrative center, seat of government, or capital city of a county or civil parish. The term is used in Canada, Romania and the United States. County towns have a similar function in the United Kingdom and Republic of Ireland, in Jamaica. In most of the United States, counties are the political subdivisions of a state; the city, town, or populated place that houses county government is known as the seat of its respective county. The county legislature, county courthouse, sheriff's department headquarters, hall of records and correctional facility are located in the county seat though some functions may be located or conducted in other parts of the county if it is geographically large. A county seat is but not always, an incorporated municipality; the exceptions include the county seats of counties that have no incorporated municipalities within their borders, such as Arlington County, Virginia. Ellicott City, the county seat of Howard County, is the largest unincorporated county seat in the United States, followed by Towson, the county seat of Baltimore County, Maryland.
Some county seats may not be incorporated in their own right, but are located within incorporated municipalities. For example, Cape May Court House, New Jersey, though unincorporated, is a section of Middle Township, an incorporated municipality. In some of the colonial states, county seats include or included "Court House" as part of their name. In the Canadian provinces of Prince Edward Island, New Brunswick, Nova Scotia, the term "shire town" is used in place of county seat. County seats in Taiwan are the administrative centers of the counties. There are 13 county seats in Taiwan, which are in the forms of county-administered city, urban township or rural township. Most counties have only one county seat. However, some counties in Alabama, Georgia, Kentucky, Mississippi, New Hampshire, New York, Vermont have two or more county seats located on opposite sides of the county. An example is Harrison County, which lists both Biloxi and Gulfport as county seats; the practice of multiple county seat towns dates from the days.
There have been few efforts to eliminate the two-seat arrangement, since a county seat is a source of pride for the towns involved. There are 36 counties with multiple county seats in 11 states: Coffee County, Alabama St. Clair County, Alabama Arkansas County, Arkansas Carroll County, Arkansas Clay County, Arkansas Craighead County, Arkansas Franklin County, Arkansas Logan County, Arkansas Mississippi County, Arkansas Prairie County, Arkansas Sebastian County, Arkansas Yell County, Arkansas Columbia County, Georgia Lee County, Iowa Campbell County, Kentucky Kenton County, Kentucky Essex County, Massachusetts Middlesex County, Massachusetts Plymouth County, Massachusetts Bolivar County, Mississippi Carroll County, Mississippi Chickasaw County, Mississippi Harrison County, Mississippi Hinds County, Mississippi Jasper County, Mississippi Jones County, Mississippi Panola County, Mississippi Tallahatchie County, Mississippi Yalobusha County, Mississippi Jackson County, Missouri Hillsborough County, New Hampshire Seneca County, New York Bennington County, Vermont In New England, the town, not the county, is the primary division of local government.
Counties in this region have served as dividing lines for the states' judicial systems. Connecticut and Rhode Island have no county level of thus no county seats. In Vermont and Maine the county seats are designated shire towns. County government consists only of a Superior Court and Sheriff, both located in the respective shire town. Bennington County has two shire towns. In Massachusetts, most government functions which would otherwise be performed by county governments in other states are performed by town or city governments; as such, Massachusetts has dissolved many of its county governments, the state government now operates the registries of deeds and sheriff's offices in those counties. In Virginia, a county seat may be an independent city surrounded by, but not part of, the county of which it is the administrative center. Two counties in South Dakota have their county seat and government services centered in a neighboring county, their county-level services are provided by Fall River Tripp County, respectively.
In Louisiana, divided into parishes rather than counties, county seats are referred to as parish seats. Alaska is divided into boroughs rather than counties; the Unorganized Borough, which covers 49 % of Alaska's area, has equivalent. The state with the most counties is Texas, with 254, the state with the fewest counties is Delaware, with 3. County seat war Administrative center County town, administrative centres in Ireland and the UK Chef-lieu, administrative centres in Algeria, Luxembourg, France and Tunisia Municipality, equivalent to county in many c
Aeolian processes spelled eolian or æolian, pertain to wind activity in the study of geology and weather and to the wind's 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 and a large supply of unconsolidated sediments. 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 keeper of the winds. Wind erodes the Earth's surface 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. Half of Earth's 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 and provide the shine. Deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are small, but may be up to several kilometers in diameter. Wind-driven grains abrade landforms. 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 been cut, sometimes polished, by the abrasive action of wind. Sculpted landforms, called yardangs, are up to tens of meters high and kilometers long and are forms that have been streamlined by desert winds; the famous Great Sphinx of Giza in Egypt may be a modified yardang. Major global aeolian dust movements thought to influence and/or be influenced by weather and climate variation: From Sahara averaged 182 million tons of dust each year between 2007 and 2011 and carry it past the western edge of the Sahara at longitude 15W.
Variation: 86%. Destination: 132 mln tons cross the Atlantic, 27.7 mln tons fall in Amazon Basin, 43 mln make it to the Caribbean. Texas and Florida receive the dust. Events have become far more common in recent decades. Source: NASA's Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data. Harmattan winter dust storms in West Africa occur blowing dust to the ocean. Gobi Desert to Korea, Japan and Western USA. See Asian dust. Thar Desert pre-monsoon towards Delhi, Uttar Pradesh, Indo-Gangetic Plain. See 2018 Indian dust storms. Shamal June–July winds blowing dust in north to south in Saudi Arabia, Iraq, UAE, parts of Pakistan. Haboob dust storms in Sudan, Arizona associated with monsoon. Khamsin dust from Libya and Levant in Spring associated with extratropical cyclones. Dust Bowl event in USA, carried sand eastward. 5500 tons were deposited in Chicago area. Sirocco sandy winds from Africa/Sahara blowing north into South Europe. Kalahari Desert blowing east to southern Indian Ocean and Australia.
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 Earth's 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 skips. Saltation 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; the grain may hit larger grains that are too heavy to hop, but that 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 when rain passes through it; this cooler and denser air sinks toward the desert surface.
When it reaches the ground, the air is deflected forward and sweeps up surface debris in its turbulence as a dust storm. Crops, people and even climates are affected by dust storms; some dust storms are intercontinental, a few may circle the globe, they may engulf entire planets. When the Mariner 9 spacecraft entered its orbit around Mars in 1971, a dust storm lasting one month covered the entire planet, thus delaying the task of photo-mapping the planet's surface. Most of the dust carried by dust storms is in the form of silt-size particles. Deposits of this windblown silt are known as loess; the thickest known deposit of loess, 335 meters, is on the Loess Plateau in China. This same Asian dust is blown for thousands of miles, forming deep beds in places as far away as Hawaii. In Europe and in the Americas, accumulations of loess are from 20 to 30 meters thick; the soils developed on loess are highly productive for agriculture. Aeolian transport from deserts plays an important role in ecosystems globally, e.g. by transport of minerals from the Sahara to the Ama
Women's National Basketball Association
The Women's National Basketball Association is a professional basketball league in the United States. It is composed of twelve teams; the league was founded on April 24, 1996, as the women's counterpart to the National Basketball Association, league play started in 1997. The regular season is played from May to September with the All Star game being played midway through the season in July and the WNBA Finals at the end of September until the beginning of October. Five WNBA teams have direct NBA counterparts and play in the same arena: the Indiana Fever, Los Angeles Sparks, Minnesota Lynx, Phoenix Mercury, Washington Mystics; the Atlanta Dream, Chicago Sky, Connecticut Sun, Dallas Wings, Las Vegas Aces, New York Liberty, Seattle Storm do not share an arena with a direct NBA counterpart, although four of the seven share a market with an NBA counterpart, the Storm shared an arena and market with an NBA team at the time of its founding. The Dream, the Sky, the Sun, the Wings, the Aces, the Sparks, the Storm are all independently owned.
The creation of the WNBA was approved by the NBA Board of Governors on April 24, 1996, announced at a press conference with Rebecca Lobo, Lisa Leslie, Sheryl Swoopes in attendance. The new WNBA had to compete with the formed American Basketball League, another professional women's basketball league that began play in 1996; the WNBA began with eight teams: the Charlotte Sting, Cleveland Rockers, Houston Comets and New York Liberty in the Eastern Conference. While not the first major women's professional basketball league in the United States, the WNBA is the only league to receive full backing of the NBA; the WNBA logo, "Logo Woman", was selected out of 50 different designs. On the heels of a much-publicized gold medal run by the 1996 USA Basketball Women's National Team at the 1996 Summer Olympic Games, the WNBA began its first season on June 21, 1997 to little fanfare; the first WNBA game featured the New York Liberty facing the Los Angeles Sparks in Los Angeles. The game was televised nationally in the United States on the NBC television network.
At the start of the 1997 season, the WNBA had television deals in place with NBC, the Walt Disney Company and Hearst Corporation joint venture channels, ESPN and Lifetime Television Network, respectively. Penny Toler scored the league's first point; the WNBA centered its marketing campaign, dubbed "We Got Next", around stars Rebecca Lobo, Lisa Leslie and Sheryl Swoopes. In the league's first season, Leslie's Los Angeles Sparks underperformed and Swoopes sat out much of the season due to her pregnancy; the WNBA's true star in 1997 was Swoopes' teammate on the Houston Comets. The Comets defeated Lobo's New York Liberty in the first WNBA Championship game; the initial "We Got Next" advertisement ran before each WNBA season until it was replaced with the "We Got Game" campaign. Two teams were added in 1998 and two more in 1999, bringing the number of teams in the league up to twelve; the 1999 season began with a collective bargaining agreement between players and the league, marking the first collective bargaining agreement to be signed in the history of women's professional sports.
The WNBA announced in 1999 that it would add four more team for the 2000 season, bringing the league up to 16 teams, with WNBA President Val Ackerman discussing expansion: "This won't be the end of it. We expect to keep growing the league."In 1999, the league's chief competition, the American Basketball League, folded. Many of the ABL's star players, including several Olympic gold medalists and a number of standout college performers joined the rosters of WNBA teams and, in so doing, enhanced the overall quality of play in the league; when a lockout resulted in an abbreviated NBA season, the WNBA saw faltering TV viewership. On May 23, 2000, the Houston Comets became the first WNBA team to be invited to the White House Rose Garden. Before this invitation, only men's sports teams had traveled to the White House. At the end of the 2000 season, the Houston Comets won their fourth championship, capturing every title since the league's inception. Led by the "Big Three" of Sheryl Swoopes, Tina Thompson, four-time Finals MVP Cynthia Cooper, the Comets dominated every team in the league.
Under head coach Van Chancellor, the team posted a 98–24 record through their first four seasons. After 2000, Cooper retired from the league and the Comets dynasty came to an end; the top contender in the 2001 season was the Los Angeles Sparks. Led by Lisa Leslie, the Sparks posted a regular-season record of 28–4, they advanced to their first WNBA Finals and swept the Charlotte Sting. Looking to repeat in 2002, the Sparks again made a strong run toward the postseason, going 25–7 in the regular season under head coach Michael Cooper of the Los Angeles Lakers. Again, Leslie dominated opponents throughout the Playoffs, leading the Sparks to a perfect 6–0 record through all three rounds, beating the New York Liberty in the 2002 Finals. Teams and the league were collectively owned by the NBA until the end of 2002, when the NBA sold WNBA teams either to their NBA counterparts in the same city or to a third party, as a result of the dot-com bubble; this led to two teams moving: Utah moved to San Antonio, Orlando moved to Connecticut and became the first WNBA team to be
Llano Estacado translated as Staked Plains, is a region in the Southwestern United States that encompasses parts of eastern New Mexico and northwestern Texas. One of the largest mesas or tablelands on the North American continent, the elevation rises from 3,000 feet in the southeast to over 5,000 feet in the northwest, sloping uniformly at about 10 feet per mile; the Llano Estacado lies at the southern end of the Western High Plains ecoregion of the Great Plains of North America. The Canadian River forms the Llano's northern boundary, separating it from the rest of the High Plains. To the east, the Caprock Escarpment, a precipitous cliff about 300 feet high, lies between the Llano and the red Permian plains of Texas; the Llano has no natural southern boundary, instead blending into the Edwards Plateau near Big Spring, Texas. This geographic area stretches about 250 miles north to south, 150 miles east to west, a total area of some 37,500 square miles, larger than Indiana and 12 other states.
It covers all or part of 33 Texas counties and four New Mexico counties. Some years, a National Weather Service dust storm warning is issued in parts of Texas due to a dust storm originating from the area or from the adjacent lower part of the Southwestern Tablelands ecological region; the landscape is dotted by numerous small playa lakes, depressions that seasonally fill with water and provide habitat for waterfowl. The Llano Estacado has a "cold semiarid" climate, characterized by long, hot summers and cold winters. Rainfall is low. High summer temperatures mean most of the small amount of precipitation is lost to evaporation, making dryland farming difficult; the Texas State Historical Society states it covers all or part of 33 Texas counties, six fewer than as depicted by a US Geological Survey map, four New Mexico counties. As depicted by a US Geological Survey map, the Llano Estacado includes all or part of these Texas counties: It includes all or part of the following New Mexico counties: Curry Lea Quay Roosevelt Several interstate highways serve the Llano Estacado.
Interstate 40 crosses the northern portion from east of Amarillo to New Mexico. Interstate 27 runs north-south between Amarillo and Lubbock, while Interstate 20 passes through the southern portion of the Llano Estacado west of Midland and Odessa. Spanish conquistador Francisco Coronado, the first European to traverse this "sea of grass" in 1541, described it as follows: I reached some plains so vast, that I did not find their limit anywhere I went, although I traveled over them for more than 300 leagues... with no more land marks than if we had been swallowed up by the sea... There was not bit of rising ground, nor a tree, nor a shrub, nor anything to go by. In the early 18th century, the Comanches expanded their territory into the Llano Estacado, displacing the Apaches who had lived there; the region became part of the Comancheria, a Comanche stronghold until the final defeat of the tribe in the late 19th century. The Comanche war trail extended from Llano Estacado to the Rio Grande into Chihuahua, "the trail ran southwesterly through Big Spring to the Horsehead Crossing of the Pecos River forked southward to the Comanche Springs where it divided, one part of the trail crossing the great river near Boquillas and the other at Presidio."Rachel Plummer, while a captive of the Comanche in 1836, mentioned the "table lands between Austin and Santa Fe".
Robert Neighbors and Rip Ford, guided by Buffalo Hump, blazed the "upper route" trail from San Antonio to El Paso in 1849 for emigrants during the California Gold Rush, "... travelling across an elevated plateau covered by rock..."After his 1852 expedition to explore the headwaters of the Red and Colorado Rivers, General Randolph Marcy wrote: " a tree, shrub, or any other herbage to intercept the vision... the total absence of water causes all animals to shun it: the Indians do not venture to cross it except at two or three places." In his report for the United States Army: When we were upon the high table-land, a view presented itself as boundless as the ocean. Not a tree, shrub, or any other object, either animate or inanimate, relieved the dreary monotony of the prospect; the great Sahara of North America. It is a region as vast and trackless as the ocean—a land where no man, either savage or civilized permanently abides... a treeless, desolate waste of uninhabitable solitude, which always has been, must continue uninhabited forever.
During the 1854 Marcy-Neighbors expedition, Dr. George Getz Shumard noted, "Beyond the mountain appeared a line of high bluffs which in the distance looked like clouds floating upon the horizon."Herman Lehmann was captured by the Apache in 1870 and described the Llano Estacado as "the country was open, but not a desert". Robert G. Carter described it in 1871 while pursuing Quanah Parker with Ranald S. Mackenzie, "... all were over and out of the canyon upon what appeared to be a vast illimitable expanse of prairie. As far as the eye could reach, not a bush or tree, a twig or stone, not an object of any kind or a living thing, was in sight, it stretched out before us-one uninterrupted plain, only to be compared to the ocean in its vastness."In August 1872, Mackenzie was the first to successf
A city is a large human settlement. Cities have extensive systems for housing, sanitation, land use, communication, their density facilitates interaction between people, government organizations and businesses, sometimes benefiting different parties in the process. City-dwellers have been a small proportion of humanity overall, but following two centuries of unprecedented and rapid urbanization half of the world population now lives in cities, which has had profound consequences for global sustainability. Present-day cities form the core of larger metropolitan areas and urban areas—creating numerous commuters traveling towards city centers for employment and edification. However, in a world of intensifying globalization, all cities are in different degree connected globally beyond these regions; the most populated city proper is Chongqing while the most populous metropolitan areas are the Greater Tokyo Area, the Shanghai area, Jabodetabek. The cities of Faiyum and Varanasi are among those laying claim to longest continual inhabitation.
A city is distinguished from other human settlements by its great size, but by its functions and its special symbolic status, which may be conferred by a central authority. The term can refer either to the physical streets and buildings of the city or to the collection of people who dwell there, can be used in a general sense to mean urban rather than rural territory. A variety of definitions, invoking population, population density, number of dwellings, economic function, infrastructure, are used in national censuses to classify populations as urban. Common population definitions for a city range between 1,500 and 50,000 people, with most U. S. states using a minimum between 5,000 inhabitants. However, some jurisdictions set no such minimums. In the United Kingdom, city status is awarded by the government and remains permanently, resulting in some small cities, such as Wells and St Davids. According to the "functional definition" a city is not distinguished by size alone, but by the role it plays within a larger political context.
Cities serve as administrative, commercial and cultural hubs for their larger surrounding areas. Examples of settlements called city which may not meet any of the traditional criteria to be named such include Broad Top City and City Dulas, Anglesey, a hamlet; the presence of a literate elite is sometimes included in the definition. A typical city has professional administrators and some form of taxation to support the government workers; the governments may be based on heredity, military power, work projects such as canal building, food distribution, land ownership, commerce, finance, or a combination of these. Societies that live in cities are called civilizations; the word city and the related civilization come, via Old French, from the Latin root civitas meaning citizenship or community member and coming to correspond with urbs, meaning city in a more physical sense. The Roman civitas was linked with the Greek "polis"—another common root appearing in English words such as metropolis. Urban geography deals both with their internal structure.
Town siting has varied through history according to natural, technological and military contexts. Access to water has long been a major factor in city placement and growth, despite exceptions enabled by the advent of rail transport in the nineteenth century, through the present most of the world's urban population lives near the coast or on a river. Urban areas as a rule cannot produce their own food and therefore must develop some relationship with a hinterland which sustains them. Only in special cases such as mining towns which play a vital role in long-distance trade, are cities disconnected from the countryside which feeds them. Thus, centrality within a productive region influences siting, as economic forces would in theory favor the creation of market places in optimal mutually reachable locations; the vast majority of cities have a central area containing buildings with special economic and religious significance. Archaeologists refer to this area by the Greek term temenos; these spaces reflect and amplify the city's centrality and importance to its wider sphere of influence.
Today cities have downtown, sometimes coincident with a central business district. Cities have public spaces where anyone can go; these include owned spaces open to the public as well as forms of public land such as public domain and the commons. Western philosophy since the time of the Greek agora has considered physical public space as the substrate of the symbolic public sphere. Public art adorns public spaces. Parks and other natural sites within cities provide residents with relief from the hardness and regularity of typical built environments. Urban structure follows one or more basic patterns: geomorphic, concentric and curvilinear. Physical environment constrains the form in which a city is built. If located on a mountainside, urban structure may rely on winding roads, it may be adapted to its means of subsistence. And it may be set up for optimal defense given the surrounding landscape. Beyond these "geomorphi