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Barrier Island

Barrier island

In geography, a bar is a linear shoaling landform feature within a body of water. Bars tend to be long and narrow (linear) and develop where a current (or waves) promote deposition of particles, resulting in localized shallowing (shoaling) of the water. Bars can appear in the sea, in a lake, or in a river. They are typically composed of sand, although could be of any particulate matter that the moving water has access to and is capable of shifting around (for example, soil, silt, gravel, cobble, shingle, or even boulders). The size of the particles comprising a bar is related to the size of the waves or the strength of the currents moving the material, but the availability of material to be worked by waves and currents is also important. A vessel run aground on a bar is arguable worse off than one run aground on stationary rocks, because of the destructive capacity of the shifting action. The term bar can apply to landform features over a considerable range in size, from just a few meters in a small stream to marine depositions stretching for hundreds of kilometres along a coastline, often called barrier islands. In a nautical sense, a bar is a shoal, similar to a reef: a shallow formation of (usually) sand that is a navigation or grounding hazard. It therefore applies to a silt formation that shallows the entrance to or the course of a river or creek.

Sandbars and longshore bars

Bars that occur at or off the shoreline of a sea or a lake are related to beaches and might be considered offshore features of a beach (Bascom, 1980). At times when larger waves attack the beach berm, some of the beach material is redistributed offshore to become a longshore bar or sandbar, possibly visible at low tide. This bar forms (sometimes seaward of a trough) where the waves are breaking, because the breaking waves set up a shoreward current with a compensating counter-current along the bottom. Sand carried by the offshore moving bottom current is deposited where the current reaches the wave break (Bascom, 1980). Other longshore bars may lie further offshore, representing the break point of even larger waves, or the break point at low tide.

Bars as geological units

In addition to longshore bars discussed above that are relatively small features of a beach, the term bar can be applied to larger geological units that form off a coastline as part of the process of coastal erosion. These include spits and baymouth bars that form across the front of embayments and rias. A tombolo is a bar that forms an isthmus between an island or offshore rock and a mainland shore. The largest of the geological units of this kind are the barrier islands, such as occur along the East Coast of the United States, as well as along the Gulf coast. In places of reentrants along a coastline (such as inlets, coves, rias, and bays), sediments carried by a longshore current will fall out where the current dissipates, forming a spit. An area of water isolated behind a large bar is called a lagoon. Over time, lagoons may silt up, becoming salt marshes. See also: geomorphology, earth science.

Examples

- Abidjan, Côte d'Ivoire
- Ap Lei Chau - Ap Lei Pai, Hong Kong
- Barnegat Bay, New Jersey, United States
- Cape Canaveral, Florida, United States
- Cape St. Paul, Ghana
- Cheung Chau, Hong Kong
- Galveston Island, Texas, United States
- Great Yarmouth, England
- Lung Kwu Chau, Hong Kong
- Looe Pool, Cornwall, England
- Long Island, New York, United States
- Macao Isthmus, Macao
- Miami Beach, Florida, United States
- Minnesota Point, Duluth, Minnesota, United States
- Ninety Mile Beach, Victoria, Australia
- Ocean City, Maryland, United States
- Padre Island, Texas, United States
- Pamlico Sound, North Carolina, United States
- Port Said, Egypt
- Pui O, Hong Kong
- Sha Chau, Hong Kong
- Shek O Headland - Tai Tau Chau, Hong Kong
- Sriharikota, Andhra Pradesh, India
- Stinson Beach, California, USA
- The Coorong, South Australia, Australia
- Twin Lakes, California, United States
- Wadden islands, also known as West Frisian Islands, along the Dutch, German, and Danish coasts. The largest group of barrier islands on Earth.
- Winona, Minnesota, United States
- Yim Tin Tsai - Ma Shi Chau, Hong Kong

References

- Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p. Category:Landforms

Geography

)]] Geography is the study of the locational and spatial variation of both natural and human phenomena on Earth. The word derives from the Greek words Ge (γη) or Gaea (γεια), both meaning "Earth", and graphein (γραφειν) meaning "to describe" and "to write". Modern geography is a diverse discipline that draws influence from almost every other arena of knowledge. Geographers engage with other disciplines according to their particular research interests and, while subjects such as biology and economics have a powerful influence, there are geographers who use concepts taken from subjects such as sociology, psychology and sports science, among many others. Within the discipline there have been many long-running tensions among those seeking to define geography - whether as a 'science' or as a 'humanity', as a 'systematic' subject or 'regional' specialism and so forth - which at various times have come close to destroying geography as an academic discipline. Whilst profound differences do exist among geographers, the dual concepts of space and place provide a commonality of interest, which gives the subject a unique identity.

Structure of geography

William Hughes - who taught the geography of the Holy Lands to divinity students at King's College London - defined geography in an address in 1863: :"Mere place names are not geography. To know by heart a whole gazeteer full of them would not, in itself, constitute anyone a geographer. Geography has higher aims than this: it seeks to classify phenomena (alike of the natural and of the political world insofar as it treats of the latter) to compare, to generalise, to ascend from effects to causes and in doing so to trace out the great laws of nature and to mark their influence upon man. In a word, geography is a science, a thing not of mere names, but of argument and reason, of cause and effect." This was a specific rejection of geography as a merely descriptive discipline and also defined it as inclusive of both the physical world and the human. Within the discipline, however, there are many areas of specialism. Modern geographers tend to specialise in one of the broad branches (or sub-branches). However, most introductory geography syllabuses seek to ensure that geographers have at least working knowledge of the main focus of each branch of the subject.

Physical geography

Physical geography (or physiogeography) focuses on geography as an Earth science. It aims to understand the physical layout of the Earth, its weather and global flora and fauna patterns. Many areas of physical geography make use of geology, particularly in the study of weathering and sediment movement. Physical Geography can be divided into the following broad categories:
- Geomorphology
- Hydrology
- Glaciology
- Biogeography
- Climatology
- Pedology (soil study)
- Coastal/Marine studies
- Geodesy
- Palaeogeography
- Environmental Geography and management
- Landscape ecology Exact lines between these different areas are often difficult to draw. Sometimes Oceanography is included as a branch within physical geography, but is now considered a separate subject in its own right. Related topics: Atmosphere - Archipelago - Continent - Desert - Island - Landform - Ocean - Sea - River - Lake - Ecology - Soil - Timeline of geography, paleontology - Geostatistics - Environmental science - Oceanography - Environmental studies

Human geography

Human geography is a branch of geography that focuses on the study of patterns and processes that shape human interaction with various environments. It encompasses human, political, cultural, social, and economic aspects. While the major focus of human geography is not the physical landscape of the Earth (see Physical geography) it is hardly possible to discuss human geography without referring to the physical landscape on which human activities are being played out, and environmental geography is emerging as a link between the two. Human geography can be divided into broad categories, such as:
- Economic geography
- Development geography
- Population geography or Demography
-
- Urban geography
- Social geography
- Behavioral geography
- Cultural geography
- Political geography, including Geopolitics
-
- Historical geography
- Regional science
- Strategic geography
- Military geography
- Feminist geography
- Distinction between these fields of study have become increasingly blurred over time and the above list should not be considered definitive. Related topics: Countries of the world - Country - Nation - State - Personal union - Province - County - City - Municipality - Central place theory - Urban morphology

Socio-environmental geography

During the time of environmental determinism, geography was defined not as the study of spatial relationships, but as the study of how humans and the natural environment interact. Though environmental determinism has died out, there remains a strong tradition of geographers addressing the relationships between people and nature. There are two main subfields of socio-environmental geography:
- cultural and political ecology (CAPE) and
- risk-hazards research.

Cultural and political ecology

Cultural ecology grew out of the work of Carl Sauer in geography and a similar school of thought in anthropology. It examined how human societies adapt themselves to the natural environment. Sustainability science has been one important outgrowth of this tradition. Political ecology arose when some geographers used aspects of critical geography to look at relations of power and how they affect people's use of the environment. For example, an influential study by Michael Watts argued that famines in the Sahel are caused by the changes in the region's political and economic system as a result of colonialism and the spread of capitalism.

Risk-hazards research

Research on hazards began with the work of geographer Gilbert F. White, who sought to understand why people live in disaster-prone floodplains. Since then, the hazards field has expanded to become a multidisciplinary field examining both natural hazards (such as earthquakes) and technological hazards (such as nuclear reactor meltdowns). Geographers studying hazards are interested in both the dynamics of the hazard event and how people and societies deal with it.

Historical geography

This branch seeks to determine how cultural features of the multifarious societies across the planet evolved and came into being. Study of the landscape is one of many key foci in this field - much can be deduced about earlier societies from their impact on their local environment and surroundings. ; What's in a name? Historical geography and the Berkeley School "Historical Geography" can indeed refer to the reciprocal effects of geography and history on each other. But in the United States, it has a more specialized meaning: This is the name given by Carl Ortwin Sauer of the University of California, Berkeley to his program of reorganizing cultural geography (some say all geography) along regional lines, beginning in the first decades of the 20th Century. To Sauer, a landscape and the cultures in it could only be understood if all of its influences through history were taken into account: Physical, cultural, economic, political, environmental. Sauer stressed regional specialization as the only means of gaining expertise on regions of the world. Sauer's philosophy was the principal shaper of American geographic thought in the mid-20th century. Regional specialists remain in academic geography departments to this day. But many geographers feel that it harmed the discipline in the long run: Too much effort was spent on data collection and classification, and too little on analysis and explanation. Studies became more and more area specific as later geographers struggled to find places to make names for themselves. This probably led in turn to the 1950s crisis in Geography which nearly destroyed it as an academic discipline.

History of geography

:See main article: History of geography History of geography The Greeks are the first known culture to actively explore geography as a science and philosophy. Mapping by the Romans as they explored new lands added new techniques. During the Middle Ages, Arabs such as Idrisi, Ibn Batutta, and Ibn Khaldun maintained the Greek and Roman techniques and developed new ones. Following the journeys of Marco Polo, interest in geography spread throughout Europe. The great voyages of exploration in 16th and 17th centuries revived a desire for both accurate geographic detail, and more solid theoretical foundations. This period is also known as Great Geographical Discoveries. By the 18th century, geography had become recognized as a discrete discipline and became part of a typical university curriculum in Europe (especially Paris and Berlin). Over the past two centuries the quantity of knowledge and the number of tools has exploded. There are strong links between geography and the sciences of geology and botany, as well as economics, sociology and demographics. In the West during the 20th century, the discipline of geography went through four major phases: environmental determinism, regional geography, the quantitative revolution, and critical geography.
Geographic techniques
As spatial interrelationships are key to this synoptic science, maps are a key tool. Classical cartography has been joined by a more modern approach to geographical analysis, computer-based geographic information systems (GIS).
- Cartography studies the representation of the Earth's surface with abstract symbols (map making). Although other subdisciplines of geography rely on maps for presenting their analyses, the actual making of maps is abstract enough to be regarded separately. Cartography has grown from a collection of drafting techniques into an actual science. Cartographers must learn cognitive psychology and ergonomics to understand which symbols convey information about the Earth most effectively, and behavioral psychology to induce the readers of their maps to act on the information. They must learn geodesy and fairly advanced mathematics to understand how the shape of the Earth affects the distortion of map symbols projected onto a flat surface for viewing. It can be said, without much controversy, that cartography is the seed from which the larger field of Geography grew. Most geographers will cite a childhood fascination with maps as an early sign they would end up in the field. mathematics
- Geographic Information Systems deals with the storage of information about the Earth for automatic retrieval by a computer, in an accurate manner appropriate to the information's purpose. In addition to all of the other subdisciplines of geography, GIS specialists must understand computer science and database systems. GIS has so revolutionized the field of cartography that nearly all mapmaking is now done with the assistance of some form of GIS software.
- Geographic quantitative methods deal with numerical methods peculiar to (or at least most commonly found in) geography. In addition to spatial analyses, you are likely to find things like cluster analysis, discriminant analysis, and non-parametric statistical tests in geographic studies.
- Geographic qualitative methods, or ethnographic research techniques, are used by human geographers. In cultural geography there is a tradition of employing qualitative research techniques also used in anthropology and sociology. Participant Observation and in-depth interviews provide human geographers with qualitative data. In their study geographers use four interrelated approaches:
- Systematic - Groups geographical knowledge into categories that can be explored globally
- Regional - Examines systematic relationships between categories for a specific region or location on the planet.
- Descriptive - Simply specifies the locations of features and populations.
- Analytical - Asks why we find features and populations in a specific geographic area.
Related fields

Urban and regional planning
Urban planning and regional planning use the science of geography to assist in determining how to develop (or not develop) the land to meet particular criteria, such as safety, beauty, economic opportunities, the preservation of the built or natural heritage, etcetera. The planning of towns, cities and rural areas may be seen as applied geography although it also draws heavily upon the arts, the sciences and lessons of history. Some of the issues facing planning are considered briefly under the headings of rural exodus, urban exodus and Smart Growth.
Regional science
In the 1950s the regional science movement arose, led by Walter Isard to provide a more quantitative and analytical base to geographical questions, in contrast to the more qualitative tendencies of traditional geography programs. Regional Science comprises the body of knowledge in which the spatial dimension plays a fundamental role, such as regional economics, resource management, location theory, urban and regional planning, transport and communication, human geography, population distribution, landscape ecology, and environmental quality.
Reference

See also

- List of geography topics
- Geographical terms
- List of countries
- Geography reference tables
- Map
- Geographical renaming
- Geographic magazines
- National Geographic Society (United States)
- National Geographic Bee (United States)
- Point of Beginning
- Royal Geographical Society (United Kingdom)
External links

- [http://www.confluence.org/ Confluence.org - A work in progress, involving travelling to every point on the globe where the lines of longitude and latitude intersect and taking a photograph in each direction.]
- [http://www.aag.org/ Association of American Geographers]
- [http://www.gisuser.com/ GISuser.com, information-rich portal about GIS]
- [http://www.populationdata.net/ PopulationData.net]
- [http://www.freemaps.de/ Free Maps Germany]
- [http://www.ericdigests.org/1996-4/high.htm Using Literature To Teach Geography in High Schools. ERIC Digest.]
- [http://ericdigests.org/1992-5/geography.htm Teaching Geography at School and Home. ERIC Digest.]
- [http://ericdigests.org/1996-1/geography.htm The National Geography Content Standards. ERIC Digest.]
- [http://www.geo-guide.de Geo-Guide] extensive list of academic resources on geography and earth science
- [http://www.geopium.org Geopium: Geopolitics of Illicit Drugs in Asia]
- [http://www.nationalgeographic.com/ National Geographic Online]
- [http://www.rgs.org Royal Geographical Society]
- [http://www.rcgs.org Royal Canadian Geographical Society]
- [http://www.canadiangeographic.ca Canadian Geographic]
- [http://hypergeo.free.fr Hypergeo : Geographical Encyclopedia]
- [http://www.rare-maps.com/links.cfm Antique and Rare Maps - Art Source International] - Links to rare and antique maps and to cartography resources.
- [http://www.mapinfo.com/ MapInfo GIS Software]
- Category:School subjects als:Geografie ko:지리학 ms:Geografi ja:地理学 simple:Geography th:ภูมิศาสตร์

Shoal

Things known as shoal include:
- shoal — a sandbank or bar creating a shallow.
- shoal — a swarm of fish, also called a school
- The Shoals is the name of a region in northwest Alabama on the banks of the Tennessee River encompassing the cities of Florence, Muscle Shoals, Tuscumbia, and Sheffield.

Water

:This article focuses on water as it is experienced in everyday life. See water (molecule) for information on the chemical and physical properties of pure water (H₂O, hydrogen oxide). Water (from the Old English word wæter; c.f German "Wasser", from PIE
- wod-or, "water") is a tasteless, odorless, and nearly colorless (it has a slight hint of blue) substance in its pure form that is essential to all known forms of life and is known also as the most universal solvent. Water is an abundant substance on Earth. It exists in many places and forms. It appears mostly in the oceans and polar ice caps, but also as clouds, rain water, rivers, freshwater aquifers, and sea ice. On the planet, water is continuously moving through the cycle involving evaporation, precipitation, and runoff to the sea. Water fit for human consumption is called potable water. This natural resource is becoming more scarce in certain places as human population in those places increases, and its availability is a major social and economic concern.

Molecular properties

Forms of water

potable water] Water takes many different shapes on earth: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, aquifers in the ground, to name but a few. Through evaporation, precipitation, and runoff, water is continuously flowing from one form to another, in what is called the water cycle. Because of the importance of precipitation to agriculture, and to mankind in general, different names are given to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time. Hail, snow, fog or dew are examples. When appropriately lit, water drops in the air can refract sunlight to produce rainbows. Similarly, water runoffs have played major roles in human history as rivers and irrigation brought the water needed for agriculture. Rivers and seas offered opportunity for travel and commerce. Through erosion, runoffs played a major part in shaping the environment providing river valleys and deltas which provide rich soil and level ground for the establishment of population centers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. Because water can contain many different substances, it can taste or smell very differently. In fact, humans and other animals have developed their senses to be able to evaluate the drinkability of water: animals generally dislike the taste of salty sea water and the putrid swamps and favor the purer water of a mountain spring or aquifer.

Water in biology

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. Water carries out this role by allowing organic compounds to react in ways that ultimately allows replication. It is a good solvent and has a high surface tension, and thus allows organic compounds and living things to be transported in it. Fresh water has its greatest density at 4°C, then becoming less dense as it freezes or heats up from this point. As a stable, polar molecule prevalent in the atmosphere, it plays an important atmospheric role as an absorber of infrared radiation, crucial in the atmospheric greenhouse effect without of which, the average surface temperature would be −18° Celsius. Water also has an unusually high specific heat, which plays many roles in regulating global and regional climate, such as the Gulf Stream climate, allowing life to survive. Water is a very good solvent, chemically not unlike ammonia, and dissolves many types of substances, such as various salts and sugar, and facilitates their chemical interaction, which aids complex metabolisms. Some substances, however, do not mix well with water, including oils and other hydrophobic substances. Cell membranes, composed of lipids and proteins, take advantage of this property to carefully control interactions between their contents and external chemicals. This is facilitated somewhat by the surface tension of water. Water drops are stable due to the high surface tension of water caused by the strong intermolecular forces called cohesive forces. This can be seen when small quantities of water are put onto a nonsoluble surface such as polythene: the water stays together as drops. On extremely clean glass the water may form a thin film because the molecular forces between glass and water molecules (adhesive forces) are stronger than the cohesive forces. This property plays a key role in plant transpiration. A simple but environmentally important and unique property of water is that its common solid form, ice, floats on the liquid. This solid phase is less dense than liquid water, due to the geometry of the strong hydrogen bonds which are formed only at lower temperatures. For almost all other substances and for all other 11 uncommon phases of water ice except ice-XI, the solid form is more dense than the liquid form. Fresh water is most dense at 4°C, and will sink by convection as it cools to that temperature, and if it becomes colder it will rise instead. This reversal will cause deep water to remain warmer than shallower freezing water, so that ice in a body of water will form first at the surface and progress downward, while the majority of the water underneath will hold a constant 4°C. This effectively insulates a lake floor from the cold. While this behavior may seem obvious, even intuitive, it should be noted that almost all other chemicals are denser as solids than they are as liquids, and freeze from the bottom up. Life on earth has evolved with and adapted itself to the important features of water. The existence of abundant liquid, vapor and solid forms of water on Earth has been an important factor in the abundant colonization of Earth's various environments by life-forms adapted to those varying and often extreme conditions. Civilizations have historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, is situated between two major rivers. Large metropolises like London, Paris, New York, and Tokyo owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore and Hong Kong, have flourished for precisely this reason. In places such as North Africa and the Middle East, where water is scarcer, access to clean drinking water was and is a major factor in human development.

Astronomical position of Earth and impact on its water

Mesopotamia The coexistence of the solid, liquid, and gaseous phases of water on Earth is vital to the origin, evolution, and continued existence of life on Earth. However, if the Earth's location in the solar system were even marginally closer or further from the Sun (ie, a million miles or so), the conditions which allow the three forms to be present simultaneously would be far less likely to exist. Earth's mass allows gravity to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provides a greenhouse effect which helps maintain a relatively steady surface temperature. If Earth were less massive, a thinner atmosphere would cause temperature extremes preventing the accumulation of water except in polar ice caps (as on Mars). According to the solar nebula model of the solar system's formation, Earth's mass may be largely due to its distance from the Sun. The distance between Earth and the Sun and the combination of solar radiation received and the greenhouse effect of the atmosphere ensures that its surface is neither too cold nor too hot for liquid water. If Earth were more distant, most water would be frozen. If Earth were nearer to the Sun, its higher surface temperature would limit the formation of ice caps, or cause water to exist only as vapor. In the former case, the low albedo of oceans would cause Earth to absorb more solar energy. In the second case, a runaway greenhouse effect and inhospitable conditions similar to Venus would result. It has been proposed that life itself may maintain the conditions that have allowed its continued existence. The surface temperature of Earth has been relatively constant through geologic time despite varying solar flux, indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.

Human uses of water

Gaia hypothesis All known forms of life depend on water. Water is a vital part of many metabolic processes within the body. Significant quantities of water are used during the digestion of food. (Note however that some bacteria and plant seeds can enter a cryptobiotic state for an indefinite period when dehydrated, and come back to life when returned to a wet environment) About 72% of the fat free mass of the human body is made of water. To function properly the body requires between one and seven litres of water per day to avoid dehydration, the precise amount depending on the level of activity, temperature, humidity, and other factors. It is not clear how much water intake is needed by healthy people. However, for those who do not have kidney problems, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) dangerous to drink too little. People do often drink far more water than necessary while exercising, however, putting them at risk of water intoxication, which is frequently fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source. However, leading dieticians and nutritionists will tell you that this is the RDI (Recommended Daily Intake) of water. [http://ajpregu.physiology.org/cgi/content/full/283/5/R993]. The latest dietary reference intake report by the National Research Council recommended 2.7 liters of water total (including food sources) for women and 3.7 liters for men[http://www.iom.edu/report.asp?id=18495]. Water is lost from the body in urine and feces, through sweating, and by exhalation of water vapor in the breath. Humans require water that does not contain too much salt or other impurities. Common impurities include chemicals and/or harmful bacteria, such as crypto sporidium. Some solutes are acceptable and even desirable for perceived taste enhancement and to provide needed electrolytes.

Water as a precious resource

:See water resources for information about fresh water supplies. fresh water Because of the growth of world population and other factors, the availability of drinking water per capita is shrinking. The issue of water shortage can be solved through more production, better distribution and less waste of it. For this reason, water is a strategic resource for many countries. Many battles and wars, such as the Six-Day War in the Middle East, have been fought to gain access to it. Experts predict more trouble ahead because of the world's growing population, increasing contamination through pollution, and global warming. UNESCO's World Water Development Report (WWDR, 2003) from its World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from diseases related to the consumption of contaminated water or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds due to easily preventable water-related diseases. Some have predicted that clean water will become the "next oil", making Canada, with this resource in abundance, possibly the richest country in the world.

Regulating water distribution

Drinking water is often collected at springs or extracted from artificial borings in the ground, or wells. Building more wells in adequate places is thus a possible way to produce more water assuming the aquifers can supply an adequate flow. Other water sources are the rainwater and river or lake water. This surface water, however, must be purified for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant ocean or seawater is a more expensive solution used in coastal arid climates. The distribution of drinking water is done through municipal water systems or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource, and to finance the boring of wells or the construction of dams and reservoirs. Reducing waste, that is using drinking water only for human consumption, is another option. In some cities, such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources. Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the pollutor. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable.

The impact of water on human culture

Water is considered a purifier in most religions, including Christianity, Islam, Judaism, and Shinto. For instance, baptism in Christian churches is done with water. In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the daily Salah can only be done after ablution (Wodoo), that is, washing parts of the body in clean water. In Shinto, water is used in almost all rituals to cleanse a person or an area. Water is often believed to have spiritual powers. In Celtic mythology, Sulis is the local goddess of thermal springs; in Hinduism, the Ganga is also personified as a goddess. Alternatively, gods can be patrons of particular springs, river or lakes: for example in Greek and Roman mythology, Peneus was a river god, one of the three thousand Oceanids. The Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the ylem, or basic stuff of the universe. Water was considered cold and moist. In the theory of the four bodily humours, water was associated with phlegm. Water was also one of the Five Elements in traditional Chinese philosophy, along with earth, fire, wood, and metal. A common misconception about water is that it is a powerful conductor of electricity. Any electrical properties observable in water are due to the ions of mineral salts and carbon dioxide dissolved in it. Water does self-ionize (two water molecules become one hydroxide anion and one hydronium cation), but only at a very slight, almost immeasurable level. Pure water can also be electrolized into oxygen and hydrogen gases but without any dissolved ions, this is a very slow process and thus very little current is conducted. Many bottled water companies exploit another common misconception, advertising both purity and taste, even though pure water is tasteless.

External links

- [http://www.lsbu.ac.uk/water/phase.html Phase diagrams of water]
- [http://www.publicforuminstitute.org/issues/oceans/index.htm Oceans and Water Issues Page]
- [http://www.greenfacts.org/water-disinfectants/index.htm Scientific Facts on Water disinfectants] A faithful summary by GreenFacts of a leading scientific consensus report on Drinking Water Disinfectants published by the International Programme on Chemical Safety of the WHO.
- [http://www.hkc22.com/residentialwater.html Residential water problems and markets] Study paper from Helmut Kaiser Consultancy
- [http://www.hkc22.com/watermarketsworldwide.html Water markets worldwide] Study paper from Helmut Kaiser Consultancy
- [http://www.worldwaterforum.org/ World Water Forum]
- [http://www.unesco.org/water/wwap/ World Water Assessment Program]
- [http://unesdoc.unesco.org/images/0012/001295/129556e.pdf United Nations' World Water Development Report]
- [http://www.gemswater.org/ United Nations GEMS/Water Programme]
- [http://www.lsbu.ac.uk/water/ Water Structure and Behaviour]
- [http://www.wateraid.org/ WaterAid]
- [http://www.sahra.arizona.edu/newswatch/ SAHRA—Global Water Newswatch]
- [http://www.siwi.org/ Stockholm International Water Institute] (SIWI)
- [http://www.c-win.org/ California Water Impact Network (C-WIN)]
- [http://news.bbc.co.uk/2/hi/science/nature/3752590.stm BBC: The water debate]
- [http://www.geocities.com/tapvsbottled/ Tap Water Vs Bottled Water] - Interesting site providing facts about tap and bottled water.
- [http://www.emagazine.com/september-october_2003/0903feat1.html E the Environmental Magazine piece on bottled water] (Oct 2003).
- [http://www.iapws.org/ International Association for the Properties of Water and Steam]
- [http://ga.water.usgs.gov/edu/watercycle.html US Geological Survey: Comprehensive discussion of the water cycle, in many languages]
- [http://www.dartmouth.edu/~etrnsfer/water.htm Why is water blue?]
- [http://www.water.org.uk/home/resources-and-links/water-for-health/ask-about/adults Water requirements in adults]
- [http://www.hkc22.com/environmentaltechnology.html/ Climate change raises markets for environmental technology, drinking water and clean energies]

References

- OA Jones, JN Lester and N Voulvoulis, Pharmaceuticals: a threat to drinking water? TRENDS in Biotechnology 23(4): 163, 2005
- Category:Beverages Category:Hydrology Category:Materials Category:Natural resources Category:Nutrition zh-min-nan:Chúi als:Wasser ko:물 ja:水 ms:Air simple:Water th:น้ำ

Deposition (geology)

Deposition, also known as sedimentation, is the geological process whereby material is added to a landform. This is the process by which wind, water, or ice create a sediment deposit through the laying down of granular material that has been eroded and transported from another geographical location. Deposition occurs when the forces responsible for sediment transportation are no longer sufficient to overcome forces of particle weight and friction that resist motion. Deposition can also refer to the build up of a sediment from organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which have induced chemical processes to deposit further calcium carbonate. Category:Geological processes

Particles

In physics, a particle is an object, or body, with only a few degrees-of-freedom, including position, and perhaps orientation in space. The homogeneity and isotropy of space, being symmetries with respect to translation and rotation, may provide for particle properties such as momentum and angular momentum. These are common to classical mechanics and quantum mechanics. Certain internal degrees-of-freedom provide fixed physical properties, such as (electric) charge, or variable ones, such as spin angular momentum, most of which can only be understood within quantum mechanics.

Sea

]] A sea is a large expanse of saline water connected with an ocean, or a large, usually saline, lake that lacks a natural outlet such as the Caspian Sea and the Dead Sea. The Sea of Galilee is a small freshwater lake without a natural outlet, but the term was applied to it anyway. The term is used colloquially as synonymous with ocean, as in the tropical sea or down to the sea shore, or even sea water referring to water of the ocean. Large lakes are sometimes referred to as inland seas, such as the Great Lakes. Many of these seas can be very beautiful. Many seas are marginal seas.

List of seas, divided by ocean

Extraterrestrial seas

Lunar maria are vast basaltic plains on the Moon that were thought to be bodies of water by early astronomers, who referred to them as "seas". Liquid water is known to have existed on the surface of Mars in the distant past, and several basins on Mars have been proposed as dry sea beds. The largest is Vastitas Borealis; others include Hellas Planitia and Argyre Planitia. Liquid water is thought to be present under the surface of several moons, most notably Europa. Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than "seas". The distribution of these liquid regions will hopefully be better known after the arrival of the Cassini probe.

Science

The term "sea" has also been used in quantum physics. Dirac sea is an interpretation of the negative energy states that comprises the vacuum.

River

:For the Second World War frigate class, see River class frigate. For the state of Nigeria, see Rivers State. MyScene.]] A river is a large natural waterway. It is a specific term in the vernacular for large streams, stream being the umbrella term used in the scientific community for all flowing natural waterways. In the vernacular, stream may be used to refer to smaller streams, as may creek, run, fork, etc. Passage via a river or stream is the usual way rainfall on land finds its way to the ocean or other large body of water such as a lake. A river consists of several basic parts, originating from headwaters or a spring at the source, that flow into the main stream. Smaller side streams that join the river are tributaries. Water flow is normally confined to a channel, with a bottom or bed between banks. The lower end of a river is its base level, commonly called its mouth, a river typically widens at its end and forms what is known as a river delta or estuary.

Topography

estuary.]]A river conducts water by constantly flowing perpendicular to the elevation curve of its bed, thereby converting the positional energy of the water into kinetic energy. Where a river flows over relatively flat areas, the river will meander: start to form loops and snake through the plain by eroding the river banks. Loops that are formed are sometimes cut off, forming a shorter river channel and leaving a remnant, oxbow lake. Rivers that carry large amounts of sediment develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form estuaries. There are 4 main types of rivers. These types are:
- Youthful river - a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider.
- Mature river - a river with a gradient that is less steep than those of youthful rivers and flows more slowly than youthful rivers. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper.
- Old river - a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains.
- Rejuvenated river - a river with a gradient that is raised by the earth's movement. Where a river descends quickly over sloped topography, rapids with whitewater or even waterfalls occur. Rapids are often used for recreational purposes (see Whitewater kayaking). Waterfalls are sometimes used as sources of energy, via watermills and hydroelectric plants. Rivers begin at their source in higher ground, either rising from a spring, forming from glacial meltwater, flowing from a body of water such as a lake, or simply from damp, boggy places where the soil is waterlogged. They end at their base level where they flow into a larger body of water, the sea, a lake, or as a tributary to another (usually larger) river. In arid areas rivers sometimes end by losing water to evaporation and percolation into dry, porous material such as sand, soil, or pervious rock. The area drained by a river and its tributaries is called its watershed or catchment basin. (Watershed is also used however to mean a boundary between catchment basins.) Starting at the mouth of the river and following it upstream as it branches again and again the resulting river network forms a dendritic (tree-like) structure that is an example of a natural random fractal.

Biology

The flora and fauna of rivers are much different from those of the ocean because the water is fresh (non-salty). Living things in a river must be adapted to the current of the moving water.

Pollution

Human pollution of rivers is common, and very few rivers in the world today are clean of man-made substances. The most common pollutant is sewage piped into rivers, but chemical pollution is also common, and industrial accidents (and/or negligence) account for much of the destruction of riparian biomes. Heated water dumped into rivers by power plants and factories also affects river life.

Navigation

The Rhine is the busiest river in the world for transport ships. Inland vessels use the river to reach the major cities in Germany, Eastern France and Switzerland to transport bulk goods, liquids, containers AND passengers into the hinterland of the Port of Rotterdam and the ports of Amsterdam and Antwerp. Many millions of tons of goods are transported upstream yearly from these three sea ports to the industries near Nijmegen, Duisburg, Düsseldorf, Neuss, Köln, Koblenz, Mainz, Mannheim, Karlsruhe, Strasbourg, Colmar, Mulhouse and Basel. The lower part of the river is navigable for the largest inland vessels (up to 135 meters long and 17 meters wide) with an available depth of more than 2,50 even at the lower water levels. The further upstream, the more depth restrictions: at low water periods draught of ships is often limited to 1,90 m. for the stretch around Bingen (between the mouths of the Mosel and the Main). Upstream from Karlsruhe the Rhine is the border between France and Germany. The French have canalized the river by means of a series of hydropower dams and double ship locks, thus ensuring a year round navigable depth of 3.50 meters. (Source: NoorderSoft Waterways Database)

Dams

In places where the elevation changes of a river are great, dams for hydroelectric plants and other purposes are often built. This disrupts the natural flow of the river, and creates a lake behind the dam. Often the building of dams affects the whole of the river, even the part above the dam, as migrating fish are hindered (see fish ladder), waterflow is no longer bounded by seasonal changes and sediment flow is blocked. Dams are useful in many ways, such as providing HEP, acting as regulator of river flow so as to regulate the occurrence of flooding, which is especially important to wet-rice agriculture, and also to improve navigation and transport on the river. Often, dams such as Hoover Dam along Colorado River become famous tourist attractions. However, critics of dams, especially 'Green' advocates, argue that dams remove upper-river biodiversity such as through deforestation and forced migration of rural villages and indigenous tribes. Furthermore, trapping of river sediments behind the dams lead to salination and loss of nutrients for down-water fish. It also raises concern of eathquakes due to instablity of incompetent dams which have to support thousands of tonnes of sediments behind them. One very famous, and problematic, dam is the Aswan High Dam in the Nile.

Flooding

Flooding is a natural part of a river's cycles. Human activity, however, has upset the natural way flooding occurs by walling off rivers and straightening their courses. Removal of bogs, swamps and other wetlands in order to produce farmland has reduced the absorption zones for excess water and made floods into sudden disasters rather than gradual increases in water flow. In ancient Egypt, life was made possible through the floods of the Nile and the accompanying silt and sediment which enriched the fields with fresh nutrients. Nowadays, since people have built on these floodplains, floods are disasters, causing untold property loss each year. Human interference in the form of deforestation can also worsen conditions. The removal of vegetation leads to a reduction in Interception (vegetation stopping precipitation) and the 'weakening' of soil since plant roots no longer hold it together. As a result there is a reduced Infiltration capacity (how much water the soil can hold) and greater infiltration (precipitation going into the ground). This leads to faster soil saturation and therefore greater overland flow (also known as surface run off) and therefore, there are flash floods as the lag time decrease.

Logjams

Logjams are barriers within rivers, created by dead and uprooted trees. Over time, the obstruction prevents further logs to bypass, resulting in the creation of new network channels. According to author David R. Montgomery in his book, King of Fish, a logjam also causes water to buildup within a small space, forming peaceful pools within the main channel for young salmon to live within. The existence of these deep pools along with the complex web of channels creates an ideal salmon habitat. Today, many believe that the rebuilding of salmon runs is contingent upon reproducing the same environment shaped by logjams. As a result, many scientists have attempted to recreate artificial logjams. Marc Duboiski and Mike Ramsey of the Salmon Recovery Funding board staff, George Pess of the National Marine Fisheries Service, and Kevin Bauersfeld of Washington Department of Fish and Wildlife have prepared the Report to the Salmon Recovery Funding Board On the Engineered Log Jam (ELJ) Workshop ([http://iac.wa.gov/Documents/SRFB/Log_Jam_Report.pdf#search='log%20jams%20and%20salmon']), with the hope of mimicking natural logjams. Report to the Salmon Recovery Funding Board On the Engineered Log Jam (ELJ) Workshop."]]

Management

In its natural state a river may be inconvenient to man in a variety of ways. Rivers in inhabited areas have therefore been managed or controlled to make them more useful and less disruptive to human activity.
- The river channel may be dredged to make it deeper for navigation or to prevent flooding.
- Dams (see above) or weirs may be built to control the flow, store water, or extract energy.
- Levees may be built to prevent flooding.
- Sluice gates provide a means of controlling flow and adjusting river levels.
- floodways may be added to draw off excess river water in times of flood.
- Canals connect rivers to one another for water transfer or navigation.
- River courses may be modified to improve navigation, or straightened to increase the flow rate. River management is an ongoing activity as rivers tend to 'undo' the modifications made by man. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure.

River lists

(See also :Category:Lists of rivers.)

The world's ten longest rivers

It is difficult to measure the length of a river, mainly because rivers have a fractal property, which means that the more precise the measure, the longer the river will seem. Also, it's hard to state exactly where a river begins or ends, as very often, upstream, rivers are formed by seasonal streams, swamps, or changing lakes. This is an average measurement. # Nile (6,690 km) # Amazon (6,400 km) # Yangtze (Chang Jiang) (6,380 km) # Mississippi-Missouri (6,270 km) # Ob-Irtysh (5,570 km) # Huang He (Yellow) (5,464 km) # Amur (4,410 km) # Congo (4,380 km or 4,670 km). (The source of this river is disputed.) # Lena (4,260 km) # Mackenzie (4,240 km) For a longer list see Longest rivers. This also gives more information on measuring river lengths.

Well-known rivers (in alphabetic order)

- Aa - multiple rivers in Europe
- Amazon - largest river in the world
- American
- Amu Darya
- Amur - principal river of eastern Siberia
- Arkansas - major tributary of Mississippi River
- Arno - river through Florence
- Arvandrud (Shatt al-Arab) the large border river between Iran and Iraq.
- Brahmaputra - principal river in North East India & Tibet
- Chao Phraya - principal river of Thailand
- Colorado (Argentina)
- Colorado (U.S.) - principal river of American West
- Columbia - principal river of Pacific Northwest
- Congo - principal river of central Africa
- Danube - principal river of central and southeastern Europe
- De La Plata - the widest river in the world. South America
- Ebro - river in northwest Spain
- Elbe - major German river, Hamburg is situated on it
- Euphrates - twin principal river of Mesopotamia(Iraq)
- Ganges - principal river of India
- Han-gang - river of Seoul
- Helmand River - Principle river of (Afghanistan)
- Hari Rud (Afghanistan)
- Huang He (Yellow) - principal river of China
- Hudson - principal river of New York
- Indus - principal river of Pakistan
- Jordan - principal river of Israel
- Karun - principal (navigable) river of southern Iran.
- Kaveri - principal river of South India
- Lena - principal river of northeastern Siberia
- Mackenzie - longest river in Canada
- Magdalena - principal river of Colombia
- Main - river in Germany
- Mekong - principal river of Southeast Asia
- Mersey - river on which sits the English city of Liverpool
- Meuse - principal river of the southern provinces of the Netherlands and eastern Belgium.
- Mississippi - principal river of central United States
- Missouri - principal river of the Great Plains
- Murray - principal river of southeastern Australia
- Niger - principal river of west Africa
- Nile - Possibly the longest river in the world (or second after the Amazon)
- Ob - large river of Siberia
- Odra - major river in Eastern Europe
- Ohio - largest river between Mississippi and Appalachians
- Orinoco - principal river of Venezuela
- Parana - major South American river
- Paraguay - principal tributary of Parana river and major South American river in Brazil, Bolivia, Paraguay and Argentina
- Po - principal river of Italy
- Potomac River - principal river of the District of Columbia in the United States
- Rhine - principal river of northwestern Europe
- Rhône - principal river of southern France
- Rio Grande - border between United States and Mexico
- Saint Lawrence - drains Great Lakes
- Seine - river of Paris
- Segura- in southeast Spain
- Severn- longest river in Great Britain
- Shinano-gawa - longest river in Japan
- Snake - largest tributary to the Columbia river in Washington
- Tajo - largest river in the Iberian Peninsula
- Tay - largest river in Scotland
- Thames - river of London
- Tiber - river of Rome
- Tigris - twin principal river of Mesopotamia(Iraq)
- Tonegawa - largest river in Japan
- Vistula - principal river of Poland
- Volga - principal river of Russia
- Yangtze (Chang Jiang) - longest river in China
- Yenisei - large river of Siberia
- Yukon - principal river of Alaska and Yukon Territory
- Zambezi - principal river of southeastern Africa

Other lists

- List of waterways
- List of rivers by continent
- List of rivers of Europe
- Rivers of the United Kingdom
- List of rivers of Asia
- List of rivers of Africa
- List of rivers of Australia
- List of rivers of New Zealand
- List of rivers of the Americas
- List of rivers of Oceania
- List of river name etymologies

Rivers in myth and fiction

Real rivers

- The Thames in Edward Rutherfurd's London.
- The Thames in Jerome K. Jerome's Three Men in a Boat.
- The Thames and the Congo in Joseph Conrad's Heart of Darkness.
- The Mississippi in Mark Twain's Huckleberry Finn.
- The River Liffey through Dublin in James Joyce's Finnegans Wake.

Mythological rivers

- In Greek mythology, the Acheron, Cocytus, Phlegethon, Lethe and Styx (the five rivers of Hades); and the Eridanus.
- The Alph, an underground river imagined by various mystics and mentioned in Coleridge's poem Kubla Khan.
- The Sambation river stops flowing every Saturday.

Fictional rivers

- River Ankh traversing the city of Ankh-Morpork in Terry Pratchett's Discworld series.
- Chocolate river in Willy Wonka and the Chocolate Factory.
- River Djel in the country of Djelibeybi in Terry Pratchett's Discworld series.
- The River in the Riverworld novels of Philip José Farmer.
- Rivers of Middle-earth in various works of J. R. R. Tolkien.

External links

- [http://www.srbc.net/about.htm Management: River Basin Commissions]. Category:Bodies of water Category:Geomorphology zh-min-nan:Hô ja:川 ko:강 ms:Sungai simple:River th:แม่น้ำ

Sand

Sand is an example of a class of materials called granular matter. Sand is a naturally occurring, finely divided rock, comprising particles or granules ranging in size from ¹⁄₁₆ to 2 millimeters. An individual particle in this range size is termed a sand grain. The next smaller size class in geology is silt: particles below ¹⁄₁₆ mm down to ¹⁄₂₅₆ mm (0.004 mm) in size. The next larger size class above sand is gravel, with particles ranging up to 64 mm (see grain size for standards in use). The most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide), usually in the form of quartz which because of its chemical inertness and considerable hardness is quite resistant to weathering. However, the composition of sand varies according to local rock sources and conditions. The bright white sands found in tropical and subtropical coastal settings are ground-up limestone. Arkose is a sand or sandstone with considerable feldspar content which is derived from the weathering and erosion of a usually nearby granite. Some locations have sands that contain magnetite, chlorite, glauconite, or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts. The chlorite-glauconite bearing sands are typically green in color, as are sands derived from basalts (lavas) with a high olivine content. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, white color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones. Sand is transported by wind or water and deposited in the form of beaches, dunes, sand spits, sand bars, and the like. In most deserts, sand is a dominant constituent of the soil. The study of sand is called arenology.

Uses of sand

arenology Sand is often a principal component of the aggregate used in the preparation of concrete. Sand manufactured at rock crusher plants for use as an aggregate is called mansand. Graded sand is used as an abrasive in sandblasting and is also used in media filters for filtering water. Brick manufacturing plants use Sand as an additive with a mixture of clay and other materials for manufacturing bricks. Sandy soils are ideal for certain crops such as watermelons and peanuts and are often preferred for intensive dairy farming because of their excellent drainage characteristics. Sandbags are used for protection against floods and gun fire. They can be easily transported when empty, and filled with local sand. People, especially children, love to play with sand on a beach or in a sandpit. See sand art and play for details.

Hazards of sand

Bags of sand now typically carry labels warning the user to wear respiratory protection and avoid breathing the fine silica dust. There have been a number of lawsuits in recent years where workers have sought damages after they developed silicosis, a lung disease caused by inhalation of fine silica particles. People have been severely injured and even killed after digging sand "caves" in large dunes, sandhills, or even on beaches when the cave or tunnel collapsed upon them.

Silt

Silt refers to soil or rock particles of a certain very small size range (see grain size). On the Wentworth scale, silt particles fall between ¹⁄₂₅₆ and ¹⁄₁₆ mm (3.9 to 62.5 μm), larger than clay but smaller than a sand. In actuality, silt is chemically distinct from clay, and their size ranges overlap. According to the USDA Unified Soil Classification System (USCS) and the AASHTO Soil Classification system, the sand-silt distinction is made at the 0.075 mm particle size (i.e. material passing the #200 sieve), and silts and clays are distinguished by their plasticity. Silt is produced by the mechanical

Barrier island

Sandbars and longshore bars

Bars as geological units

Examples

References

Geography

Structure of geography

Physical geography

Human geography

Socio-environmental geography

Cultural and political ecology

Risk-hazards research

Historical geography

History of geography

Geographic techniques

Related fields

Urban and regional planning

Regional science

Reference

See also

External links

Shoal

Water

Molecular properties

Forms of water

Water in biology

Astronomical position of Earth and impact on its water

Human uses of water

Water as a precious resource

Regulating water distribution

The impact of water on human culture

See also

External links

References

Deposition (geology)

Particles

See also

Sea

List of seas, divided by ocean

Pacific Ocean

Atlantic Ocean

Indian Ocean

Arctic Ocean

Southern Ocean

Landlocked seas

Extraterrestrial seas

Science

See also

River

Topography

Biology

Pollution

Navigation

Dams

Flooding

Logjams

Management

River lists

The world's ten longest rivers

Well-known rivers (in alphabetic order)

Other lists

Rivers in myth and fiction

Real rivers

Mythological rivers

Fictional rivers

See also

Crossings

Transport

External links

Sand

Uses of sand

Hazards of sand

See also

Silt