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Coast

Coast

.]] The coast is defined as the part of the land adjoining or near the ocean. A coastline is properly, a line on a map indicating the disposition of a coast but the word is often used to refer to the coast itself. The adjective, coastal describes something as being on, near or having to do with a coast. Coast is a very specific term and is only applied to that part of an island or continent that borders an ocean or its saltwater tributaries. A pelagic coast refers to a coast which fronts the open ocean, as opposed to a more sheltered coast in a gulf or bay. A shore on the other hand, can refer to parts of the land which adjoin any large body of water, including oceans (sea shore) and lakes (lake shore). Similarly, the somewhat related term bank refers to the land alongside or sloping down to a river (river bank) or of a body of water smaller than a lake. Bank is also used in some parts of the world to refer to an artificial ridge of earth intended to retain the water of a river or pond. In other places this may be called a levee. While many scientific experts might agree on a common definition of the term "coast", the delineation of the inland extents of a coast differ according to jurisdiction, with many scientific and government authorities in various countries differing for economic and social policy reasons. This is usually because defining lands as part of a coast may be seen to have environmental implications which would prevent development or attach regulations to their use.

Environmental importance

The coast and its adjacent areas on and off shore is an important part of a local ecosystem as the mixture of fresh water and salt water in estuaries provides many nutrients for marine life. Salt marshes and beaches also support a diversity of plants, animals, and insects crucial to the food chain. Like the ocean which shapes them, coasts are a dynamic environment with constant change. The earth's natural processes, particularly sea level rise, waves and various weather phenomena, have resulted in the erosion accretion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys (rias).

Human impacts

Coasts also face many environmental challenges relating to human-induced impacts. The human influence on climate change is thought to be a contributing factor of an accelerated trend in sea level rise which threatens coastal habitat as natural systems struggle to adapt faster. Human development of coastal land, particularly for recreational or industrial uses are similarly threatened by sea level rise, but also contribute to aesthetic problems of land use and reduced natural coastal habitat. Pollution is an ongoing concern along coasts with garbage and industrial debris littering beaches and sometimes entire coasts. The transportation of petroleum in tankers is a major hazard both for the open ocean and along coasts, particularly when large oil spills occur. Another major hazard for coastal marine life is the large number of small oil spills created by large and small vessels powered by petroleum which flush bilge water directly into the ocean. Both the terms coast and coastal are often used to describe a geographic location or region. For example, New Zealand's West Coast, or the East and West Coasts of the United States. A large part of the global population inhabits areas near a coast, partly to take advantage of marine resources such as fish, but more importantly to participate in seaborne trade with other nations. Many of the world's major cities that have developed in recent centuries were built on or near good harbours and have large port facilities to take advantage of marine transportation. Jurisdictions which are landlocked and have no coast are often at an economic disadvantage with overseas trade being more difficult; sometimes being forced to go to extravagant measures such as building canals to permit ocean-going vessels to travel inland. Coasts, especially those with beaches and warm water are also an important draw for tourists. In many island nations such as those of the Mediterranean, South Pacific and Caribbean, tourism by those who come to enjoy the coast is central to the economy. Coasts are popular destinations because of recreational activities such as swimming, fishing, surfing, boating, and sun bathing. Many tourists and residents also enjoy the salt air by the sea coast which some consider to have health benefits. Coastal weather is heavily influenced by the ocean and while this can sometimes result in dangerous storms such as Nor'easters and hurricanes, the coastal climate is often cooler and more temperate than corresponding inland areas. Consequently tourists from areas experiencing extremely warm and humid weather seek coastal areas for these reasons. The coast, especially for isolated nations such as Japan, the United Kingdom, Australia, New Zealand, Canada or the United States is often a crucial defensive frontier, both for warding off military invaders but also smugglers and illegal migrants. Coastal defenses have thus long been erected in many nations. Most coastal countries also have a navy and some form of coast guard.

Types of coast

- emergent coastline - coast has risen or sea level has fallen from previous level.
- submergent coastline - coast has fallen or sea level has risen from previous level.
- concordant coastline - rock bands run parallel to shore.
- discordant coastline - rock bands run perpendicular to shore.

Origins

The Oceans of the world most likely originated by comets striking the Earth.

Exploration

salinity Travel on the surface of the ocean through the use of boats dates back to prehistoric times, but only in modern times has extensive underwater travel become possible. The deepest point in the ocean is the Mariana Trench located in the Pacific Ocean near the Northern Mariana Islands. It has a maximum depth of 10,923 m (35,838 ft) [http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html]. It was fully surveyed in 1951 by the British naval vessel, "Challenger II" which gave its name to the deepest part of the trench, the "Challenger Deep". Much of the bottom of the world's oceans is unexplored and unmapped. A global image of many underwater features larger than 10 km was created in 1995 based on gravitational distortions of the nearby sea surface.

Climate

One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where the system forms). Ocean currents greatly affect Earth's climate by transferring warm or cold air and precipitation to coastal regions, where they may be carried inland by winds. The Antarctic Circumpolar Current encircles that continent, influencing the area's climate and connecting currents in several oceans.

Ecology

The oceans are home to the majority of plant and animal life on Earth. These lifeforms include:
- fish
- cetacea such as whales, dolphins and porpoises,
- cephalopods such as the octopus
- crustaceans such as lobsters and shrimp
- marine worms
- plankton
- krill

Economy

The oceans are essential to transportation: a huge portion of the world's goods are moved by ship between the world's seaports. Important ship canals include the Saint Lawrence Seaway, Panama Canal, and Suez Canal.

Ancient oceans

Continental drift has reconfigured the Earth's oceans, joining and splitting ancient oceans to form the current oceans. Ancient oceans include:
- Panthalassa, the vast world ocean that surrounded the Pangaea supercontinent.
- Tethys Ocean, the ocean between the ancient continents of Gondwana and Laurasia.
- Iapetus Ocean, the southern hemisphere ocean between Baltica and Avalonia.

Ocean rowing

Extraterrestrial oceans

Earth is the only known planet with liquid water on its surface, and is certainly the only such in our own solar system. However, liquid water is thought to be present under the surface of several natural satellites, particularly the Galilean moons of Europa, and, with less certainty, its fellows Callisto and Ganymede. Other icy moons may have once had internal oceans that have now frozen, such as Triton. The planets Uranus and Neptune may also possess large oceans of liquid water under their thick atmospheres, though their internal structure is not well understood at this time. There is currently much debate over whether Mars once had an ocean of water in its northern hemisphere, and over what happened to it if it did; recent findings by the Mars Exploration Rover mission indicate it had some long-term standing water in at least one location, but its extent is not known. 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 an "ocean". The distribution of these liquid regions will hopefully be better known after the full analysis of data from the Huygens probe of the Cassini-Huygens space mission, which dropped onto Titan's surface in January 2005. Titan is also thought likely to have a subterranean water ocean under the mix of ice and hydrocarbons that forms its outer crust.

Oceans in film

- In the movie Muppet Treasure Island, a non-specific ocean is featured, and referred to as the "Big Blue Wet Thing". Oceans have also been featured in many other movies such as Free Willy. To list more, click edit beside "Oceans on Film"

External links

- [http://www.oceanexplorer.noaa.gov/ Ocean Explorer] - An educational and reference resource from NOAA
- [http://news.bbc.co.uk/2/hi/science/nature/4033555.stm Science taps into ocean secrets]
- [http://www.palomar.edu/oceanography/salty_ocean.htm Why is the ocean salty?]
- [http://ioc.unesco.org/oceanteacher/resourcekit/M3/Formats/Geography/OceansSeas.htm Official IHO boundaries of Oceans and Seas]
- [http://www.thehydrogenexpedition.com The Hydrogen Expedition] The first circumnavigation of the globe in a hydrogen fuel cell powered boat
- [http://www.coreocean.org Coreocean]
- [http://www.nopp.org/ NOPP - The National Oceanographic Partnership Program] Category:Bodies of water Category:Oceanography zh-min-nan:Hái-iûⁿ ko:대양 ms:Lautan ja:大洋 simple:Ocean th:มหาสมุทร

Headlands and bays

]] A headland is an area of land adjacent to water on three sides. A bay is the reverse, an area of water bordering land on three sides. Large headlands may also be called peninsulas, long, narrow and high headlands promontories. When headlands dramatically affect the ocean currents they are often called capes. A gulf generally occupies an area larger than a bay and may itself contain one or more bays.

Geology and geography

Headlands and bays are usually found together on the same stretch of coastline. Headlands and bays form on discordant coastlines, where bands of rock of alternating resistance run perpendicular to the coast. Bays form where weak (less resistant) rocks (such as sands and clays) are eroded, leaving bands of stronger (more resistant) rocks (such as chalk, limestone, granite) forming a headland, or peninsula. Wave refraction occurs on headlands concentrating wave energy on them, so many other landforms, such as caves, natural archs and stacks, form on headlands. Wave refraction disperses wave energy through the bay, and along with the sheltering effect of the headlands this protects bays from storms. This effect means that the waves reaching the shore in a bay are usually constructive waves, and because of this most bays feature a beach. A bay may be only metres across, or it could be hundreds of kilometres across. Sometimes bays form where movements of the earth's crust (tectonics) bring areas of land together, or move them apart. Usually these bays are referred to as seas or gulfs and not bays. "Capes and bays geography" is a derogatory term for the approach to teaching geography that requires students to learn by rote the names of large number of geographical features rather than taking a more theoretically driven approach.

List of some well-known headlands

- Africa
- Cape Agulhas in South Africa
- Cape of Good Hope in South Africa
- Cape Juby in Morocco
- Europe
- Cabo da Roca in Portugal
- Cape Arkona in Germany
- Cape Finisterre in Spain
- North Cape in Norway
- Cape Wrath in Scotland
- Asia
- Kanyakumari or Cape Comorin in Tamil Nadu, India
- Cape Engaño on the Philippines
- Indira Point in Andaman and Nicobar Islands, India
- Cape Dezhnev in Russia
- North American, Central America and the Caribbean
- Cape Canaveral in Florida, USA
- Cape Chidley in Newfoundland and Labrador/Nunavut, Canada
- Cape Cod in Massachusetts, USA
- Cape Hatteras in North Carolina, USA
- Cape Henry in Virginia, USA
- Cape Prince of Wales in Alaska, USA
- Cape Girardeau in Missouri, USA "The only inland cape in the world."
- South America
- Cape Froward in Chile
- Cape Horn in Chile
- Cape Virgenes in Argentina
- Oceania
- Cape Egmont in New Zealand
- Cape Foulwind in New Zealand
- Cape Leeuwin in Australia
- Cape Reinga in New Zealand
- Cape York in Australia
- East Cape in New Zealand
- North Cape in New Zealand
- South East Cape in Australia
- Young Nick's Head in New Zealand

List of some well-known bays

- Africa
- Gulf of Guinea
- Gulf of Sidra - coast of Tunisia and Libya
- Europe - Atlantic
- Bay of Biscay in France and Spain
- Lyme Bay off the southern coast of England
- Europe - Baltic Sea
- Gulf of Bothnia between Sweden and Finland
- Gulf of Finland between Finland and Estonia
- Bay of Gdansk between Poland and Kaliningrad Oblast
- Bay of Puck
- Vistula Bay
- Bay of Pomerania, between Poland and Germany
- Bay of Szczecin, between Poland and Germany
- Bay of Greifswald in Germany
- Bay of Mecklenburg, between Germany and Denmark
- Bay of Lubeck, in Germany
- Bay of Kiel, between Germany and Denmark
- Riddarfjärden in Stockholm, Sweden
- Europe - Mediterranean Sea
- Adriatic Sea's Boka Kotorska in Montenegro
- Asia
- Bay of Bengal, near Bengal (India/Bangladesh)
- Bohai Gulf (China)
- Bohai Bay
- Laizhou Bay
- Liaodong Bay
- Gulf of Cambay(Khambhat), Gujarat (India)
- Gulf of Kutch, Gujarat (India)
- Manila Bay on Luzon island in the Philippines
- Persian Gulf between Saudi Arabia, Kuwait, Iraq, and Iran
- Red Sea
- Subic Bay on Luzon island in the Philippines, the site of a former US Navy base
- North American, Central America and the Caribbean
- Baffin Bay, between Canada and Greenland
- Bahía de Banderas, Mexico
- Bay of Green Bay in Wisconsin
- Bay of Pigs on Cuba
- Buzzards Bay in Massachusetts
- Cape Cod Bay in Massachusetts
- Chesapeake Bay mostly in Maryland
- Delaware Bay between Delaware and the New Jersey
- Galveston Bay in Texas
- Georgian Bay on Lake Huron
- Grand Traverse Bay in Michigan
- Gulf of California between the Baja California peninsula and the Mexican mainland.
- Gulf of Santa Catalina in California
- Gulf of Maine in Maine
- Gulf of Mexico between Mexico and the United States
- Hudson Bay, between the Canadian provinces and territories of Manitoba, Ontario, Quebec and Nunavut
- James Bay, between Ontario and Quebec, opens to Hudson Bay to the north
- Massachusetts Bay in Massachusetts
- Mobile Bay in Alabama
- Monterey Bay in California
- Narragansett Bay in Rhode Island
- Penobscot Bay in Maine
- Saginaw Bay in Michigan
- San Francisco Bay in California
- Tampa Bay in Florida
- South America
- Oceania
- Great Australian Bight off the south coast of Australia
- Botany Bay, near Sydney, Australia
- Gulf of Carpentaria, Australia
- Bay of Islands, New Zealand
- Bay of Plenty, New Zealand
- Hauraki Gulf, New Zealand
- Hawke Bay, New Zealand
- North Taranaki Bight, New Zealand
- Port Phillip Bay, Australia
- South Taranaki Bight, New Zealand
- Tasman Bay, New Zealand A couple of non-gulfs (actually straits) are:
- Gulf of Oman
- Gulf of Aden

External links

- [http://www.georesources.co.uk/leld.htm GeoResources - diagrams of headland and bay formation] Category:Bodies of water ko:만 ja:湾

Shore

:For the construction term, see shoring shoring A shore (also shoreline), is the land at the edge of a large body of water, such as an ocean, sea, or large lake. Shores are influenced by the topography of the surrounding landscape, as well as by the weather-induced erosion, such as waves. The geological composition of soils dictates the type of shore which is created. Although a beach is a synonym for a shore, the term typically refers to shores which are sandy or pebbly, which can be produced by erosion of sedimentary soils. Category: Landforms

Stream bed

A stream bed is the channel bottom of a stream or river or creek; the physical confine of the normal water flow. The lateral confines (channel margins) during all but flood stage are known as the stream banks or river banks. In fact, a flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is that part of the channel just at the "normal" water line, and the banks are that part above the water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages, and therefore might support vegetation some or much of the time. The descriptive terms right bank and left bank always apply from the perspective of looking downstream (in the direction the current is going). The nature of any stream bed is always a function of the flow dynamics and the local geologic materials influenced by that flow. With small streams in mesophytic regions, the nature of the stream bed is strongly responsive to conditions of precipitation runoff. Where natural conditions of either grassland or forest ameliorate peak flows, streambeds are stable, possibly rich with organic matter, and exhibit minimal scour. These streams support a rich biota. Where conditions produce unnatural levels of runoff, such as occurs below roads, the streambeds will exhibit a greater amount of scour, often down to bedrock, and banks may be undercut. This process greatly increases watershed erosion and results in thinner soils upslope from the stream bed as the channel adjusts to the increase in flow.

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

Levee

:This article is about the type of dam. See also Levee (event) A levee, levée (from the feminine past participle of the French verb lever, "to raise"), floodbank or stopbank is a natural or artificial embankment or dike, usually earthen, which parallels the course of a river. The word levee seems to have come into English through its use in colonial Louisiana.

Artificial levees

Louisiana.]] The main purpose of artificial levees is to prevent flooding of the adjoining countryside; however, they also confine the flow of the river resulting in higher and faster water flow. Levees are usually built by piling earth on a cleared, level surface. Broad at the base, they taper to a level top, where temporarily embankments or sandbags can be placed. Because flood discharge intensity increases in levees on both river banks, and because silt deposits raise the level of riverbeds, planning and auxiliary measures are vital. Sections are often set back from the river to form a wider channel, and flood valley basins are divided by multiple levees to prevent a single breach from flooding a large area. Artificial levees require substantial engineering. Their surface must be protected from erosion, so they are planted with vegetation such as Bermuda grass in order to bind the earth together. On the land side of high levees, a low terrace of earth known as a banquette is usually added as another anti-erosion measure. On the river side, erosion from strong waves or currents presents an even greater threat to the integrity of the levee. The effects of erosion are countered by planting with willows, weighted matting or concrete revetments. Separate ditches or drainage tiles are constructed to ensure that the foundation does not become waterlogged. The first levees were constructed over 3,000 years ago in ancient Egypt, where a system of levees was built along the left bank of the River Nile for more than 600 miles (966 km), stretching from modern Aswan to the Nile Delta on the shores of the Mediterranean. The Mesopotamian civilizations and ancient China also built large levee systems. Because a levee is only as strong as its weakest point, the height and standards of construction have to be consistent along its length. This requires a strong governing authority to guide the work, and may have been a catalyst for the development of systems of governance in early civilizations. In modern times, prominent levee systems exist along the Mississippi River and Sacramento Rivers in the United States, and the Po, Rhine, Loire, Vistula, and Danube in Europe. The Mississippi levees represent one of the largest such systems found anywhere in the world. They comprise over 3,500 miles (5,600 km) of levees extending some 1,000 miles (1,600 km) along the Mississippi, stretching from Cape Girardeau, Missouri to the Mississippi Delta. They were begun by French settlers in Louisiana in the 18th century to protect the city of New Orleans. The first Louisianian levees were about 3 feet (0.9 m) high and covered a distance of about 50 miles (80 km) along the riverside. By the mid-1980s, they had reached their present extent and averaged 24 feet (7 m) in height; some Mississippi levees are as much as 50 feet (15 m) high. The Mississippi levees also include some of the longest continuous individual levees in the world. One such levee extends southwards from Pine Bluff, Arkansas for a distance of some 380 miles (611 km).

Natural levees

The ability of a river to carry sediment varies very strongly with its speed. When a river floods over its banks, the water spreads out, slows down, and deposits its load of sediment. Over time, the river's banks are built up above the level of the rest of the floodplain. The resulting ridges are called natural levees. When the river is not in flood state it may deposit material within its channel, raising its level. The combination can raise not just the surface, but even the bottom of the river above the surounding country. Natural levees are especially noted on the Yellow River in China near the sea where oceangoing ships appear to sail high above the plain on the elevated river. Natural levees are a common feature of all meandering rivers in the world.

Levees in tidal waters

The same basic process occurs in tidal creeks when the incoming tide carries mineral material of all grades up to the limit imposed by the energy of the flow. As the tide overflows the sides of the creek towards high water, the flow rate at the brink slows and larger sediment is deposited, forming the levee. At the height of the tide, the water stands on the salt-marsh or flats and the finer particles slowly settle, forming clay. In the early ebb, the water level in the creek falls leaving the broad expanse of water standing on the marsh at a higher level. The area of water on the marsh is much greater than the water surface of the creek so that in the latter, the flow rate is much greater. It is this rush of water, perhaps an hour after high water, which keeps the creek channel open. The cross-sectional area of the water body in the creek is small compared with that initially over the levee which at this stage is acting as a weir. The deposited sediment (coarse on the levee and on the mud flats or salt-marsh) therefore tends to stay put so that, tide by tide, the marsh and levee grow higher until they are of such a height that few tides overflow them. In an active system, the levee is always higher than the marsh. That is how it came to be called "une rive levée" or raised shore.

Levee breaches

The Great Mississippi Flood occurred in 1927 when the Mississippi River breached levees and flooded 27,000 square miles, killing 246 people in seven states and displacing 700,000 people. In the North Sea flood of 1953, levees and flood defenses collapsed in the United Kingdom and the Netherlands, killing over 2,100 people. During the passage of Hurricane Katrina in August 2005, floodwaters breached levees protecting New Orleans, causing catastrophic flooding and resulting in the total evacuation of the city (effects on levees are discussed further in Effect of Hurricane Katrina on New Orleans).

Levees in popular culture

The song "I've Been Working on the Railroad" was, according to Carl Sandburg, originally "I've Been Working on the Levee" before the days of railroads. The song "When the Levee Breaks" written and first recorded by Memphis Minnie and Kansas Joe McCoy in 1929, and later covered by Led Zeppelin and others, was about the Great Mississippi Flood. Don McLean mentions driving his "Chevy to the levee" in his song "American Pie". Canadian band The Tragically Hip penned "New Orleans is Sinking" in 1989.

External link

- [http://www.pbs.org/now/science/neworleans.html New Orleans and the Delta]
- ja:堤防

Ecosystem

In ecology, the word ecosystem is an abbreviation of the term, ecological system. Some consider this the basic unit in ecology. Ecosystems are not to be confused with biomes because they are smaller than biomes. They can be as big as the sahara desert, but as small as a pond. In general terms an ecological system can be thought of as an assemblage of organisms (plant, animal and other living organisms—also referred to as a biotic community or biocoenosis) living together with their environment (or biotope), functioning as a loose unit. That is, a dynamic and complex whole, interacting as an "ecological unit". Early conceptions of this unit were as a structured functional unit in equilibrium. This equilibrium was characterized by energy and matter flows between its constituent elements. Others considered this vision limited, and preferred to understand an ecosystem in terms of cybernetics. From this view an ecological system is not a structured functional unit in equilibrium, but a functional organisation at dynamic equilibrium, or what was also called steady state. This branch of ecology that gave rise to this view has become known as Systems Ecology. Steady state is understood as the phase of an ecological systems evolution when the organisms are "balanced" with each other and their environment. This balance is achieved through various types of symbiosis, such as predation, parasitism, mutualism, commensalism, competition, and amensalism. Introduction of new elements, whether abiotic or biotic, into an ecosystem tend to have a disruptive effect. In some cases, this can lead to ecological collapse and the death of many native species. The abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem. That is, how far the ecosystem is away from steady state. The size and scale of an ecosystem can vary widely. It may be a whole forest, as well as a small pond, or even the geobiosphere itself. Different ecosystems are often separated by geographical barriers, like deserts, mountains or oceans, or are isolated otherwise, like lakes or rivers. As these borders are never rigid, ecosystems tend to blend into each other. As a result, the whole earth can be seen as a single ecosystem, or a lake can be divided into several ecosystems, depending on the scale used.

History

The term ecosystem first appeared in a 1935 publication by the British ecologist Arthur Tansley (Tansley, 1935). However, the term had been coined already in 1930 by Tansley's colleague Roy Clapham, who was asked if he could think of a suitable word to denote the physical and biological components of an environment considered in relation to each other as a unit. Tansley expanded on the term in his later work, adding the ecotope concept to define the spatial context of ecosystems (Tansley, 1939). Modern usage of the term derives from the work of Raymond Lindeman in his classic study of a Minnesota lake (Lindeman, 1942). Lindeman's central concepts were that of functional organisation and ecological energy efficiency ratios. This approach is connected to ecological energetics and might also be thought of as environmental rationalism. It was subsequently applied by H.T.Odum, sometimes called the 'father' of ecosystems ecology, in founding the transdiscipline known as Systems Ecology. Category:Ecology Category:Symbiosis

External link

- [http://www.ericdigests.org/2004-1/ecosystems.htm Teaching about Ecosystems]
- [http://www.millenniumassessment.org/en/index.aspx Millennium Ecosystem Assessment] (2005)
- [http://www.greenfacts.org/ecosystems/index.htm A popularized version of the Millennium Ecosystem Assessment] by GreenFacts.

References

- Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology. Ecology 23: 399-418.
- Tansley, A. G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16: 284-307.
- Tansley, A.G. 1939. The British Islands and their Vegetation. Volume 1 of 2. University Press, Cambridge, Cambridge, United Kingdom. 484 pg. Category:Ecology ko:생태계 ja:生態系

Salt

: This article is about the general chemical term salt. For the everyday meaning, see edible salt or its main ingredient, sodium chloride. For other meanings of the word salt, see salt (disambiguation). In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. These ions can be inorganic (Cl^-) as well as organic (CH₃-COO^-) and monoatomic (F^-) as well as polyatomic ions (SO₄^2-). Solutions of salts in water are called electrolytes. Electrolytes as well as molten salts conduct electricity. Zwitterions are salts that contain an anionic center and a cationic center in the same molecule, examples are the amino acids, many metabolites, peptides, and proteins. Mixtures of many different ions in solution like in the cytoplasm of cells, in blood, urine, plant saps, and mineral waters usually do not form defined salts after evaporation of the water. Therefore their salt content is given for the respective ions. Impure salt is a name for salt which has lost its saltiness. It can also refer to natron.

Appearance

Consistency

Salts are usually solid crystals with a relatively high melting point. However, there exist salts that are liquid at room temperature, so-called ionic liquids. Inorganic salts usually have a low hardness and a low compressibility, similar to edible salt.

Color

Salts can be clear and transparent (sodium chloride), opaque (titanium dioxide), and even metallic and lustrous (iron disulfide). Salts exist in all different colors, e.g. yellow (sodium chromate), orange (sodium dichromate), red (mercury sulfide), mauve (cobalt dichloride hexahydrate), blue (copper sulfate pentahydrate, ferric hexacyanoferrate), green (nickel oxide), colorless (magnesium sulfate), white (titanium dioxide), and black (manganese dioxide). Most minerals and inorganic pigments as well as many synthetic organic dyes are salts.

Taste

Different salts can elicit all five basic tastes, i.e. salty (sodium chloride), sweet (lead diacetate), sour (potassium bitartrate), bitter (magnesium sulfate), and umami or savory (monosodium glutamate).

Odor

Pure salts are odorless, while impure salts may smell after the acid (e.g. acetates like acetic acid (vinegar), cyanides like hydrogen cyanide (almonds)) or the base (e.g. ammonium salts like ammonia).

Nomenclature

The name of a salt starts with the name of the cation (e.g. sodium or ammonium) followed by the name of the anion (e.g. chloride or acetate). Salts are often referred to only by the name of the cation (e.g. sodium salt or ammonium salt) or by the name of the anion (e.g. chloride or acetate). Common salt-forming cations are:
- ammonium NH₄⁺
- calcium Ca²⁺
- iron Fe²⁺ and Fe³⁺
- magnesium Mg²⁺
- potassium K⁺
- pyridinium C₅H₅NH⁺
- quaternary ammonium NR₄⁺
- sodium Na⁺ Common salt-forming anions (and the name of the parent acids in parentheses) are:
- acetate CH₃-COO^- (acetic acid)
- carbonate CO₃^2- (carbonic acid)
- chloride Cl^- (hydrochloric acid)
- citrate HO-C(COO^-)(CH₂-COO^-)₂ (citric acid)
- cyanide C≡N^- (hydrogen cyanide)
- hydroxide OH^- (water)
- nitrate NO₃^- (nitric acid)
- nitrite NO₂^- (nitrous acid)
- oxide O^2- (water)
- phosphate PO₄^3- (phosphoric acid)
- sulfate SO₄^2- (sulfuric acid)

Formation

Salts are formed by a chemical reaction between:
- a base and an acid, e.g. NH₃ + HCl → NH_{4_Cl}
- a metal and an acid, e.g. Mg + H₂SO₄ → MgSO₄ + H₂ Salts can also form if solutions of different salts are mixed, their ions recombine, and the new salt is insoluble and precipitates (see: Solubility equilibrium).

References

- Kurlansky, Mark (2002). Salt: A World History. Walker Publishing Company. ISBN: 0142001619
- silting is the natural deposit of salt from sea water

Marsh

: This article is about marsh, a type of wetland. For other uses of the word marsh see marsh (disambiguation). marsh (disambiguation) In geography, a marsh is a type of wetland, featuring grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water. A marsh is different from a swamp, which is dominated by trees rather than grasses and low herbs. The water of a marsh can be fresh, brackish, or saline. Coastal marshes may be associated with estuaries and along waterways between coastal barrier islands and the inner coast. Marshes are critically important wildlife habitat, often serving as breeding grounds for a wide variety of animal life. Constructed wetlands featuring surface-flow design are usually in the form of a marsh.

Beach

A beach or strand is a geological formation consisting of loose rock particles such as sand, shingle, cobble, or even shell along the shoreline of a body of water.

Components

Some geologists consider a beach to be just this shoreline feature of deposited material, but William Bascom (1980) has argued that a beach is the entire system of sand set in motion by waves to a depth of ten meters (30+ feet) or more off ocean coasts. Submerged, longshore bars are therefore also part of the beach. In the Bascom approach, beaches can be viewed as either
- small systems in which the rock material moves onshore, offshore, or alongshore by the forces of waves and currents; or
- geological units of considerable size. The former are described in detail below; the larger geological units are discussed elsewhere under bars. Both types can be viewed as "beaches." bars) is spreading from the incipient dune]] There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. That part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more longshore bars: slightly raised, underwater embankments formed where the waves first start to break. The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (that is, are sand), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune. The line between beach and dune is difficult to define in the field. Over any significant period of time, sand is always being exchanged between them. The drift line (the high point of material deposited by waves) is one potential demarcation. This would be the point at which significant wind movement of sand could occur, since the normal waves do not wet the sand beyond this area. However, the drift line is likely to move inland under assault by storm waves.

How beaches are formed

Beaches are deposition landforms, and are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles). Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. A coral reef offshore is a significant source of sand particles. coral reef The shape of a beach depends on whether the waves are constructive or destructive, and whether the material is sand or shingle. Constructive waves move material up the beach while destructive waves move the material down the beach. On sandy beaches, the backwash of the waves removes material forming a gently sloping beach. On shingle beaches the swash is dissipated because the large particle size allows percolation, so the backwash is not very powerful, and the beach remains steep. Cusps and horns form where incoming waves divide, depositing sand as horns and scouring out sand to form cusps. This forms the uneven edge of a sandy beach. coral reef Some beaches are artificial; they are either permanent or temporary (For examples see Monaco, Paris, Rotterdam, Hong Kong and Singapore). There are several beaches which are claimed to be the "World's longest", including Cox's Bazar, Bangladesh (120kms), Fraser Island beach, 90 Mile Beach in Australia and

Coast

Environmental importance

Human impacts

Types of coast

See also

Coastal landforms & features

Processes

Related topics & articles

Famous coasts

Ocean

Origins

Exploration

Climate

Ecology

Economy

Ancient oceans

Ocean rowing

Extraterrestrial oceans

Oceans in film

See also

External links

Headlands and bays

Geology and geography

List of some well-known headlands

List of some well-known bays

See also

External links

Shore

Stream bed

River

Topography

Biology

Pollution

Navigation

Dams

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The world's ten longest rivers

Well-known rivers (in alphabetic order)

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See also

Crossings

Transport

External links

Levee

Artificial levees

Natural levees

Levees in tidal waters

Levee breaches

Levees in popular culture

See also

External link

Ecosystem

History

See also

External link

References

Salt

Appearance

Consistency

Color

Taste

Odor

Nomenclature

Formation

References

See also

Marsh

See also

Beach

Components

How beaches are formed