tsunami

or seismic sea wave or tidal wave

Catastrophic ocean wave, usually caused by a submarine earthquake. Underwater or coastal landslides or volcanic eruptions also may cause tsunamis. The term tsunami is Japanese for “harbour wave.” The term tidal wave is a misnomer, because the wave has no connection with the tides. Perhaps the most destructive tsunami ever occurred in 2004 in the Indian Ocean, after an earthquake struck the seafloor off the Indonesian island of Sumatra. More than 200,000 people were killed in Indonesia, Thailand, India, Sri Lanka and other countries as far away as Somalia on the Horn of Africa.

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Electricity produced by turbines operated by tide flow. Large amounts of power are potentially available from the tides in certain locations, such as Canada's Bay of Fundy, where the tidal range reaches more than 50 ft (15 m), but this potential power is not continuous and varies with the seasons. The first working modern tidal power plant was built in France in 1961–67 and has 24 power units of 10,000 kilowatts each.

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Level muddy surface bordering an estuary, alternately submerged and exposed to the air by changing tidal levels. In addition to the alternating submergence and exposure, the varying influences of fresh river water and salty marine waters cause physical conditions to vary more widely than in any other marine environment. The mud of a tidal flat is usually rich in dissolved nutrients, plankton, and organic debris, and it supports large numbers of small animals such as crabs and worms. Vegetation is generally sparse, but mats of blue or blue-green algae (see cyanobacteria) may be present.

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Partly enclosed coastal body of water in which river water is mixed with seawater. An estuary is thus defined by salinity rather than geography. Many coastal features designated by other names are in fact estuaries (e.g., Chesapeake Bay). Some of the oldest continuous civilizations have flourished in estuarine environments (e.g., the land between the Tigris and Euphrates rivers, the Nile delta, the Ganges delta, and the lower Huang He valley). Cities such as London (River Thames), New York (Hudson River), and Montreal (St. Lawrence River) developed on estuaries and became important commercial centres.

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Estuary on the Bay of Biscay, southwestern France. Formed by the confluence of the Garonne and Dordogne rivers, it extends for about 45 mi (72 km) inland. It is navigable for oceangoing vessels, although it has sandbanks and strong tides.

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A tidal creek is the portion of a stream that is affected by ebb and flow of ocean tides, in the case that the subject stream discharges to an ocean, sea or strait. Thus this portion of the stream has variable salinity and electrical conductivity over the tidal cycle. Due to the temporal variability of water quality parameters within the tidally influenced zone, there are unique biota associated with tidal creeks, which biota are often specialised to such zones.

In British English (and also in many other countries in the Commonwealth), a creek is a tidal water channel. In parts of Somerset, the name Pill is given to a creek; and Pill is used in certain place names, such as Huntspill. Creeks may often dry to a muddy channel with little or no flow at low tide, but often with significant depth of water at high tide. In India the term also applies to the salt water inlets enclosed by mangroves. Creeks are found dispersed all along the Indian coast. In the Florida Keys, a creek is a narrow channel between islands.

Examples

There are hundreds of examples of tidal creeks throughout the world. A few specific ones are:

• Burn of Ayreland, Mainland, Orkney
• Americano Creek, California, USA

See also

• Estuary
• River delta