Coastal environments

• Abrasion


  A type of erosion in which rock fragments carried by waves grind away a surface such as a cliff face.
• Attrition


  The process by which particles of rock being transported by the sea are rounded and become smaller in size due to hitting one another. Particles near the shoreline become smaller and more rounded due to more frequent attrition.
• Backwash


  The movement of water back down the beach due to the effect of gravity.
• Constructive wave


  A wave with a long wavelength and a low height, which helps to build up beaches by deposition
• Corrosion


  The process by which the minerals in a rock, notably calcium ions, are dissolved in acid water.
• Solution


  The process by which the minerals in a rock, notably calcium ions, are dissolved in acid water. It is also referred to as corrosion.
• Deposition


  The laying-down of material carried by the sea because of a loss of energy, often caused by increased friction with vegetation of coarse particles.
• Destructive wave


  A wave with a high height and a short wavelength, which helps erode beach materials and cliffs. Erosion is the wearing away of the Earth's surface by a moving agent, such as a river, glacier or the sea. In a river, there are several processes of erosion, including hydraulic action, abrasion, attrition and solution. In coastal areas, hydraulic action is the most potent form of erosion.
• Fetch


  The distance of open water over which wind can blow to create waves. The greater the fetch the more potential power waves have when they hit the coast. In the south and west of England the fetch stretches for nearly 6000 km, to South America.
• Hydraulic action


  The erosive force exerted by water. It is particularly effective on jointed rocks, especially during storm conditions.
• Prevailing wind


  The direction from which the wind most commonly blows in a region. In the British Isles, for example, the prevailing wind is southwesterly, blowing from the Atlantic Ocean and bringing moist and mild conditions.
• Sea level


  An average level of the sea, between high water mark and low water mark.
• Swash


  The movement of material up the beach in the direction of the prevailing wind.
• Wave


  A circular or elliptical movement of water near the surface of the sea.
• Wave refraction


  The way in which a wave changes shape and loses speed as it comes in contact with the seabed. If refraction is complete, waves break parallel to the coastline. If refraction is not complete, longshore drift occurs.
• Arch


  A natural bridge-like feature formed by erosion. Arches are formed from the erosion of a headland where two caves meet and break through the headland.
• Bar


  A depositional feature: a long sandy ridge running parallel to a coastline that is submerged at high tide. Some bars develop as offshore bars whilst others form from the development of a spit across the whole of a small bay.
• Bay


  A wide, open, curving indentation of the sea.
• Beach


  A feature of coastal deposition, consisting of pebbles sand. It is usually defined by the high and low water marks.
• Coastal cave


  Formed where relatively hard rock containing lines of weakness is exposed to severe wave action.
• Cliff


  A rock-face along the coast, where coastal erosion, weathering and mass movements are active and the slope rises steeply (over 45 º) and for some distance. The nature of the cliff depends on the nature of the rocks and their hardness and jointing pattern.
• Headland


  A point of land projecting into the sea, also known as a cape or promontory.
• Offshore bar


  A linear ridge of sand or pebbles parallel to the shoreline. Offshore bars are formed when waves disturb sediments on the seabed and form them into a submarine ridge or bar.
• Salt marshes


  Marshland with salt-tolerant vegetation. Salt marshes develop around estuaries and on the sheltered side of spits. Salt marshes usually have a network of creeks and channels by which sea water enters and leaves the marsh.
• Sand dune


  A mound or ridge of wind-drifted sand common on coasts and in deserts. In coastal areas, sand is trapped by vegetation, notably sea couch grass and marram grass, to form stable dunes.
• Spit


  A ridge of sand or shingle connected to the land at one end and in the open sea at the other end. It is formed by the interruption of longshore drift due to wave refraction, river currents, secondary winds and/or changes in the shape of the coastline.
• Stack


  An isolated upstanding pillar of rock that has become separated from a headland by coastal erosion. It is usually formed by the collapse of an arch.
• Stump


  An eroded stack, which is exposed only at low tide.
• Tombolo


  A bar that links an island to the mainland
• Wave-cut platform


  A gently sloping rock surface found at the base of a coastal cliff. It is covered by water at high tide but exposed at low tide. It is formed by the erosion (by waves) of a former cliff face.
• Coral


  A living organism (polyp) living in clear, tropical waters. Corals live in communities known as reefs. They secrete lime and build a skeleton.
• Atoll


  A coral reef surrounding a central lagoon, which may have developed around volcanic islands that have submerged or may have developed upwards as sea levels have risen.
• Barrier reef


  A coral reef running parallel to the coastline and separated from the shoreline by an extensive lagoon system.
• Fringing reef


  a coral reef attached to the coastline.
• Patch reef


  A small circular or irregular reef that rises from the sea floor of lagoons behind barrier reefs or within atolls.
• Coral bleaching


  The expulsion of the algae from coral causing it to lose colour.
• Zooxanthellae


  Algae that live in a symbiotic relationship with coral and give it its colour.
• Coastal protection


  Refers to measures taken to prevent coastal erosion and/or flooding. To reduce erosion, several different forms of coastal protection are used. These can be divided into soft engineering and hard engineering.
• Gabion


  A wire basket filled with rocks or stones used for stabilising slopes and protecting the base of cliffs in areas of coastal erosion.
• Groyne


  A wooden or concrete barrier built at right-angles to a beach in order to block the movement of material along the beach by longshore drift. Groynes are usually successful in protecting individual beaches. However, as they prevent beach material from being transported along the coast they can starve beaches further down the coast of sand and shingle; hence these beaches may be at increased risk of wave erosion.