coast

 

land bordering an ocean or other large body of water. The line of contact between the land and water surfaces is called the shoreline. It fluctuates with the waves and tides. Sometimes the terms coast and shore are used synonymously, but often shore is interpreted to mean only the zone between the shorelines at high tide and low tide, and coast indicates a strip of land of indefinite width landward of the shore. Classically, coasts have been designated as submergent if they resulted from a rise in the relative sea level and emergent if they resulted from a decline. Young submergent coasts usually are irregular and have deep water offshore and many good harbors, either bays or estuaries. Much of the coast of New England and most of the Atlantic coast of Europe are young submergent coasts according to this classification scheme. Gradually the submergent coast, subjected to erosive attacks of the ocean and other agents, becomes mature. Headlands are worn back to form cliffs, at the base of which deposits of eroded material accumulate as fringing beaches; spits and bars also grow up from material that is carried by currents and deposited in deeper water. The shoreline is called mature when it is smooth, the headlands having been cut away and the bays either filled up or closed off by spits. Emergent shorelines usually have shallow water for some distance offshore. Such shorelines are found along the Atlantic coast of the SE United States and along part of the coast of Argentina, near the Río de la Plata. This classification system does not adequately describe many coasts, partly because many of them exhibit features of both submergence and emergence. Because of these and other problems a classification system that is based on the most recent and predominant geologic agent forming the coast has become popular. Under this scheme, there are essentially two major types of coasts. Primary coasts are youthful coasts formed where the sea rests against a land mass whose topography was formed by terrestrial agents. These coasts include land erosion coasts (Maine), volcanic coasts (Hawaii), deposition coasts (Nile Delta coast), and fault coasts (Red Sea). Secondary coasts are formed chiefly and most recently by marine agents, and may even be primary coasts that have been severely modified by wave action. These coasts include wave erosion coasts, marine deposition coasts, and coasts built by organisms (reefs and mangrove coasts). The nature of the coastline of a country or a state is an important factor in its economic development because it relates to defense, fishing, recreation, and overseas commerce.

Bibliography

See C. A. M. King, Beaches and Coasts (2d ed. 1972).

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 to, or associated with a coast.

Coast is a specific term, and is 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, requiring government agencies to make frequent use of beach cleaners and other volunteer cleanup efforts. 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 sunbathing. Growth management can be a challenge for coastal local authorities who often struggle to provide the infrastructure required by new residents seeking seachange lifestyles.

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 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

An emergent coastline is a coastline which has experienced a fall in sea level, because of either a global sea level change, or local uplift. Emergent coastlines are identifiable by the coastal landforms, which are above the high tide mark, such as raised beaches. Alternatively, a submergent coastline is a coastline which has experienced a rise in sea level, due to a global sea level change, local subsidence, or isostatic rebound. Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as rias (drowned valleys) and fjords.

A concordant coastline is a coastline where bands of different rock types run parallel to the shore. These rock types are usually of alternating resistance, so the coastline forms distinctive landforms, such as coves. A discordant coastline is a type of coastline formed when rock types of alternating resistance run perpendicular to the shore. Discordant coastlines feature distinctive landforms because the rocks are eroded by ocean waves. The less resistant rocks erode faster, creating inlets or bays; the more resistant rocks erode more slowly, remaining as headlands or outcroppings.

Coastal landforms and features

The "Cliff erosion" features erode to form the feature below in the list; [Eg. a Cliff erodes to form a cave, which erodes to become an arch...]

Cliff erosion

• cliff
• cave
• Arch — archipelago
• stack
• stump

• cape
• Peninsula
• Gulf
• headland
• bay
• cove

• Wave cut cliff
• wave cut notch
• wave cut platform

Rivers on the coastline

• Estuary
• delta

Coastal features formed by sediment

• bar
• barrier island
• beach
• boondock
• shoal
• dune system
• Mud flat
• spit
• Surge channel
• Tombolo
• Raised beach — ria

Coastal features formed by another feature

• Salt marsh
• Lagoon

Other features on the coast

• Concordant coastline
• Discordant coastline
• Fjord
• Island — island arc
• Machair

Coastal processes

• Attrition
• Currents
• Denudation — Deposition
• Erosion
• Flooding
• Longshore drift
• Saltation — sea level change (eustatic — isostatic) — Sedimentation — sediment transportation — Solution — sub-aerial processes — Suspension
• Tides
• Waves — Weathering

Wildlife

Animals

Animals living along the coast vary enormously, some live along coasts to nest like puffins, sea turtles and rockhopper penguins. Sea snails and various kinds of barnacles live on the coast and scavenge on food deposited by the sea. Most coastal animals are used to humans in developed areas, such as dolphins and seagulls who eat food thrown for them by tourists. Since the coastal areas are all part of the littoral zone, there is a profusion of marine life found just off-coast.

There are many kinds of seabirds on the coast. Pelicans and cormorants join up with terns and oystercatchers to forage for fish and shellfish on the coast.

Plants

Coastal areas are famous for their kelp beds. Kelp is a fast growing seaweed that grows up to a metre a day. Corals and anemones are true animals, but live a similar lifestyle as plants do.

See also

• Coastal erosion
• List of countries by length of coastline
• Coastal management
• Coral reefs
• Earth science
• Engineering geology
• Geography — Geology — Geomorphology
• How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension
• Land reclamation
• Marine biology
• Marine life
• Nautical chart
• Ocean

External links

• UK Coast Guide
• Preserving the coasts

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