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Lanikai Beach on Oahu. This gently-sloping beach face is topped by a beach crest onto which a
salt-tolerant grass ( Sporobolus virginicus) is spreading from the incipient
dune.
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Gay Head Cliffs in Martha's Vineyard
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South Beach at Katama, Edgartown, MA. This is an open ocean beach with waves that range from docile to large and dangerous.
Spectacular beach, but children must be watched closely because of wave action. Click on photo to enlarge.
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A beach, or strand, is a geological landform
consisting of loose rock particles - such as sand,
gravel, shingle, pebbles,
cobble - or even shell fragments, along the
shoreline of a body of water. Beaches occur along coastal areas, where wave or current action deposits and reworks sediments, or at the margin of land along a lake or river subject to erosion
caused by rainfall.
Components
Some geologists consider a beach to be merely a 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, and thus 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.
There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. The 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 (sand
size or smaller), 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.
Beach formation
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. Some of the whitest sand in the world, along Florida's
Emerald Coast, comes from the erosion of quartz in the Appalachian Mountains. A
coral reef offshore is a significant source of sand particles.
The shape of a beach depends on whether or not 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 face
on some sand shorelines.
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 90 Mile
Beach in New Zealand and Long Beach, Washington (which is about 30km).
Wasaga Beach, Ontario on Georgian Bay claims
to have the world's longest freshwater beach. But the longest beach in the world is in fact Praia do Cassino, a 240km long beach located in southern Brazil, near the border with Uruguay.
Beaches and recreation
In the Victorian era, many popular beach resorts were equipped with bathing machines because even the all-covering beachwear of the period
was considered immodest. This social standard still prevails in many Muslim countries. At the
other end of the spectrum are clothing-optional beaches, where swimwear and other forms of
clothing are optional.
A walk along the beach is also popular, including a long walk in the case of a long beach, for example from one seaside resort
to the next. It is customary for people to walk barefoot to the beach, because of the pleasant
feeling of sand on their soles and between their toes. The best beach walking areas typically are near the shoreline, where the
sand is wet and more comfortable to walk in. A person will also enjoy walking with their bare feet in the water.
In more than thirty countries in Europe, South Africa, New
Zealand, Canada, South America and the
Caribbean, the best recreational beaches are awarded Blue
Flag status, based on such criteria as water quality and safety provision. Subsequent loss of this status can have a
severe effect on tourism revenues.
Due to intense use by the expanding human population, beaches are often dumping
grounds for waste and litter, necessitating the use of beach
cleaners and other cleanup projects. More significantly, many beaches are a discharge zone for untreated sewage in most
underdeveloped countries; even in developed
countries beach closure is an occasional circumstance due to sanitary sewer
overflow. In these cases of marine discharge, waterborne disease from fecal pathogens and contamination of certain marine species is a frequent
outcome.
Artificial beaches
Some beaches are artificial; they are either permanent or temporary (For examples see Monaco,
Paris, Rotterdam,Toronto, Hong Kong and Singapore).
The soothing qualities of a beach and the pleasant environment offered to the beachgoer are replicated in artificial beaches,
such as "beach style" pools with zero-depth entry and wave pools that recreate the natural waves pounding upon a beach. In a
zero-depth entry pool, the bottom surface slopes gradually from above water down to depth. Another approach involves so-called
urban beaches, a form of public park becoming common in large
cities. Urban beaches attempt to mimic natural beaches with fountains that imitate surf and mask city noises, and in some cases
can be used as a play park.
Beach nourishment involves pumping sand onto beaches to improve their health. Beach
nourishment is common for major beach cities around the world; however the beaches that have been nourished can still appear
quite natural and often many visitors are unaware of the works undertaken to support the health of the beach. Such beaches are
often not recognised as artificial. Crabs are also often used to keep beaches free from trees.
A concept of IENCE has been devised to describe investment into the capacity of natural environments. IENCE is Investment to
Enhance the Natural Capacity of the Environment and includes things like beach nourishment of natural beaches to enhance
recreational enjoyment and snow machines that extend ski seasons for areas with an existing snow economy developed upon a natural
snowy mountain. As the name implies IENCE is not quite mainstream natural science as its goal is to artificially invest into an
environment's capacity to support anthropogenic economic activity. An artificial reef designed to enhance wave quality for surfing is another example of IENCE.
The Surfrider Foundation has debated the merits of artificial reefs with members torn between their desire to support natural coastal environments and
opportunities to enhance the quality of surfing waves. Similar debates surround Beach
nourishment and Snow cannon in sensitive environments.
Beaches as habitat
A beach is an unstable environment which exposes plants and animals to changeable and potentially harsh conditions. Some small
animals burrow into the sand and feed on material deposited by the waves. Crabs, insects and shorebirds feed on these beach dwellers. The endangered
Piping Plover and some tern species rely on beaches for
nesting. Sea turtles also lay their eggs on ocean beaches. Seagrasses and other beach plants grow on undisturbed areas of the beach and dunes.
Ocean beaches are habitats with organisms adapted to salt spray, tidal overwash, and shifting sands. Some of these organisms
are found only on beaches. Examples of these beach organisms in the southeast US include plants like sea oats, sea rocket, beach
elder, beach morning glory, and beach peanut, and animals such as mole crabs, coquina clams, ghost crabs, and white beach tiger
beetles.[1]
Notable Beaches
- Bondi Beach - Sydney, New South Wales, Australia
- Miami Beach - Miami, Florida, USA
- West Palm Beach - West Palm
Beach, Florida, USA
- Daytona Beach - Daytona,
Florida, USA
- Virginia Beach - Virginia
Beach, Virginia, USA
- Long Beach - Los Angeles,
California, USA
- Redondo Beach Beach - Los Angeles, California, USA
- Copacabana Beach - Rio de Janeiro,
Brazil
- Waikiki Beach - Honolulu, Hawaii, USA
Gallery
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Recreation on a California beach, first decade of the 20th century.
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See also
References
Source
- Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.
External links
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