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Tuesday 9 April 2013

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Beach Wallpaper Definition

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A beach is a narrow, gently sloping strip of land that lies along the edge of an ocean, lake, or river. Materials such as sand, pebbles, rocks, and seashell fragments cover beaches.

Most beach materials are the products of weathering and erosion. Over many years, water and wind wear away at the land. The continual action of waves beating against a rocky cliff, for example, may cause some rocks to come loose. Huge boulders can be worn town to tiny grains of sand.

Beach materials may travel long distances, carried by wind and waves. As the tide comes in, for example, it deposits ocean sediment. This sediment may contain sand, shells, seaweed, even marine organisms like crabs or sea anemones. When the tide goes out, it takes some sediment with it.

Tides and ocean currents can carry sediment a few meters or hundreds of kilometers away. Tides and currents are the main way beaches are created, changed, and even destroyed, as the currents move sediment and debris from one place to another.

Beaches are constantly changing. Tides and weather can alter beaches every day, bringing new materials and taking away others.

Beaches also change seasonally. During the winter, storm winds toss sand into the air. This can sometimes erode beaches and create sandbars. Sandbars are narrow, exposed areas of sand and sediment just off the beach. During the summer, waves retrieve sand from sandbars and build the beach back up again. These seasonal changes cause beaches to be wider and have a gentle slope in the summer, and be narrower and steeper in the winter.

Beach Berms

Every beach has a beach profile. A beach profile describes the landscape of the beach, both above the water and below it. Beaches can be warm, and rich in vegetation such as palm or mangrove trees. Beaches can also be barren desert coastlines. Other beaches are cold and rocky, while beaches in the Arctic and Antarctic are frozen almost all year.

The area above the water, including the intertidal zone, is known as the beach berm. Beach berm can include vegetation, such as trees, shrubs, or grasses. The most familiar characteristic of a beach berm is its type of sand or rock.

Sandy

Most beach sand comes from several different sources. Some sand may be eroded bits of a rocky reef just offshore. Others may be eroded rock from nearby cliffs. Pensacola Beach, in the U.S. state of Florida, for instance, has white, sandy beaches. Some sand is eroded from rocks and minerals in the Gulf of Mexico. Most sand, however, is made of tiny particles of weathered quartz from the Appalachian Mountains, hundreds of kilometers away.

The sandy beaches surrounding Chameis Bay, Namibia, are also full of quartz and seashells. However, the beaches of Chameis Bay contain another type of rock—diamonds. Mining companies have dug mines both on the beach and offshore to excavate these precious stones. Other gems, such as sapphires, emeralds, and garnets, are present on many beaches throughout the world, as tiny grains of sand.

Rocky

Some beach berms are not sandy at all. They are covered with flat pebbles called shingles or rounded rocks known as cobbles. Such beaches are common along the coasts of the British Isles. Hastings Beach, a shingle beach on the southern coast of England, has been a dock for fishing boats for more than a thousand years.

A storm beach is a type of shingle beach that is often hit by heavy storms. Strong waves and winds batter storm beaches into narrow, steep landforms. The shingles on storm beaches are usually small near the water and large at the highest elevation.

Other types of beaches

Some beaches, called barrier beaches, protect the mainland from the battering of ocean waves. These beaches may lie at the heads of islands called barrier islands. Many barrier beaches and barrier islands stretch along the Atlantic and Gulf coasts of the United States. These narrow beaches form barriers between the open ocean and protected harbors, lagoons, and sounds.

Beaches near rivers are often muddy or soft. Soil and sediment from the river is carried to the river’s mouth, sometimes creating a fertile beach. Hoi An, Vietnam, is an ancient town that sits on the estuary of the Thu Bon River and the South China Sea. Hoi An’s soft beaches serve as resort and tourist center.

Beach berms can be many different colors. Coral beaches, common on islands in the Caribbean Sea, are white and powdery. They are made from the eroded exoskeletons of tiny animals called corals. Some coral beaches, such as Harbour Island, Bahamas, actually have pink sand. The coral that created these beaches were pink or red.

On some volcanic islands, beaches are jet-black. The sand on Punaluu Beach, Hawaii, is made of basalt, or lava that flowed into the ocean and instantly cooled. As it cooled, the basalt exploded into thousands of tiny fragments. Some volcanic beaches, such as those on the South Pacific island of Guam, are green. The basalt in these beaches contained a large amount of the mineral olivine.