A beach is a body of land that stretches out into the water. It is made up of accumulated material that is deposited by tides and waves. Beaches vary widely in size and shape, ranging from wide and sandy to steep and rocky. Some are covered in shells, while others are devoid of any. Over time, the width of a beach may change, and the sand may shift or become uneven. Beaches may also be characterized by rocks and tree stumps.
Sand is made of small particles of rocks that are carried to the beach by the wind and water. The colors of these grains depend on the surrounding geology, but most beaches are a shade of tan or brown. Extreme colors may be seen on a particular beach, as the sands are pulverized by natural forces.
A variety of animals and plants live on beaches, including crabs, sea grasses, and birds. These animals feed on the materials left behind by waves, and some of them may nest and lay eggs on the sand. Several species of sea turtles nest on beaches, as do seals and sea lions. Other animals such as clams and starfish also use the sand as a nursery. In addition, various rays feed on sand bottoms. Some sharks use electrical sensing to detect prey.
The composition of sand on a beach changes seasonally and hourly. Storm winds toss sand into the air and make sandbars. Sandbars are narrow exposed areas of sand, which are often eroded by waves. During summer, waves retrieve the sand from these sandbars and build up the beach. During the winter months, the sandbars are narrower and more steep than in summer.
A beach has many types of sand, rocks, and seashell fragments. Beaches can range from dozens of kilometers long to only a few feet wide, depending on the size and location of the body of water. The majority of beach materials are products of weathering. Water and wind have worn away land over many years. Huge boulders can be eroded down to sand grains.
Another problem threatening beaches is sea level rise. The ocean has been rising for years, and rising seas have completely destroyed some beaches. In 2010, rising sea levels in the Bay of Bengal swept away New Moore Island, a strip of sandy beach in the middle of the bay. A small island in the area was claimed by Bangladesh and India, and this uninhabited island was completely drowned by rising sea levels. Beaches can also be affected by human activity, such as construction of dams and coastal development.
The most dynamic area of a beach is the surf zone. When waves reach a depth of 1.5 times the wave’s height, they break. The waves then move shoreward as broken white water. Breaking waves may also be deflected longshore and may form rip currents.