A beach is the land along a body of water, and it’s made up of any number of materials, including sand, pebbles, cobbles, rock and shells. A beach is always changing, as material accumulates in some places and moves away in others. A beach isn’t the same all the time, either; it changes seasonally and even within a single day.
Most beaches are made of ocean sediment. Waves erode the surface of the rocky coastline, wearing it down and turning huge boulders to sand. The sand is then carried ashore in tides and currents. The upper limit of the beach is called the swash line, the point where the strongest waves no longer sort and move the sediment. The lower limit is called the beach trough and may extend to depths of a few meters.
The trough of a beach is often lined with longshore drift bars, which are slightly raised areas of sand and sediment that act as a breakwater. These bars prevent tidal currents from entering the beach, and they’re often built up with sand deposited by the powerful surf of winter storms. The sand on a beach may also be moved offshore into sandbars by the powerful surges of summer storms.
People who live near beaches frequently combat coastal erosion by building seawalls. These structures are usually made of concrete, stone, or other durable materials, and they’re designed to block sand and other beach material from blowing away in the wind and the tide. Beaches also change seasonally, as waves bury sand in the winter and retrieve it from sandbars during the summer. These seasonal changes can make a beach wide and gentle in one year, then narrow and steep in the next.
While a beach can be any type of shoreline, the term is most often used to describe a sandy shore. In some parts of the world, such as Australia and New Zealand, rocky beaches are also common, but they’re generally not considered to be beaches because their sand is too coarse to create the ideal smooth, white sand that many people seek at a beach.
A beach is a popular recreational area, but it’s important to keep it clean and protect wildlife. Pollution from trash, especially plastic, can choke or tangle marine animals such as sea anemones or crabs. It’s also important not to take shells or other living things from the beach, as this destroys habitats and can lead to health problems. In addition, pollution can prevent tidal pools from developing, which can deprive the surrounding ecosystem of essential nutrients.