A beach is a gently sloping strip of land that lies along the edge of an ocean, lake, or river. It is made up of loose sand, pebbles, and other materials. Most of the material comes from erosion of rock both near and far away from the shore. Coral reefs and other marine life also contribute sand particles to beaches.
Beaches are formed by the combination of wind and water movement, including tides. They vary in shape depending on how the waves move sand up or down the coast. They may be gentle slopes or steeper if the waves are weak.
Erosion occurs when the surface layer of a cliff or other landform is worn away by the action of waves and other weathering forces, such as tidal flow and a strong current of water flowing downhill. The erosion process can cause the land to split into layers. The top layer is called the crest, and the lower layer is the face, which slopes toward the sea. The crest is usually the highest part of a beach.
The crest forms a high ridge that slopes towards the sea, whereas the face is the flat, sandy bottom of the beach. The crest is often connected to the shoreline by a series of short, raised bars or spits. These are called barrier bars and form where a continuous period of low sea-water levels (typically in the storm season) exposes the sandbars to the tidal ebb and floods.
Coastal erosion can be caused by many factors, including natural processes such as sea-level change and the passage of large cyclonic storms (hurricanes and tropical storms). These events can redistribute sediment in such a way that beaches reconfigure in short periods.
Some people try to stop coastal erosion by building seawalls to keep sand from drifting away. However, these structures can also cause problems when they break down or are damaged by storms and waves.
When beaches become polluted, people can suffer from a variety of health problems, especially if they are exposed to toxic chemicals. Some of the contaminants found at beaches include bacteria, raw sewage, and other wastes. This can be particularly dangerous after strong storms, as these pollutants can get into the seawater and eventually wash up on the shore.
Another source of pollution is runoff from urban areas. These runoffs can contain a wide range of chemicals, such as pesticides and sewage. This can lead to disease and illness, especially in children.
Beaches have been a feature of the Earth for many billions of years. They are often found in rock formations and have been preserved by the action of waves washing on their faces.
Over time, human activities have changed the character of most beaches worldwide. Construction, pollution, climate change, and sea level rise are all causing beaches to be shaped differently than they were before. Some beach managers use beach nourishment to help beaches recover from these changes.