In the United States, sandy beaches are a popular recreation and economic activity. Millions of people enjoy spending time on the beach, sunbathing, playing, and swimming. Some beaches even feature hotels, showers, and changing rooms. Others have lifeguard posts and shacks.
Sand is a natural material that has been eroded from offshore rock, or from local cliffs. Most of it is made from tiny particles of weathered quartz from the Appalachian Mountains. Some beaches contain seashell fragments and diamonds. Some beaches are extremely polluted, with sewage and toxic chemicals. These contaminants can lead to a variety of health issues. The BEACH Act (Beach and Ocean Act) has been established to protect beaches in the United States.
The composition of a beach depends on the sediments that are carried upstream of the beach. Some beaches are influenced by storms, while others are impacted by seasonal changes. The wind may carry sand from the inland area into the surf zone, creating a sandbar. The currents that move sand and other debris can carry it hundreds of miles.
During the winter, sand is deposited by storms, and winds can distribute it inland. This sand, or overburden, can be harmful for residents and animals. It can also change the habitat and introduce foreign fauna into the area. This overburden can cause a beach to become less stable. It can bury or change sea grasses, affecting the habitat of those species.
When waves crest, they create an area called a longshore drift. These beaches are often narrow and gently sloping, and they are characterized by a crest of sand that is followed by a wave backwash. These waves can also be destructive, if the period between crests is short. The crest of sand on the beach can then be worn away, exposing less resilient rocks and soils.
During the summer, the beach can be broad and wide, with strips of sand forming a beach sand bank. The sand will move along the beach, and may even travel southward as the ocean currents move it. The crest of sand on a beach sand bank may be covered with flat pebbles, known as shingles. Some beach berms are not sandy, but are composed of rocks. The face of a berm can have a trough or shore bar, which provides a protective barrier for the sand.
Depending on the type of waves, the shape of the beach may vary. During a freak wave event, the beach can be significantly altered, carrying large volumes of sand and shifting the location of the beach. The energy of the wave can also affect its appearance.
Storms can also erode a beach. This can be especially harmful for communities living near a beach. The waves can carry sand and other debris from the inland area, and it can destroy flora. Some sand is eroded from nearby cliffs, and some is carried by the currents. A beach sand bank can be very unstable, and it can be carried out into permanent water.