A beach is land along the edge of a body of water, such as a lake or ocean. It may consist of sand, cobbles, rocks, mud, or shells. Some beaches are narrow and gentle, while others are wide and steep. Besides being a great place for a day in the sun, sandy beaches are important habitats for many species of birds, mammals, and sea turtles.
The shape of a beach is largely determined by the waves that form it. Ocean currents move sediment from inland areas to the coastline. These materials can travel hundreds of kilometers to the beach. They can also be carried by the wind. If they get stuck, the ocean currents can carry them back offshore. Eventually, they can form a barrier reef. This is a thin, sediment-covered barrier separating a lagoon from the open sea. Normally, the reef is anchored on compact clay or submerged bedrock. Occasionally, the reef is cut into pieces by tidal inlets.
Beaches can be as wide as a football field, and as shallow as a pond. During a storm, fine-grained material can be seen on the beach. Although these materials are not visible on a beach for long, they are an indication of a storm. The finer the grain, the better a beach’s ability to absorb water.
The shape of a beach depends on the direction and speed of the waves. When the waves are breaking, they trap air bubbles and form a ripple. When the tide goes out, the ripples are exposed. These ripples are an indication of where a stream has flowed across the beach.
Beach cusps are a horn-like feature that deflects the swash of a wave. In general, they are evenly spaced and are positioned near the high tide level. During tidal cycles, beach cusps can vary in shape, size, and frequency, but they are always present.
One of the most obvious differences between a rip current and a beach cusp is that the rip current flows offshore. The rip current can reach speeds of up to two meters per second. However, these rip currents don’t cause physical discomfort. Rather, the fastest way to avoid a rip current is to swim toward the beach and find a lifeguard. You can also raise your arm to signal for help. For some people, the only time they realize that they are in a rip current is when the wave suddenly disappears. To stay safe, swimmers should swim in a safe swimming area, such as those marked by yellow or red flags.
Beaches are shaped by ocean currents, as well as by weather systems. As a result, they are constantly changing. Each tidal cycle uncovers new features. The beach of Tuvalu was rapidly eroding in the 1990s. Now, the island nation has developed a series of seawalls to prevent further erosion.
Seawalls are also built to keep beach materials from drifting away. In some places, they are made of rock, concrete, or plastic.