A beach is a narrow, gently sloping strip of land along the edge of a lake, river, or ocean. It is covered with materials such as sand, rock fragments, seashells, and other debris that are the result of erosion over a long period of time. Beaches are an important natural feature that provide habitat for many plants and animals.
The process of beach formation is complex and involves several factors. The first step in the process is weathering, which is when rocks are broken down into smaller pieces by wind or water. These particles are then carried by rivers or streams and reach the coastline. The eroding action of waves against the rocks causes them to be washed away and deposited on the beach. Over a long period of time, this process can create dunes and other coastal features.
Beaches consist of a mixture of different minerals, which determine their color. For example, sand that contains quartz and feldspar will typically be light brown. Minerals like gypsum and mica are usually tan, while silica is reddish in color. The composition of a beach is also affected by the size of the sand grains. Smaller-grained sand will be softer and more fine-textured. Larger-grained sand is often coarser and may be more rough in texture. In addition, the sand on a beach can be colored by iron oxide and other substances that are released by rock weathering.
Waves are the most important factor affecting beach dynamics. They move sand in two successive phases, called the swash and backwash. The swash moves sand in a forward direction toward the shore and the backwash moves sand out to sea. The amount of sand that is moved by the waves depends on the frequency, wavelength, and energy of the waves. The strength of the tides also influences beach dynamics by influencing the amount of material that is washed up during low-energy periods and deposited during high-energy periods.
Biological activity at beaches is influenced by the type of marine life that has adapted to live in the sand and surf. Some marine algae and shellfish grow in tidal pools on ocean beaches, while crabs and other animals burrow in the sand. Birds nest on coastal dunes and sea turtles lay their eggs on ocean beaches. The beach environment is also impacted by human activities, such as littering and sewage discharge from cities.
Beaches are often contaminated with pollutants, such as sewage and other toxic chemicals that wash into the ocean from inland cities and towns. These pollutants can harm the marine life that lives on or near the shore, including fish, shrimps, crabs, and seaweed. Sometimes these pollutants wash up on a beach after a strong storm, when sewage or garbage is washed up by waves or by the ebb and flow of the tides. These pollutants can be harmful to humans, as well. This is why some beaches are closed after a severe storm.