Beaches are long, narrow, gently sloping zones of sand and gravel on the edge of a body of water. They are a result of natural processes and human activity. Ocean currents are the main source of beach sand.
The ocean’s waves erode the shoreline, removing sand and rocks. They also carry debris, such as shells, in their wake. Depending on the wave energy and the size of the particles, the beaches can be fine, coarse, or wide. Depending on the material, the sand can be sandy, gravel, pebbles, or sandstone. Most beach sands are quartz, feldspar, or calcite. Other materials include seashell fragments, plastic, and broken glass.
When the tides go out, the intertidal zone of a beach is exposed. This area is a dynamic and ever-changing zone of plants and animals that move up and down the beach according to the water level. Animals such as sand crabs, beetles, and clams form an array that travels up and down the beach.
Sea level has risen over the last few decades and many beaches are now drowned. However, these changes are a result of an invisible force. Human activity has accelerated the natural process. In some cases, beach sand has been removed from beaches for concrete and construction.
Sandy beaches play important cultural and recreational roles. They often have lifeguard posts, shacks, or hotels. Some are covered with shells and coral. Others have man-made infrastructure, such as pools, showers, and even changing rooms.
Beaches are typically some shade of brown. Their color is a result of the minerals in each grain of sand. Darker coloured minerals are heavier than light coloured ones. If there is a uniform source of sand, the colour will be uniform, but on beaches where the source is mixed, the sand will vary in colour. Likewise, the colour of the rocks is dependent on the geology of the surrounding area.
Beaches are created by the interaction of the waves, the wind, and ocean currents. There are two main kinds of beaches: foreshore and offshore. Foreshore is the part of the beach most affected by breaking waves. During calmer weather, sand is deposited at the foreshore. During storms, the foreshore is eroded, and sand is carried offshore.
Coarse sand beaches tend to pile up sand in a steep slope. Fine sands have more gentle slopes and have better absorption capacity. Sands are transported by the surf and longshore drift. Generally, the sand moves inland when the water level is low, and then moves landward when the water level rises.
Beaches are always changing. Each tidal cycle reveals new features. These features are a result of the varying energy of the waves, the size of the sediments, and the state of compaction. A large swell can move sand and rocks from one end of the beach to the other. Likewise, when the tides are high, sand is pushed up the beach. Eventually, it leaves the beach to drain into a submarine canyon.