A beach, also called a shoreline, is the land area surrounding a body of water. It may include sandy beaches, which are a popular tourist destination, or rocky coasts, which are more common in tropical regions.
Beaches vary in size and shape, depending on a number of factors such as wave parameters, tide height and the sediments they contain. In general, the beach profile consists of a crest (top) and a face that slopes toward the water. The face may extend down to the water level and, above it, a terrace surface may be developed.
The sand on the top of the beach face is usually finer and more compact than the sand below it. The sand on the bottom of the beach is often coarser, and may be composed of broken shells or other hard objects. The beach profile also varies in the amount and distribution of wave scour, which is the erosion of fine sediments by strong waves.
Sediment transport is essential to the continued existence of a beach. It is transported from points where the sediment first appears on the beach, such as a river or stream, to areas lower down on the beach profile where the waves are not as intense or the tide is receding faster than it is rising. The sand and other sediments carried forward from lower down the beach profile will settle, consolidate and compact when the succeeding wave crest arrives. The sediment that is not settled will be blown off the beach by subsequent waves and will become more susceptible to the scouring effects of the longshore currents or receding tides.
Sand is a type of natural material that can come in various colors, depending on the geology of the area it is in. For example, in Hawaii, much of the sand on the beaches is black basalt because of volcanic eruptions nearby. The sands in other areas may be white, tan, yellow or other colors that are derived from the sediments of coral, sandstone, quart or other rocks eroded by the sea.
In oceans and large lakes, waves ebb and flow on the upper part of the beach profile, creating a series of ridges that are called berms or crests. These crests are sloping and sometimes convex seaward, so that they form a terrace surface.
As a result, the sand forming the crest of a berm is displaced seaward along the crest to form the beach face, which continues the crest’s slope down to the water’s edge. The lower part of the beach face is a wide area of sand that includes a few parallel offshore bars.
The crest and the face of a beach berm are often connected by a trough that is a feature of the upper part of the crest. A trough is a depression or ledge that is the result of the turbulence that is caused by the waves on the beach.
A berm can be a very conspicuous feature of a beach and is a depositional feature. The sand that makes up a berm is usually the result of sand moving in from offshore during quiet weather.