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So Tell Me, Where Do All That Beach Sand Come From?

The sand you see on beaches is from broken down rocks along with some fragments of shelled sea creatures and other biomass as well as sediments from inland areas that have been ground to very fine particles, tossed up by the waves, carried by rivers and streams, and collected.

Those grains of sand under your feet are actually the result of the process described above, and decomposition that has occurred over hundreds of thousands and millions of years.

What’s more? The sand on each beach is unique to the particular beach where you find it. The sand’s unique composition, colour and grain size are a result of the source rocks it came from, but also a result of coastal processes that modify the sand over long periods of time.

A significant amount of sand particles are made of calcium carbonate, found in tiny bits of fragmented shells from sea life. Tropical regions like Nigeria, have more of this shell-derived sand than temperate regions, where the sand is mostly silica-based in the form of quartz – which could be a form of igneous, sedimentary  or metamorphic rock.

As an example, many of the beaches in Bermuda do not have only white sand, but also have pink or reddish sand particles as well. The origin of this famous colouration is the remains of tiny, single-celled creatures called Foraminifera that have pink or reddish shells.

Hawaii, meanwhile, is well-known for its black sand beaches, the result of ground-up, dark volcanic rocks. Some beaches on Hawaii’s Big Island even have a greenish tint, thanks to the presence of the mineral olivine, another product of weathered igneous or sedimentary rocks.

The sand on most beaches are also rather old, some are 5,000 years or more. Very little new sand reach the coast nowadays from inland areas as they once did. This is due to the construction of roads, dams, and sand dredging activities for building and land reclamation projects; such developments along the coastline impedes the transport of sand from the interior to the coast. Yet, this is not the only reason. 

The other major reason is that over the years, rise in sea levels have caused very large estuaries – the area of land where rivers drain into seas and oceans – to be formed. These estuaries trap would-be sand before it reaches the coast, thus reducing the quantity of sand that are washed ashore.

 

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