Some beaches are formed of crushed shells because the waves and marine currents break the shells of mollusks that inhabit these waters, reducing them to small fragments that accumulate on the shore.
Beaches made of crushed shells primarily come from marine organisms. Mollusks, crustaceans, and other shelled animals produce solid calcareous shells throughout their lives from minerals drawn from seawater. Once dead, their remains fall to the sea floor, before being stirred up and gradually reduced to fine fragments that eventually accumulate on the shores. These biological debris thus give rise to the famous clear or pink beaches, characteristic of certain regions of the world that experience great marine diversity.
The shells accumulated on the beaches are constantly subjected to repeated shocks as they bump against each other, driven by the waves and tides. Like a stone mill, these collisions cause small breaks and cracks that gradually reduce the shells to finer fragments. The sand and small pebbles mixed in act as a true abrasive, accelerating their wear and breaking them into finer grains. The wind also sometimes comes into play, hurling the debris against other hard surfaces or carrying the lighter pieces to different locations. Ultimately, over time, this process gives rise to the famous crushed shell beaches, with their distinctive granular texture.
Ocean currents and waves play a crucial role in accumulating crushed shells on certain beaches. By constantly agitating, the waves transport shell debris to the shore. Where currents are weaker, or when they encounter a natural obstacle like a bay or cove, this debris eventually settles and gradually accumulates. The rising and falling tides mix these fragments, sorting them by size and weight. The more protected the area is, the more crushed shells remain in place and form a thick layer, to the point of completely dominating the usual sand.
The climate plays a key role in the type of beach we get. For example, in regions where storms are common, the power of the waves is stronger, which breaks the shells into small fragments: beaches then become more filled with crushed shells. Where it is milder, shells often remain whole or in large pieces. The type of marine species present, depending notably on the water temperature, also directly influences the amount of shells available to form these special beaches. Furthermore, when the water is more acidic (which mainly happens due to dissolved CO₂), the calcium carbonate shell becomes more fragile, further promoting their fragmentation. Finally, natural coastal erosion and human activities (such as dredging or construction) easily change the appearance of beaches by altering the amounts of sediments or shells available.
On certain tropical islands, like the Bahamas, the pink beaches take on their unique hue thanks to seashells and fragments of broken corals mixed with white sand.
Shell Beach in Western Australia is entirely made up of tiny shells to a depth of up to 10 meters, a testament to a very unique marine ecosystem.
Crushed shells mixed into the sand play a valuable role in maintaining the chemical balance of beaches, thereby contributing to their stability by regulating the pH of the shoreline.
Some beaches can be completely renewed after a major storm, with the powerful waves from the open sea bringing new and varied fragments of shells, corals, and other marine materials back to shore.
Sure! Here’s the translation: "Yes, these specific beaches are not very common. Their formation depends heavily on the local availability of marine organisms that produce shells, as well as particular geological and marine processes that facilitate their accumulation."
The main biological sources generally come from mollusks (clams, cockles, mussels, oysters, sea snails) and, in tropical regions, sometimes also from fragile corals or other calcareous organisms.
The composition of a beach depends on the materials available locally, the surrounding biological resources, as well as the dominant erosion and fragmentation processes in a given region. Some beaches are rich in siliceous sand resulting from terrestrial rock erosion, while others benefit from an abundance of biological materials such as shells or corals.
The color of a shell beach primarily depends on the species that formed the crushed shells (biological origin colors), as well as the influence of the sun (gradual discoloration) and the degree of chemical mechanical erosion. Shell sand often varies between bright white, light beige, pink, and even light brown.
Generally no, but the comfort may be reduced compared to fine sand. It is advisable to wear suitable beach shoes to avoid cuts or small injuries on certain beaches where the shells are particularly fragmented and sharp.
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