Summer won’t be complete without taking a trip to the sandy shores of the beach. Very few things can compare to swimming in the cool blue waters, breathing in that humid sea air, and feeling the sand between your toes. On that note, have you ever wondered why is there sand on beaches? Maybe you haven’t and maybe you don’t care, after all, you didn’t come to the beach to while away your time pondering about such tiny details. But just in case you’re wondering, here’s why.
So Why Is There Sand on the Beach?
Sand is basically the material that results from the breakdown and weathering of rocks and other sediments over thousands and millions of years that the earth has existed. The sandy beach as a whole is a combination of all these materials, though some sediments may be more abundant than others depending on the type of sand particles that were washed ashore. The exact composition of sand can vary greatly depending on local mineral sources and geological conditions.
Sandy beaches are formed predominantly as a result of wave action, or simply put, waves and currents moving towards the land. These waves and currents carry with them loose sediments and sand particles, which are then deposited on land. As mentioned earlier, these sediments and sand particles can be a lot of things, from eroded offshore rocks to decomposing corals underwater.
It should be noted that sand grain refers to the rock particles that have a diameter between 0.0625mm to 2mm. Anything smaller and it would be considered as silt, and if it were bigger then it would be a gravel. Cool stuff, huh?
Types of Sands in Beaches
Not all sands are created equal, and there are actually different types of sands in beaches as they come in a wide variety of colors and textures. In fact, experts say that sand can be classified in a myriad of ways, but the most common way of doing so is according to its location since all of the types of sand have different origins depending entirely on their geological conditions.
White Sand Beaches
White sand beaches are perhaps the most popular destination among all the other types of beaches in the world. There’s something about that glistening, powdery stretch of sand that makes them a wonder to walk on and behold.
White sand beaches are white basically because they’re mostly composed of ground-up quartz. Actually, all beaches have quartz in them, it’s just that they’re smaller in quantity which is why they’re of another color instead of white. Quartz is similar to silica in chemical composition but the structure can be quite different.
Aside from quartz, reports say that there is another reason why white sand beaches are, well, white. Accordingly, the white grains that are mixed with quartz in white sand beaches are actually fish poop. To be more specific, parrotfish poop. Careful where you lay your beach blanket now.
It appears that this fish has a penchant for algae growing on corals and as they nibble about, they tend to ingest bits and pieces of the coral as well. Naturally, after being digested and all, the parrotfish will have to excrete whatever remained of their meal. Believe it or not, these come out in the form of white powder which are washed ashore by the waves. And another fun fact: a single parrotfish can produce hundreds of pounds of ‘sand’ a year.
Black Sand Beaches
Black or gray sand beaches may not appear to be as pretty as white sand beaches, but they do have their own charm and many globetrotters around the world have found them just as enjoyable for a beach vacation.
Black sand beaches are composed of a variety of materials like magnetite and hornblende to name a few. These minerals are often transported to the beach by rivers, which is also one reason why riverbanks usually have black sand. In beaches near volcanoes, the black sand grains are most likely to be minute pieces of lava and basalt which is produced by volcanic eruptions.
Green Sand Beaches
The green color of the sand can be attributed to several factors, but the most agreed upon factor would be the presence of olivine crystals.
Olivine crystals are those green glassy crystals formed inside volcanoes and comes out with the lava. Because these crystals are much heavier and denser, they tend to stay and accumulate on shore instead of being swept out into the sea. However, there are other green minerals that may possibly contribute to the green color in the sand like malachite and serpentine. Again, this will depend on the geological conditions near the beach.
Some tourists may complain that green sand beaches do not look ‘green’ at all, and perhaps they’re right because the sand looks more like a dull olive color. Still, they’re quite interesting because there are only four of them in the world accordingly. Some say that there are actually less, but hey, let’s leave the argument to the experts.
Red Sand Beaches
Red sand beaches (sometimes pink) are also quite rare, though it seems that they’re more common than green sand beaches. The reddish color of these beaches are often attributed to high iron content in the sand. For instance, the Kaihalulu Beach in Maui is surrounded by hills that are rich in iron, thus giving the beach that deep dark red color.
Some red sand beaches attribute their color to high amounts of garnet instead of iron. Garnet usually comes from either metamorphic or igneous rocks and you’ll usually find a significant number of these rocks near red sand beaches. Actually, many beaches have garnet in them, though in small quantities so that they aren’t able to influence the color of the beach. However, there are some beaches where high concentrations of garnet make up the total sand composition of the beach.
Abiogenic and Biogenic Sand
As mentioned earlier, sand is formed as a result of weathering and erosion. Those sand grains which are formed as a result of these processes are referred to as abiogenic sand.
Biogenic sand, on the other hand, is composed of exoskeleton or bone fragments of dead fish, corals and other sea creatures. That said, there are many different organisms that can contribute to the formation of this sand type. Because of that, it should be noted that biogenic sand may differ from place to place, mostly influenced by the kind of marine life available in the area.
Biogenic sand is usually light-colored and its components are made of carbonate material, although some organisms maybe silica. Important source material of biogenic sand are the remains of clams, sea snails, foraminifera, algae, corals, echinoids, sponges, and others.
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Let’s admit it, we don’t usually pay attention to sand, unless perhaps they get into our hair or our eyes. But despite being a seemingly ordinary everyday thing, sand can be quite interesting. And though the question “why is there sand on beaches” is not as common as “why is the sky blue” it’s still pretty cool to actually know why and have an answer ready just in case somebody suddenly decides to ask.
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