Beach Sand and Shells

Beach Sand and Shells

Sand is a loose granular material blanketing the beaches, riverbeds, and deserts of the world.  While sand is composed of different materials that vary depending on location, it also comes in an array of colours including white, black, green and even pink.  The most common component of sand is silicon dioxide in the form of quartz. Generally, the Earth’s landmasses are made up of rocks and minerals.  As a result, the weathering processes such as wind, rain and freezing/thawing cycles — break down these rocks and minerals into smaller grains.

Unlike some other minerals, quartz is hard and is insoluble in water and doesn’t decompose easily from the weathering processes. Streams, rivers, and wind, transport quartz particles to the seashore where the quartz accumulates as light-colored beach sand.

For instance, tropical islands, such as the Hawaiian Islands, don’t have a rich source of quartz, so the sand is different in those locations. The beach sand on tropical islands often looks white because it is made up of calcium carbonate. As a rule, this comes from the shells and skeletons of reef-living marine organisms.

For the most part, sand forms when the reef breaks down, either by mechanical forces, such as waves and currents or from bio-erosion caused by grazing fish, urchins and other marine life. The famous pink sand of Bermuda is also composed of eroded calcium carbonate.  As a result, sand gets its ruddy hue from the abundant red foraminifera.

Generally beaches such as Denarau Island in Fiji have black sand, which is composed of black volcanic glass. Sometimes, erosive forces separate the mineral olivine from other volcanic fragments, leading to green sand beaches, such as Hawaii’s Papakōlea Beach.

Beach Sand & Shell Particles

Regularly, beach sand and shell particle size depends on how far from the origin the beach sediment is and what it is composed of.  If the beach has pebbles, then the source isn’t that far away.  Whereas sandy beaches require the sediment to weather more before being found at the beach.  For example the further away you are from the source of water, such as mountain tops, the finer the particles will be.  Sometimes, large but short storms provide enough energy to transport larger particles further away from the source, giving pebbles with sand.

Sea Shell Types

For instance, seashells are a major source of organic deposits on the seafloor and make up the majority of limestones and chalks.  There are so many sea shell types that scientists place them in seven classes.
  • Gastropoda – gastropods (snails, whelks, cowries, etc.)
  • Bivalvia – bivalves (cockles, clams, scallops etc.)
  • Scaphopoda (tusk shells)
  • Aplacophora (worm-like mollusks)
  • Polyplacophora (chitons)
  • Monoplacophora (cap-like shells bearing one plate) and
  • Cephalopoda (nautiluses, octopuses, squids etc).

Most seashells fall into the category of gastropods and bivalves.

Exactly What Is a Seashell?

Generally, most seashells come from mollusks, a large group of marine animals including clams, mussels, and oysters.  These marine animals exude shells as a protective covering.  Subsequently, they are made up of mostly calcium carbonate. As the animal ages, the shell gets larger and more calcium carbonate is exuded from the mantle.  Therefore, colour patterns are specific to different species making it relatively easy to tell different species apart.

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