The Science of Sand and What You Need to Know
Do you want to blow your kids' minds? Ask them this: Is sand called sand because it is found between sea and land? Okay, we're not really sure about that one but here are a few facts we do know about the science of sand. Next time you're on the beaches of Emerald Isle, North Carolina, you can ponder these things and share what you've learned with your family and friends. The life of sand video at the end of this post is really cool, too—so don't miss it. Sand is absolutely amazing!
"In every curving beach, in every grain of sand, there is a story of the Earth."
SAND IS A TECHNICAL TERM DEFINED BY SIZE
Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt. Sand grains are between the size of gravel grains (which is from 2 mm to
64 mm) and the size of silt (which is around 0.0625 mm to 0.004 mm).
Most sand is found on beaches and in deserts. The most common sands are
made of silica (silicon dioxide). Calcium carbonate is the
second most common.
SAND IS GEOGRAPHY
Sand comes from many locations, sources, and environments. Sand forms when rocks break down from weathering and eroding over many, many years. Rocks take time to decompose, especially quartz (silica) and feldspar. Often starting thousands of miles from the ocean, rocks slowly travel down rivers and streams, constantly breaking down along the way. Once they make it to the ocean, they further erode from the constant action of waves and tides.
SAND IS A GRAVEYARD
Sometimes sand is a graveyard full of dead bodies. Sand can consist of tiny organisms whose skeletons litter the bottom of the ocean. Or sand can be almost entirely made of coral fragments. The beach sand on tropical islands often looks white because it is made up of calcium carbonate, which comes from the shells and skeletons of reef-living marine organisms including corals, mollusks and microorganisms.
SAND IS COLORFUL
The tan color of most sand beaches is the result of iron oxide, which
tints quartz a light brown, and feldspar, which is brown to tan in its
original form. Black sand comes from eroded volcanic material such as
lava, basalt rocks, and other dark-colored rocks and minerals, and is
typically found on beaches near volcanic activity. Black-sand beaches
are common in Hawaii, the Canary Islands, and the Aleutians. Bermuda's pleasantly pink beaches results from the perpetual decay of single-celled, shelled organisms called foraminifera.
SAND IS SOMETIMES... POOP
The famous white-sand beaches of Hawaii actually come from the poop of parrotfish. The fish bite and scrape algae off of rocks and dead corals with their parrot-like beaks, grind up the inedible calcium-carbonate reef material (made mostly of coral skeletons) in their guts, and then excrete it as sand. At the same time that it helps to maintain a diverse coral-reef ecosystem, parrotfish can produce hundreds of pounds of white sand each year. Your kids will love this one, right?
THE SAND OF EMERALD ISLE, NORTH CAROLINA
Quartz (silicon dioxide), feldspar and shells are the most common materials on North Carolina beaches. You also can find sand-sized pieces of other minerals, including magnetite and garnet. Patches of pea gravel are common along the Southern Outer Banks beaches. These areas of pea-sized quartz, with a few shell fragments mixed in, are locations of old river channels. As barrier islands migrate, these sections of old river bottom are exposed and moved around. Small areas of shell hash, where shards of seashells predominate, can be found up and down the North Carolina coast. These biogenic features are created by a combination of waves and currents. Be sure to bring a magnifying glass and take a closer look at the beauty of the sand on the beach next time you're here.