Moment of Science: Sand

“In every curving beach, in every grain of sand, there is a story of the Earth.” -Rachel Carson
From combing the desert, to chilling on the beach... Dan Smith never shies away from good science, but this week, he's burying his head in the sand. 🏖️
Published: Nov. 15, 2022 at 3:22 PM EST
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In the immortal words of Anakin Skywalker: “I don’t like sand. It’s coarse and rough and irritating and it gets everywhere.” As annoying as all that grit can be sometimes, it can have some surprising benefits.

* When we usually think of sand, we’re really looking at silicon dioxide, or “silica”. It’s basically a bunch of quartz crystals, broken down by erosion over the decades, centuries and millenia, into particles around a millimeter in diameter. Beaches are often a tan color thanks to iron oxide mixing in, but those tropical white-sand beaches come from calcium carbonate, i.e. the decayed skeletons of coral and other marine life. Some other beaches even have black sand, thanks to broken-down volcanic rocks washing ashore. Of course, those aren’t the only three colors possible, with nature providing spectacular grains the world over. Oddly enough, you’ve probably got sand in your kitchen right now... because of their grain size, sugar and salt technically qualify.

* Despite there being an estimated 7.5 x 10¹⁸ sand grains on Earth, it’s still a finite resource, since that erosion process takes so long to whittle all those materials down.

* Due to the natural shifting sands, it’s hard for most life to put down roots... but not impossible. Certain grasses can help sand dunes keep their hilly shape, and cut down on erosion overall.... though you’re much more likely to see that on the beach than in the much larger desert dunes around the world. Some crabs, snakes and lizards can also call the beach home, and it’s a crucial starting point for sea turtles, emerging from their nests to crawl slowly toward the sea.

* Human use of sand is nearly incalculable, from concrete and landscaping to porous soils for certain crops, to nearly every piece of glass you’ve ever seen. Even modern trains can shoot sand under their wheels for better traction in icy or wet conditions. Sand can also power imagination, of course -- who among us hasn’t made a sandcastle as a kid, only to watch our architectural hopes and dreams wash away with the tide? Chances are you’ve made nothing like this, though: The world’s tallest sandcastle came in at just under 70 feet tall in Denmark last year, and took more than 6400 tons of sand to create.

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