Hey, I'm Flor Lichtman, and you're listening to Science Friday.

Today in the show, the mysteries of sand dunes, including how to make them sing.

We create this very tiny sand avalanche.

And at that moment, if the conditions are right, your entire body starts to vibrate.

It's a very imposing feeling.

With September upon us, maybe you're thinking it's time to leave the sun and sand behind.

But we are not ready.

So today we're spending a moment on sand, in particular dunes.

From beaches to deserts, sand dunes are this important geological feature.

I mean, in some places, dunes protect the shore and, of course, the beach

houses behind them from the onslaught of ocean waves. In other places, the dunes themselves are on the

move, threatening homes and roads and even entire cities. Joining me now to sift out some

grains of truth about sand is Dr. Natalie Vrind. She's an associate professor

in mechanical engineering at the University of Colorado in Boulder. Natalie, welcome to Science Friday.

Thank you, Flora. I feel like most of us have known a dune, have met a dune, but not like you know dune.

So let's start with some 101 stuff. Like, what is the difference between a Dune and a big pile of sand?

Is there one?

Ooh, I'm not sure if there's a huge difference.

Like a pile of sand.

We've all been building them in our sand pits when we were little kids, right,

with our shovel and our little sift.

And a sand pile is actually just forming almost like a triangle if you look from the side, right?

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