Why Do Dunes Have a Gentle Slope on One Side and a Steep Slope on the Other?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why do dunes have a gentle slope on one side and a steep slope on the other?

The Big Idea

A dune has a gentle slope on the side facing the wind, and a steep slope on the other side! Wind pushes sand up the gentle side, and at the top the sand spills over the crest. The steep side is called the slip face.

Wind Pushes Up

Step one: wind pushes sand uphill. The wind blows sand grains up the long, gentle side of the dune. That side faces the wind.

Sand Spills Over

Step two: sand spills over the top. At the crest, the wind slows down and the grains tumble over the edge. They slide down the other side in little sandy avalanches.

The Slip Face

Step three: the slip face. The steep side stays at about the steepest angle that dry sand can hold without sliding. Its shape tells you which way the wind usually blows.

A Closer Look

Let's take a closer look! The wind comes from this side. It pushes sand up the gentle slope. The sand reaches the crest at the top. Then it slides down the steep slip face. Dunes are shaped by wind.

Quick Facts

Quick facts! A dune's steep slope usually faces away from the wind. Dry sand slides at about the same angle every time. That angle is usually somewhere between 30 and 35 degrees. Look at dunes from a safe distance, and never climb alone.

Think Like a Scientist

Now, think like a scientist! Make a sand pile in a baking pan. Tilt the pan very slowly. Watch the sand slide at one fixed angle. That angle shapes a dune's steep side.

Outro

Wind sets the shape of a dune, gentle on one side and steep on the other. Science is amazing! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!